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Heritage Eaters : Insects and Fungi in Heritage Collections Florian, Mary-Lou E 1997

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HERITAGE EATERS ag Insects & Fungi in Heritage Collections MARy-Lou FLORIAN HERITAGE EATERS HERITAGE EATERS ~g Insects & Fungi in Heritage Collections MARy-Lou FLORIAN P ublished by James & James (Science Publishers) L td , 35- 37 William Boad, London K"V1 3ER, UK © 1997 :'lary-Lou Florian T he moral right of the author has been asserted All rights reserved. :'\0 part of this book may be reproduced in any form or by any means electronic or mechanical , including photocopy ing, recording or by any information storage and ret rieval system without permission in writing from the copyright holder and the publishe r A catalogue record for this book is ava ilable from the British L ibrary ISIlN 1 873936494 P rinted in :'1alta by l nterprint L imited Contents J Introduction 1 2 Environmental parameters: their relevance in fungal and insect activity 5 3 Classification, naming and diagnostic features of common insect heritage eaters 13 4 Exoskeleton and moulting 19 5 The tracheal system 23 6 The insect egg 27 7 The larva: the eating machine 33 8 The pupa 49 9 Nymphs and their adults: environmental indicator species 57 10 The adult: trapping and monitoring 61 11 The insect infestation: finding, bagging, eradicating and clean-up 71 12 Insect eradication methods 81 13 Integrated insect pest control (npC) programme 105 14 Life cycle of conidial fungi 111 15 The sources of fun.gal conidia contamination on artifact materials 113 16 The conidium 117 17 Environmental factors in museums and homes which inlluence germination and vegetative growth of fungi 125 18 The fungal infestation 133 19 Eradication and control of fungal activity 145 20 Summary of fungal activity, prevention, collection recovery, preparedness and some disasters 153 Index 157 This book is dedicat.ed to our heritage objects Like ou rseh-es they t.oo are dust alld unto dust dlE'~- will ret.urn. 1-lowE'\·cr. J hope this book w ill help slow down t.he process For Illy grandchildren . .\Iolley. Joey and Katelyn 1 Introduction THE COLLECTIO'l FnEi'iZY The 19th-century enthusiasm for collecting heritage objects, both cultural and natural history items, has left us many problems. i\ever before have such large nwnbers of objects been brought together to be preserved - forever. Objects of curiosity from around the world were collected first, then artifacts from archaeological excavations, and nowa-days objects of OUf own natural and cultural heritage. The collecting phenomenon has been driven by our inherent curi -osity, our quest for knowledge of the world , our cultural aesthetic values and our need to connect personally with our past. Our first collections from the ancient world , archaeological objects, were mostly inorganic in nature and were not at risk from bi~deterioration by insects and fungi. Once objects made from organic materials were stored in large collections, diffi -culties emerged. \V ith manuscripts, documents and books stored in monasteries and librar ies, biodeterioration problems became rampant. Kow, the greatest threat is to natural history specimens collected to record today's biodiversity. " Te are no longer satisfied with just looking at objects. \Ye want heritage buildings and sites saved and often the objects in them used, or at least their use demonstrated, as in eco-museums. Keeping items in storage and on djsplay involves certain types of problem, but objects used in open areas present otbers. How can large collections, which are so vulnerable to insect and fungal deterioration: be protected, not only in storage and on display, but also in use? The compelling answer to biodeterioration problems in heritage collections is prevention. PROTECT ION fIl0~1 I,\"SECT A.\'J) FUNGAL HERI TAGE EATEIIS, T HE PR EVENTIVE APPROACH Cos mopolilan nalure of insect a nd fun ga l pes ts In reviewing the literature. one sees that there are only a few common insect pests found in museums, or in our homes. The species are cosmopolitan, occurring in museums all over the globe. There are some specific species in each environment, but the genera are represented worldwide. The insect species are those which seem to have become dependent on people and their life style, living in their environments and off their food materials. They often take advanrage of the human habit of storing food , as we ll as heritage objects. A smnmary from around the world of the fungi found on heritage objects also reveals many species in common . Four genera (Alternaria, A spergillus, Cladosporium and Penicil-lium) are found on all objects and in the air worldwide. This supports a common origin for the fungi contaminating herit-age objects: coming from airborne conidia during fabrication or during use. They are rare ly substrate specific. Prc"ention and c radication methods a l'e cosmopolita n The methods of prevention and eradication used against all the insect species are basically the same. \Vhen we encounter a clothes moth infestation, the eradication and prevention methods are the same no matter whether it is Tineola bisselliella, the webbing clothes moth, Tinea pellionella, the case-making moth or Trichophaga lapel::.ella , the tapestry moth. Our methods against Anlhrenus verbasci, the varied carpet beetle, Dermesles lardarius, the larder beetle,A uagenus megaloma. the black carpet beetle. or A nthrenus scrophulariae, the common carpet beetle, are as for the moths. The control of fungal problems is also the same allover the world. Fungi need a special environment for growth. A pre-ventive approach identifies such an environment, whether a microenvironment like a drawer, or a macroenvirorunent like a whole room , and controls it to prevent fungal development. Identifi ca tion of the species \Ye are rightly interested in the identification of the heritage-eating insects and fungi and carefully document this informa-tion, but usually the identification comes after the treaUnent. A permanent record of the activity of problem insects will be revealed if new species have presented themselves or if previously docwnented species have disappeared, increased, etc. Entomolo-gists are interested in distribution of species in nature: we are interested in the distribution of insect pests inside a building. Fungi may present a health hazard, so, in some cases where there is a massive infestation, species identification should be documented. Professional advice should be sought in these cases: the health of yourself, staff and the public should never be compromised. 2 H eritage Eaters \l a tc l' ial s of' hC"il agc objects \Ye are striving together to protect our heritage objects, no matter whether they are documents (ancient parchment, palm leaf or paper), woollen textiles, wooden sculptures or illsect collections. Heritage objects are unique to the cultures in which they wcre created but. fundamentally they all have the same materials and potential pests. These objects share, be~ sides their attacking insects and fungi, the materials constitut-ing them, primarily proteins, fats and cellulose, which are as cosmopolitan as the organisms consuming them. Biodeterioration of heritage objects is a universal problem with common parameters. Th e mi c rOCll v il 'O lllllcn t It is essential, but on its own not enough, to control the temperature and moisture in the air of a room. This is a macroenvironment. Insects and fungi are always in little microenvironments (unless, for example. there has been a disaster and e\'erything is wet). rt is these microenvironments we are looking for in inspecting entire collections or a few drawers. I t is the moisture and nutrientcontentofthe material that is critical for the survival of insects and fungi. So, besides controll ing the macroel1Vir0l11nent, we must find and solve the problems of the microenviromnents. Contl'o l methods It is in teresting to look at the historical de\'e lopment of the pest control measures. The earliest methods of protection were isolation and individual protection of objects, which were stored in special containers, such as cedar chests, sometimes using natural pesticides in the form of, for example, aromatic plants or woods. Grain was firststored in airtight buried chambers or under-ground silos. 'l'he insects and fungi present soon consumed the oxygen. The resultant anoxic environment prevented any further biodeterioration. The burial chambers in pyramids, in which precious funerary objects were preserved, may also have been oxygen-free. Today. anoxic environments developed by controlling the amounts of the atmospheric gases in airtight containers are being tested for eradication andcontrol of infestations of her-itage objects. \Y hen the technology of synthetic pesticides, insecticides and fungicidcs developed, they wcre hailed as the panacea to all biodeterioration problems and widely used. \\' e all, how-ever, know the story of DDT, and it is important to understand the abnormal reverence we gave these substances. They cer-tainly killed the pests. but we never considered the hazard to the object, to ourselves or to the environment. \ lethods are changing, because of our growing awareness of the influence of the cllC'micals a t these separa te levels. \ Ye are using methods that are 'environmentally friendly' and are not health hazards. but we have not thoroughly researched their influence on heritage objects' materials. Xew methods of control must be questioned and full answers obtained before they arc brought into use. TECII,\OLOG\ TIU'ISFEIl \\~e are always searching for methods. such as biological control, that will cause populations of insects to disappear. \\'e look to the stored food , forestry and agriculture industries and their de\'elopmcnt of such techniques. 'Because it works for the orchards and warehouses, it must work for us', is the attitude to this technology transfer. The main difference with our situation is that we have to eliminate every last one of the insects causing damage to our objects, whereas in other areas all they strive f('l' is a reduction in the insect pest population, never hoping or aiming for complete eradication. Csing pheromones is an example of jumping on a technol -ogy bandwagon. ' r hcse chemicals are of great value in forestry and agriculture but can also cause many problems, as they do in food storage. They attract insects that prey on the target insect and can also bring in the target species from other territories. Using pheromones for control in our field would require much more knowledge and assurance. T im e Another driving force in our control acti\'itics is time. \Ye all want a quick fix: methods of pr(,vention and eradication that do not take too long. ,\n integrated insect pest control programme involves time and dedication. \Ye must get beyond 'mass treatment syn-drome' and realize that the object for which we havc taken ethical responsibility often needs personal attention. Somc-times, for exam pIc, large numbers of objects can bc treated together for eradication of active insect infestation but then the follow-up cleaning of all the insect remains requires dedication to each individual item. This is essential because it is the only wa)" at a later date, to tell if the treatment was successful 01' if the object has become infested once again. Time is also required to assess the storage s ite in which an insect infestation has been found. It must be determined why the infestation occurred, where the insects came from, why there is a habitat for them there and how to prevent reinfestation. Time is needed to undertake inspections and monitor collections on a continuous basis. Pre\'ention is essential. Initially it takes a lot of personal time to eradicate infestations. survcy storage areas and design methods of prevention but, once it is done, a prcventi vc regime is eas), to maintain and is not so time-consuming. Even in the tropics, ",here massive infestations may occur, preventive mcas-mescan solve the problem, as long asall the basic work is done to rcach the stage of implementing the prevention programme. Ethical responsibility to he l' itagc objects An owner or other person caring for heritage objects has an ethicalrE'sponsibility to besure thatany treatment undertaken on an object will not destroy its aesthetic or physical integrity, cause any permanent deterioration or compromise its research potential. Conservators, who usually undertake treatments such as cleaning and frcezing, arc professionally bound by theircodeof ethics. Forcollection managers and curators therc fnlroduClion are also codes of ethics and elements in job descriptions explaining this ethical responsibi lity. Heritage objects cannot be used for treatment research. I t is not acceptable to expose them to treatments (incl ud ing those available cOlTul1ercially or proved in other fields), before these have been thoroughly' re-searched, to ensure that they can cause no harm. A \ ' ictorian dancing slipper is not the same as a new shoe. Counte,-ing mind-sets Objectivity is important in presenting information. An obsta-cle to achieving this is unawareness of entrenched mind -sets. which , unexamined, can cause fundamental problems. '\lost museum pest control publications, for example, have full biological details and wonderful illustrations of the adult insect but nothing on the larva, the heritage-eating mach ine. This is the result of a mind -set. Another example is found ,,·ith environmental monitoring. \Ye do an excellent job of moni -toring the air, but must realize that it is in the microenvironment, which includes the material of the object and its moisture content, that the problem lies. In discussing fungal problems, we consider the environment that is condu -cive to the vegetative growth of the fungus, but tend to overlook the germination of the conidia that initiates infesta -tions and it is this we should be concerned about ~ another mind -set. A final example is our cultural Ileed to identify emotionally with the heritage items in our care, but we thus fail to treat them as compositions of organic materials. I n facing, as we must, the challenges posed by their materials , in no way ~o we forget the preciousness of the objects and our ethical responsibility towards them. THI S BOOK'S Co;\THIBLTIO, The book's subject is the problems that insect and fungi pests present to those keeping heritage objects in a variety of storage areas ~ museums, historic buildings and homes ~ and its goal is to provide the information necessary to sol\"e these problei lis . Because each collection , with its environment, is unique, standard procedures cannot be recommended. A broad under-standing of all the parameters ~ the heritage eaters, material of the heritage object, environment of the storage area, extent of the infestation, nature of the collection and staff availability ~ is needed to design treatments and preventive procedures that will ensure the objects have the protection they require. Readers are encouraged to develop procedures for their spe-cific problems. The book isarrangcd within its major sections on insectand fungal heritage eaters into discrete units, or chapters. each of which stands a lone with its own references. Following the introduction is a review of pertinent infor-mation on environmental parameters and their influence on the insects and fungi. The emphasis is on the moisture in the materials of heritage objects, hecause of its major contribution to the support of the organisms. An introduction to insect classification and life cycle pat-terns related to the insect species commonly encounted in infestations of heritage objects illustrates the taxonomic rela -tionships of this small group of insects. The physiology of insects is a gigantic topiC'. This book is not intended to be a biology text book, thus only two aspects of physiology are discussed as separate units. the tracheal and exoskeleton system. These two are re \"iewed because of the ir importance in reference to eradication methods which di -rectly influence these life-depe ndent systems. The two sys-tems arc the most vulnerable to damage and are the most important systems for survival because they maintain neces-sary oxygen and body water. Chapters on the egg. larva and pupa of the beetle and moth , revie w their structure, identification. physiology and biology which is pertinent to identification of and understanding prevention and eradication of insect problems. The nymphs and their adults are presented separately because, unlike the beetles and mot hs , they do not have lan"al and pupal stages. They li\'e separatply from where they feed and their presence indicates building environmental prob-lems. Termites are not discussed in detail in this book. The fact that the city of Palermo in Sicily is built on a termite colony illustrates the enormity of the problem. Termites are essentially a building problem but free-standing objects that are infested are included in the discussion on wood beetle damage. Information on adult beetles and moths is presented in reference to monitoring methods, because it is this life stage which is captured in the monitoring traps. Information on the monitoring methods is discussed in reference to the physi -ological responses. light wavc sensitivity and pheromone pro-duction of the target adults . The pros and cons and suggestions of use are presented. .\ chapter on the insect infestation presents information on how to inspect heritage objects in order to find the infestation . Procedures for enclosing and moving the infestation so as to prevent its spreading and eradication treatments are sug-gested. Analyses of evidence of insect activity is presented to assist in identifying the causative insect. A thorough re\"iew of eradication methods' (temperature extremes, anoxic environments and others) influence on the insect and the heritage object material is presented. This information isessential because the treatments are interventive treatments. Information on how to establish an integrated insect pest control programme, a preventive programme, is presented. The programme can be designed for a chest of drawers or a museum storage area. The approach is the same but specific procedures must be developed for each unique space. The reader is encouraged to develop procedures for their specific problem . . An example of a programme is presented as well as the real-life difficulties often encountered when establishing a preventive programme. The first chapter on the fungi gi\"es a simple description of their life cycle. The cosmopolitan nature of the conidial fungi which produce the surface growth on heritage objects is illustrated. The importance of the conidia is emphasised. in reference to causing fungal spots or infestations. The physiol -ogy of the break ing of the dormancy of the conidia, activation , is discussed in reference to the potential activation by conser-vation treatments as well as by moisture or inherentchemicals in the material. 4 H eritage Eaters The environmental factors, their influence on the mois-ture in materials and the state and availability of the water to the conidia and vegetative growth of a fungal colony is reviewed. A new approach to analysis of fungal infestations is pre-sented in the chapter on the manifestation of the fungal growth and its relationsh ip to the methods of containment. The fungal infestation is also looked at in reference to w hat is actually present in the infestation: the fungal structures as well as their chemical make up and the metabolic products of vegetative growth. Eradication methods are d iscussed in reference to their success and their effect on the organisms and the materials of the heritage object. Suggestions of removal of funga l infestations or collection recovery, pros and cons of degree of success, influence on the organism and materials of the object and health hazards is outlined. T he importance of preparedness in theeventof disasters which result in extensive fungal infestations is emphasised. Again the goal of the book is to give the reader the informa-tion and the encouragement to pursue information w hich is requ ired to under take logical eradication and preventivemeas-ures against the heritage eaters, insect and fungal pes ts. PRE\' EI>T IOi\" rOil T HE FUTLIlE T he information in this book provides just a t('lste of the state of current knowledge. \Ve know a great deal, but there re -mains much to be discovered . In the future treatment and storage methods for heritage objects may change rad ically but, in the meantime, prevention is the key to protecting heritage objects fro m biodeterioration. 2 Envirollll1.ental Param eters: their Relevance in Fungal and Insect Activity The purpose of this chapter is to introduce the basic concepts relating to environmental parameters - rad iation, light and temperature; the water in air and relative humidity ( lUI ); the water in materials and equilibrium moisture content (E'\lC) of m aterials; interactions between R H and E.\l C and dust. and to emphasize t he relevant aspects influencing fungal and insect activity. 2.1 ~ IA CROE"'\, I RO.'l ,\I EYrS Ai\'D ~ II C ROEi\'Yl HO,\~1 E'iTS T he environment in a room is a macroenvironmen t, of which the ambient air is the major component. \Ye usually monitor the temperatu re and HJ I of the ambient air in rooms an d feel compla~en t. But the re are many microenvironments or local areas, around, in and on heritage objects, such as drawers, boxes, bottom shelves, the lowest piece of paper in a pile, in which the environm ental parameters va ry from the ambient macroenvironment. The importance of microenvironments is often overlooked but t hey have a major innuence on the behaviour and life cycle of insect 'lnd funga l pests, as well as on the organ ic mater ials of the objects . .:\early all insect and fu ngal act ivity in museums and in h omes occurs in microenvironments. O nly when the re is a majo r macroenvironmental breakdown or disaster, or when an ini-tial infestation is neglected, is a whole room or large area involved. 2.2 RADlAT 10i\' EFF ECTS 2.2.1 T he lig h t of lig ht Li ght in our homes and m useums comes fro m the sun and from ligh t bulbs. Light is made up of h igh-energy rad iation consisting of photons, which move in a wave. Photons have different wavelengths (T able 2. t). Brill (1980) showed the size re lationship of this radia t ion and convers ion facto rs for other units of length Cf able 2.2). T he shorter the wavelength , the stronger the energy of the photon . \ Ve can see only wavelengths of 400- 700nm, the visible light. but our bodi es respond to the Table 2. 1. NJolecular evenlS induced by various wavelengths of radiation (Brill. 1980). Wavelength Frequency (Hz) Region name (3 x 10' )-(3 x 10;)m 1_ 103 Power (3 x 10;)-300m 1 0l_ 1 0~ Audio 30G-3m 106_ 108 Radiowave 3- IO-lm 10' -(3 x 10" ) Microwave IOs-700nm (3 x 10" )- (4 x 10") Infrared 700-400nm (4 x 10" )-(7 x 10") Visible 40G- IOnm (7 x 10" )-(3 x 10 " ) Ultraviolet IQ-().03nm (3 x 1016)_10 19 X-ray 0.Q3 (3 x I O~)nm 10 1'1 lOB Gamma-ray T able 2.2. Conversion faclo rs fo r unils of lenglh ' (after Brill, 1980). Response of atoms and molecules None None Molecular translations. nuclear reorientations Molecular rotations, e lectron reorientations Molecular vibrations and direct heat effects Low-energy electronic transitions in valence shell High-energy electronic transitions in valence shell Electronic transitions in the inner shell, diffraction by atoms Nuclear transitions Multiply num ber of ~ Angstroms Nanometres Micrometres Millimetres Centimetres Metres (m) by (N' ('1m, m~) (~. ~m) (mm) (em) to obtain number of ~ ~ Angstroms (Ao) 10 10' 10' 10' 10 10 Nanometres (11m, mil) 10-1 I 10' 10' 10' 10' Micrometres (11 , 11m) 10~ 10-3 I 10' 10' 10' Millimetres (mm) 10-7 1 0~ 10-1 I 10 10' Centimetres (cm) 10-" 10-7 1 0~ 0.1 I 10' Metres (m) 10-10 10-9 1 0~ 10-l 10-1 I • Note that micrometres (11m) are sometimes referred to as microns (1-1 ) and nanomet res (11m) as millimicrons (mil)· 6 l-Ierilage Ealers high-energy, short ultraviolet waves (below 400nm) and the low-energy, long infrared heat waves (above 700nll1). \Ve are aware of the damage from ultraviolet rays and infrared heat waves. but any ligh t can cause deterioration to the materials of heritage objects (Brill, [980). Photons that hit the surfaces of objects may be reflected or absorbed. depending on the surface colour. If absorbed, the photons hit molecules of the material and change the elec-tronic state of these molecules. H the photon is released from the molecules and the energy converted to heat, there is no light damage, i.e. no fading of colours. 1f the photon is not released as heat and itremainsin the material in the form of high-energy radicals, lhese react with oxygen and water and cause the formation of peroxides, which cause colours to fade and initiate the destructive chemical reactions of photo-oxidation. L ighting in museums is most important ill display and work areas, where heritage objects are exposed to the light for long periods of time. Tn these cases the light intensity, the heat (infrared rays) and the ultraviolet rays t he light em its should be measured and controlled (;'\I ichalski, 1989). For further information, see Brill (1980), .\lichalski ( 1987) and Thomson (\986). 2.2.2 T c mpe ,'atur'e Temperature is the degree of hotness or coldness, as measured on the centigrade or Fahrenheit scales. The centigrade (Cel-sius) thermometer is divided into 100 units between the freezing point (OOC) and the boiling point (100°C) of water. The Fah renheit thermometer reading of 32°F corresponds to OOC and 212°F to IOO°e. D ifferences in temperature are a result of the presence of different amounts of heat. Heat is the result of infrared heat radiation or rays Crable 2.1) emitted from a light source such as burning fuel, an incandescent light or the sun. An increase in heat causes an increase in the rate of rnove-mentof molecules, wllich is expressed mainly as an increase in the rate of chemical reactions. Vapour pressure, the volatili ty, of water is influenced directly by temperature: an increase in the vapour pressure of water results in an increase in water vapour's rate of movement, in or out of organic materials. I nfrared rays can penetrate opaque su rfaces, heating materials internally. This is the basis of infrared photography, which allows one tosee previous versionsof a painting under the final painted surface. T he temperature of ambient air in rooms, in macroenvironments, is controlled by air conditioning, cooling or heating, and may be influenced by outdoor temperatures. T emperature changes occur in microenvironments because of the diffusion of heat from small heat sources, such as radiators, light bul bs, electrical appl iances, sunlight, stratification (warm air rising and cold air moving downwards), limited air circu-lation or the infrared absorbency of the material of the he r it-age object. .\1aterials absorb heat according to the colour of their surface. A black surface absorbs infrared rays froll1 a light source and a white surface reflec ts them . Thus the colourofthe material of the heritage object, or materials adjacent to it, e.g. a container or display mount, will influence the temperature ' in the microenvironment of the object. 2.2.3 Effects of radiations on herilage ealer's \ Ve are concerned about the effects of tem perature on heri tage objects, but we must also be aware of their influence on insects and fungal pests. A general rule is that growth occurs from about 4--37°C, with optimum growth around 20°e. Infrared absorption on ma terial surfaces may create a condu-cive m icroenvironment for insect and fungal pest activity due to an increase in local temperature. Light plays a role in the behaviour of insects and in the growth of fungi. Larvae shun light, whereas some of the adults are attracted to it. Some adul t insects can see infrared and ultraviolet rays. Ultraviolet l ight traps arc used successfully in orchards and forests to attract adult insects: the insect sees the ultraviolet ligh t as sunlight reflecting off t he ground of open spaces. (This is discussed in more detail in 10.2.) Some devel -opmental aspects of the growth of fungi are also influenced by light. Some species of fungi, when subjected to light, produce pigments, while others are unaffected. 1n microbiology, ultraviolet rays have been used to kill micro-organisms, but the levels used would damage the or-ganic materials of heritage objects. From even this little information it is obvious that the microenvironmen ts of heritage objects may support insec t and fungal activity while the macroenvironment does not. 2.3 WATEB VA POU B IN A IR 2.3.1 Holding capac ity of ai" The hold ing capacity of air is the amount of water thata given volume of air can IlOld at a given temperature and pressure. Air tern perature influences the water-holding capacity of the air, as shown in the hygrometric chart (Figure 2.1). The act ual amount of water in a given volume of saturated air varies with temperature: more at higher temperatures and less at lower. \"hen the temperature of air is increased, the air expands and there is more space between the gas molecu les for water to enter as water vapour. \Vhen th e temperature decreases, the air contracts, the gas molecules are more densely packed and there is less space between them to which water can attach itself, so the holding capacity of the air is decreased . Dry bulb,~mp~nture('C) Figure 2.1. Hygromelric charI: reLates the temperature cf th.e air in a room (dry bulb temperalure) 10 iiS IVi and absolute humidily (after T h.omson. 1988). Em,ironmel/tal parameters; their relevance inJungal and insect activity \Yater vapour mo\'es into the air from adsorbent materials (see 2A.2 for explanation of adsorb and absorb), water bodies, etc .. according to a diffusion gradient, from a region of high concentration to a region of low concentration. until an equi-librium is reached, If the air has all the water it can hold , i.c. is at 100°'0 of its holding capacity, ata specific temperature and pressure, it is saturated. Above saturation, it will rain. The water in the outdoor air comes from water bodies, clouds and organic materials. In buildings housing heritage objects it comes from the organic ma terials of the heritage objects. air-conditioning units and people. \Yhat is the relevance of the holding capacity of air to insect and fungal growth? As one example, when there are tempera-ture changes, specifically reduction in temperature, the hold-ing capacity of the air is decreased and the excess water vapour goes into organic materials. The more moisture in materials. the greater the potential of insect or fungal att.ack. Another example is when infested heritage objects in polyethylene bags are placed in freezing tempera tures for insecteradication (sec 12.1). It is important to know that, as the air in the bag around the object cools, its holding capacity is reduced. The excess water \-apour is adsorbed into the materials of the object: it does not form frost or condense on surfaces. 2.3.2 He lal ive humidil~' (HI! ) 2.3.2.1 111'--1."1 Rl\e lUi Temperature and Rlt of air are so closely linked that one cannot be discussed without the other. RH is measured as the percentage of water vapour in a given volume of a ir relati\'e to its maximum holding capacity. Thus, at a given temperature. lOoe (see Figure 2.1), a cubic metre of air has a holding capacity of 17g of water: it is 100% saturated . But if there is only 8.5g of water in the cubic metre, which is 50% of what it could hold, its Ri l is 50°'-0. In an empty, closed system, i.e. a sealed showcase. with no new water vapour entering, tern perature alone can alter the RI I and the amount of moisture in the air will be the same. For example, for a cubic metre of air with 8.5 g of water: • at 25°C, the H.I I is 37°"0; • at 20°C, the Rl i is 50%; • at 15°C, the Rll is 68%. If the showcase were filled with adsorbent objects made from cotton, leather and wool and the abo\-e temperature changes occurred, there would be very little change in the RII in the case, e\'en if the seal was broken and outside moisture entered the showcase. The reason is that the adsorptive organic male-rials act as a buffer preventing lU I fluctuations by adsorbing moisture when the R I I rises and gi\' ing off moisture when the R It falls. This explains the buffering reaction of wood that is often used to maintain constant H. II in display cases and transportcontainers(Stolow, 1966; Thomson, 1986; \\'eintraub, 1981). Silica gel is a common buffer used in many situations in museums(1 ,a Fontaine, 1984;Stolow, 1966), homes and indus-try to maintain a constant RI I in packages. containers, cases, ('tc. containing moisture-sensitive materials. 2.3.2.2 ()P/~ \ -/\/J CI.mE/J f~ \f IRO\ llE\TS \Ye often try to interpret aspects or indoor environments from personal experience. Our environment outdoors is an open system. not a confined system like a building, room or freezer chest. Besides experiencing hot, humid days, we have also felt how dry the air seems when the temperature outdoors is freezing. Actually, cool air should feel damp but, outdoors, freezing ai r feels dry. Three things happen to make the air dry: Because of the low temperature the holding capacity of water vapour in freezing air is low. 2 J n the open system outdoors, water vapour condenses on cold surfaces as frost or forms ice and water va pow' is withdrawn from the air. 3 Organi c materials adsorb more moisture at low tempera-tures, withdrawing water vapour from the air. Thus the freezing cold air holds less water vapour, there is less water vapour available and the IU-I can drop dramatically. \Yhen this cold, dry air comes into our furnaces or air-condi-tioning units and is heated, it feels drier, and is drier. The example of air conditioning illustrates this. \Vith air condition ing. there is always a need for outside air, replace-ment air, to come into the building. rr replacement air from outdoors is at O°C with 1.8g of water and HI I 50%, when heated to 20°C the lUI decreases to 20%, and that's dry. In some heating units water vapour is added to compensate for this dryness. The hot, humid and the cold, dry days are examples of an open system in which the air has no limit but the atmosphere. :\!useums, heritage houses and your home are basically closed units and the amount of water vapour held in the air depends not only on the temperature but on how much water vapour is available. \Yater vapour comes from adsorbent materials, air-conditioning units and people but. with sophisticated air conditioning in buildings, the amount of water vapour is controlled by dehumidification and humidification units. 1 t is in this outdoor, open-air system orhot. humid and cold. dry days that the ancestors of our insect and fungal pests evoh'ed. Their behavioural and physiological responses are still based on th is open system, even though they have adapted to buildings. The key to this adaptation is their ability to enter periods of low metabolic activity, quiescence or diapause. and wait for u~ to inadvertently cause conducive indoor environ-ments to occur. \\'hen this happens, they hurry to take advan-tage of it. .:\lany endemic beetle species that are pests in museums, even though they do not see the light of day or feel the daily and seasonal fluctuations of temperature and humid -ity. still go through seasonal pupation times. 2.3.2.3 IlRl.Hf .1\('£ TO IIERITIGE EtTERS' ICTtI rn The interrelationship of organic materials , temperature and lUI to pest problems is reie\'atlt. Outdoors, insects respond to temperature and 1l10isturechangesand have complex feedback mechan isms that can trigger development. For exam pie, some pupal cocoons can adsorb moisture from the air, which will ini tiate ad ult emergence or, as another exam pie, the conidia of fungi may need fluctuations of temperature and moisture before they can germinate. These feedback mechanisms can 8 Heritage Eaters also occur in buildings with temperature and RH changes, which ca use adsorption and desorption of moisture in insects as well as in materials. :\ l ostoutbursts of insect pesland fungal activity observed in buildings have occurred after some e nvironmenta l change, which suggests that there is a real interaction. A scenario: .i n a large museum , one Christmas ho liday, the floor maintenance crew thought it would be a good idea , while the staff were away, to strip off the wax from the floors of the ir offices, on all 14 floors , and apply new wax. This was a water cleaning process. T he chief conservator was informed only on return from the holidays, by reading the hygrothermographs ofthat week. The RH change was dramatic but short. T welve to fourteen days later an unusual number of va r ied carpet beetle adults appeared on the window light traps. The popu -lation peaked and waned in a few days. T he computer record of previous years did not show a population peak for this time of the year, so it can be assumed that it was caused by the dramatic increase in RH. For further information on water vapour in air and RH , see La Fontaine and ~ I ichalski ( 1984). ~J ichalski ( 1994) and Thomson ( 1986). 2.4 IVAT EH IN ~IAT ER I A LS 2.4.1 Equ ili brium moisture conte nt. (Ei\ IC) of organ ic mate r'ia ls I n discussion of RH, adsorptive organic materials had to be included because of their role in buffering RH Ouctuations. Organic materials of heritage objects, if exposed to an environment containing water vapour , will eventually arrive at a steady-state moisture-content condition, called equilib-rium moisture content ( EM C) . T he E:\ IC de pends on the RH and tempera ture of the surrounding air, and physical condi-tions in the material. It fluctuates with change in either RH or temperature or both. Figure 2.2 shows how the EMC varies with te mperature and R I L changes. General principles are that an increase in temperature decreases the E:\1C and vice versa , and increasing the RH increases the El\ IC and vice versa. I t is possible to maintain a constant E;\ JC in a material by altering both temperature and R H . 30 / -700r V / 0 141"---, :/ / I ,......, / / . - ~ ~/ / / ~ / / / 0 -c--~ 1--;;" , ~ ------/ ;:-:-~ I--I--0 /", 20 40 60 80 100 Relative hUmidityofatmospherl!. % Figure 2.2. Sorption isotherms fo r wood at three temperatures (from Panshin and de Zeeuw, 1970). rr there is more moisture in organic materials than in the air, there is a d iffusion gradient and the moisture will diffuse out of the materials into the air. T his is simply the d ry ing of mater ials. E ventually, an equil ibrium will be reached at which equal amounts of water vapour move in and out of the mate rials . .If the temperature of the air decreases, the excess water in the air diffuses into the mater ials until , again , an equilibrium is reached . The water in materials in equilibrium with that in the air is the E:vl G. This refers to the amount of moisture in a ma terial at equilibriwn with a specific RH and tempe rature. \Vhen materials are oven-dried t " e weight lost is the E;\ l C and represents all the moisture, bound or free, in th e materials. I n d,y organic materials. such as wood, the EMC is its water content measured as a percentage of d ry weight. T his wate r is called Ei\ IC because some of it moves to reach equilibrium. weight of water X 100 = % ;"\ l C of oven-dry weight dry weight E x ample: wet weight dry weigh t weight of water lOX 100 100 = 110g = 100g = 109 = 10% MC of dry weigh t or 10% EMC \Vater in living materials is usually m easured as a percentage of body weight (which may also be called live weight or '>vet weight) . weight of water X 100 wet weight Ex ample: wet weight dry weight weight of water 90 X 100 100 = :\IJC as % of body weight = 100g (weigh t of an individual) = 109 = 90g = 90% water of body weigh t. live weight or wet weight T he movement of this water in a living organism is controlled by life processes and is not d irectly influenced by HH or temperature. POI' further information on EMC, see Panshin and de Zeeuw ( 1970) and Thomson (1986). 2.4.2 ~ I O I STUHE IN OHGAN IC I\lATEH IALS -FIl EE, S UHFA C E ON SUHFACE AND BOUND Organic materia ls can adsorb just so much moisture. The amount depends on their chemical and physical structure. For example, woods can only adsorb water vapour up to 28% Ei\ IC of their dry weight- Over this amount, they become wet. T he El\ JC water is in molecules in cell walls, associated with chemicals and other water molecules.lf the wood is wet the re is free water inside the lumen (central empty region inside u1e wood cell). Environmental parameters: their relevance inJungal alld insect activity 9 ~ 30 ... z \oJ ... ~ u '" i 20 ~ ~ ::; :; d 10 \oJ RELATI VE HUMIDITY 1'/01 The water involved in this 28% LVIC has different physical forms according to its attachment in the materials. This is shown in F igure 2.3. Some water m olecules are bonded by strong chemical bonds to the molecules of the organic mate-rial, i.e. cellulose, protein, etc. T his is called bound water. Some water molecules are bonded by weaker hydrogen bonds to the Sill' faces of the these molecules and some water is attached to other water molecules by very weak electrostatic bonds (multi -layered water). The water that wets materials is free water in the pores or capillaries and lumina of cells of the materials. All the water, except the molecularly bound water, is adsorbed water. Adsorption is a special type of absorption in which surfaces act as the absorber. Absorption is the wliform penetration of one substance into another by chemical or molecular action. Radia-tion, gases, heat, chemicals in solution as well as fluids in biologi-cal systems are absorbed because they are involved in chemical or molecular reactions. VVhereas water, water vapour and chemicals that are on surfaces of animal and plant fibres, coLloidal and crystalline polymers, chelators and such chemicals as charcoal are adsorbed to the surface. Fibres have many levels of adsorbing surfaces, from micro and macro fibrils to the complex fibre. For further information on moisture in organic m aterials, see Rockland and Stewart (1981). 2.4.3 Sequence of wa te r r e mo va l w ith drying VVhen wet wood is oven-dried, the water is removed in a sequence reflecting the strength of its bond attachment to molecules and surfaces in the material. tree water is the fir.st to go. I t is free in the lumina of the cells or capillaries and takes the least energy to remove, coming off rapidly by evaporative drying. The wood is now below fibre saturation poin t (28% EM C) and feels dry. If the drying of this relatively dry wood is continued, the next water to come off is the multi-layered, electrostatically bonded water, which moves freely in and out of the material according to the R l-I changes in the air. / / /' Figure 2.3. If/ater vapour adsorption. curves oj Merino wool. The top curve shows the processes as a result of the three curves: A is bound waler adsorbed by strong hydrophilic bonds, B is monolay er water adsorbed by weak hydrophilic bonds and C multi-layerformalion by weak hydrogen bonds (after I,Vall, 1980, originally from D'Arcy R. L. and (Fall I C. 1963. Trans. Faraday, 66, 12J6). As the drying process carries on: the next water to be removed is that bonded by hydrogen bonds. Th is ,,'ater takes heat energy equivalent to the strength of the bonds to be released. Finally, the last water to come off, and hardest to remove, is the chemically bound water. The multi-layered, electrostatically bonded water and the hydrogen bonded water are th e only types of water that move to reach an equilibrium, but we use the term E:\ IC to include all the water in materials. 'vVeight changes in organic materi-als occuring during small fluc tuations in the environment involve only these weakly attached types of water. Only free water and some of the weakly bonded multi-layered water are available for the growth of micro-organisms and most insect pests. 2.4.4 Hyste l'ica l hys te l'es is "Vhen moisture is adsorbed into materials because of an increase in RH ,and then desorbed because of a decrease in RH , the rate of desorption is much slower than the rate of adsorp-tion . The graph in Figure 2.4 shows that the process of adsorption has a lower E:\I{C than when in the process of desorption (drying). This normal characteristic of organic materials is called the hysteresis sorption curve. I t is important to be aware of the process of hysteresis when drying wet materials. Even if they have come to equilibrium with ambient conditions, they may still have a much higher ElVIC than we expect, which could make them vulnerable to insect and fungal attack. This is also the case when a hUJl1idi-fication treatment has been userl. to soften materials for ma-nipulation. In the freezing process for eradication of insects (Florian, 1986), the organic materials subjected to the temperature reduction will adsorb water vapour, resu lting in a small increase in E:\IJG. 'vYhen the material is removed from the freezer and i t reaches equilibrium with the room temperature, 10 H eritage Eaters ON :x: 0'-"1 20] .. 10 / .... J .... / ~\O "" ........ I // I E,SOR f'_- :/' ., ,..0'500 I I I 0rO--- ~"'0"1 //' I O~, ~r--r~r-.--.--'-~--.--r--r-0 .0 0.1 0 .2 0.3 0 .4 C. !! 0.6 0 .7 0.8 0. 9 1.0 WATER ACTIVITY Figure 2.4. Schematic representation oj a moisture so'ption hysteresis loop. IVater activity can be converted to 0 to 100% RI-J (Kapsa lis, 1987). (For an explanation of waler activity see section 2.4.6) it will lose, desorb, most of the wa ter vapour it adsorbed. T he E;\. l C will be higher than when it was put into the freezer because of hysteresis. Eventually, the original equilibrium will be reached. For further information on hysteresis, see Kapsalis ( 1987), Rockland and Stewa,t ( 1981 ), Troller and Christian (1978) and Watt ( 1979) . 2.4.5 Rega in Regain is a term describittg the adsorbency of materials. Old materials tend to be briltle alld dry. Over time, materials are exposed to many f1uctuatiolls in gain and loss of moisture due to environmental fluctuations. Each time a loss occurs, some of the organ ic material 's molecular bonds, which would normally v o P/Po Figure 2.5. Scanning paths of repealing adsolplion and desorption curves in hysteresis (after Kapsalis, 1981). P / Po = waler activily aw or % R H , V = equilihrilllri moisture content (ELVIC). Table 2.3. Percent equilibriwn moisture conlent (EMC) of different materials held at 50% RJ-i and 100% RH, shown to illustrate the different adsorbency of materials (Florian, 1986). Mate rial Temperature (0C) EMC (Reference) 50% RH 100% RH Unmodified merino 35 11.3- 12.3 34.2 wool ( I ) Methylated wool 35 46.0 (79%) ( I) Collagen (2) 35 15 55 Merino wool (3) 20 I I 35 Merino wool (3) 65 9 31 Me rino wool (3) 100 7 28 Wool (4) no data 11- 13 35 Cotton (4) no data 5.5- 6.5 23 Jute (4) no data 8.5- 11 35 Cellulose acetate no data 4.5- 5 17- 18 rayon (4) Viscose rayon (4) no data 11- 12 40 Cuprammonium no data 11- 12 40 rayon (4) Nylon (2) 35 4.5 10 Nylon (4) no data 3.5-4 8 Silk (4) no data 7.5- 8 30 Wood (5) no data 9 31 Silica gel , grade 03 (6) no data 30 3S Si lica gel , grade 59 (6) no data S IS • no data - assume 20°e. References: I. Watt (1979). 2. O'Arcy and Watt (198 1). 3. Watt (1980).4. Carlene ( 1944). S. Hoadley (1980). 6. La Fontaine (1984). hold water. bond instead to each other (cross-link).\'Vater can no longer fit in and the material becomes stiff and dry. T hese old mater ials have t hus lost some regain ability. T he hyste resis sorption curve has become smaller and smaller, as is seen in Figure 2.5 . This mater ial has a reduced El\l C and is consequently more resistant to insect or fungal attack. \Vood from different species or different types of leathers, textiles or papers, at the same RI-J and tem perature, may each have a different EMe. Table 2.3 g ives examples of the EMCs of a variety of similar and dissimilar materials. The moisture content of the materials is dependent on their many character~ istics, i.e. physical structure or porosity, inherent chemicals and those used in manufacture or during use, deterioration and the sorptive histo ry. P hysical characteristics are: available hydrogen bonding sites; protein denaturation; degree of poly ~ mer crystallinity or amorphous regions; and available surface area . Chemical alterations are caused by: tannage; alkylation; acety lation; deamination; and humectants. Deterioration can involve mechanical breaking, physical shr inkage, and ox ida ~ tion and photochemical degradation. The sorptive h istory of materials is a result of successive adsorption and desorption cycles, which may resu lt in loss of hysteresis and reduced moisture regain, and changes in molecular structure. There are many other possible alterations to materia ls. At the same RII and tem pera ture, some m aterials will have enough moisture to support fungal activ ity and others will not, another example of a microenviron m ent. The m aj or influe nce on the rate of development and the activi ty of insects and fu ngal pests is moisture in the materials, the substrate on wh ich they are growing. The role of the microenvironment in supporti ng pestacti v ~ ity isoften overlooked in the assessment and prevention of pest Environmental parameters: the l:r relevance infimgal and insect activity 11 problems. The logical approach in evaluating vulnerability is to examine the range of E:\ ICs reported for the different groups of materials under scrutiny. 2.4.6 ' \ Vate r , watc r', e "c r'yw he r'e. Nor' a ny dr'op to (lJ' ink ' Some chemicals, when added to materials. increase their moisture content but not their vulnerability to heritage eaters. In the organic material of heritage items there are some-times water-soluble chemicals, either inherent 01' added dur-ing use or treatment, that change the vapour pressure of the water. For example, a water solution of glycerine is often used as a humectant to keep objects soft and pliable. The glycerine lowers the vapour pressure of the water, as the water is strongly bonded to the glycerine molecules and cannot move according to changes in the R H and temperature of the air around it. There may be a great quantity of water in the material but fungi cannot 'use it because they cannot compete with the strength of the bonds between the glycerine and the water. The glycerine changes the vapour pressure of the water or, in other words, alters the water activity (a) (Rockland and Stewart, 1981 ): aw is an expression of the ratio of the vapour pressure of the water in materials relative to pure water. thus it ranges from 1 to O. Pure water hasa high vapour pressure and easily evaporates, but water mixed with sugar or salt has a low vapour pressure and it takes extra energy and a long time to evaporate. :\lost fungi cannot utilize water below aoo 0.65. (\Yater activity and fungi are discussed in detail in 17.1 ). In the fungi physiology and food industry literature, aU} is used to describe water in materials. 2.4.7 The heal of we tting Adsorption is an exothermal reaction. \Vhen we go outside on a damp, cool day with a wool coat on, the wool will adsorb moisture from the cold air and become warm. The adsorption of the water in the organic material is an e xothermic reaction which creates heat. The opposite happens when water is evaporated, an endotherm ic read ion.It uti lizes heat for evapo-ration; for example, when we sweat our body heat is utilized in evaporation and the heat loss cools our skin. These exothermic and endothermic reactions, caused by adsorption and desorption respectively, occur in the organic materials of heritage objects during fluctuations or£:\ IC. This phenomenon, which changes the microenvironment, is com-monly overlooked when we examinethe vulnerability of these materials to insect and fungal damage. Could the tempera -ture/ E:\ IC cycles be involved in breaking dormancy or quies-cence in insects or cause activation of the conidia of fungi? \Ye are aware that the heat of wetting causes shrinkage in badly deteriorated leathers, and use this as a method of determining deterioration , but we do not consider it on the micro-level of insects and fungi. 2.4.8 Il e r' ilage ea te r's do not d r'ink wate r' The water in materials influences their vulnerability to biodeterioration by insect and fungal heritage eaters. Tnsects may obtain some water vapour from the air they breathe, but there is no strong evid ence that fungi adsorb water vapour from the atmosphe re. Thus they are dependent on the water in the materials they eat. Pungi give off e nzymes dissolved in their cy toplasmic wate r, but they will reabsorb this water, as well as some substrate moisture, with the digested nutrients. Some insects. for example booklice and some wood -boring beetles, feed on living fungi growing on materials and benefit rrom the ability of these fungi to remove water from the substrate. Some stored grain beetles can live on dry grail~ , with less than 5% E:\ IC, by using the bound water in the cellulose and starch molecules of the grain as a source or water. Organic materials with a high moisture content must be texturally easier to chew, which would make them more attractive tosome insects. The bottom line is that water is needed for life. Even if the RH around a maLerial is not conducive for growth, if the material has sufficient moisture it will support pests. \Yith our tunnel vision we always look at the influence of the ambient air R H on the growth and development of pests and overlook the influence of moisture in the materials them -selves. In the food industry moisture in foodstuffs is controlled to prevent fungal activity. In the lumber industry wood is kiln -dried to lower the E;\ rC and protect it from specific wood-attacking beetles. Anyone with experience in maintaining an insect colony knows how critical it is to maintain just the right rnoisture in the materials on which the insects are feeding. "\~e do an excellent job when documenting heritage objects of recording information about the type and condition of the materials. but .we rarely note their weights - unless they are made of gold. \Ye should be recording the weight of objects. plus the RJl and temperature at the time of weighing. T he Rl-l and temperature may vary but the three pieces of information, taken together, will be significant. Over time, a number of weighingswill tellusaboutregainchangesand maybea valuable reference point for drying objects after accidental wetting. T hereare. unfortunately, no easy, non-destructive methods of determining the E:\ l C of our priceless heritage items. X-ray densitometry and determination of electrical resistance are two non-destructive methods used to determine moisture in wood , but these are nOl suitable for heritage objects because they are either damaging or give information only regarding the one spot analysed. 2.5 DCST The word ' pollutants' makes us think of acid rain, sulphur dioxide and nitrous oxide, present in the outdoor environment as a result of gas pollution. In museums, heritage houses and our homes events involving these pollutants rarely occur. There is , however, a major problem in museums and houses caused by particulate pollution - dust. D ust contains all sorts of airborne particles that settle out and are deposited on or adjacent to heritage objects. Uepend -ing on where the building is the dust can contain any of the following: human e pithelial cells (skin debris) , textile fi bre fragments. starch grains, fungal conidia and spores, pollen grains, carbon soot and inorganic crystal of all kinds. ] n a museum that is visited by thousands or people, the dust will contain many skin epithelial cells; ir there are wall -to wall 12 Herilage Ealers carpets, there will be lots of rug textile fibres; if it is an agricultural region, there will be fungal conidia, starch grains, etc. Some particulate pollutants are removed by air filters but others gain access to buildings with people and through open doors, windows, docking bays, etc. Oust may be a source of nutrients for some insects or fungi and it may form a microenvironment on surfaces as it prevents normal air flow over them and the large surface areas of the small dust particles will adsorb moisture. Both these factors will improve the environment for pests. The dust, per se, does not cause a problem for heritage objects but the organic material within it is fodder for pests. Some infestations of insects and fungi on objects can be solely supported by organic materials in the dust. For further information on dust, see Thomson ( 1986). 2.6 AlH ClHCULATI ON Air circulation, of course, influences the moisture content on the surface of and within materials. If we want to dry things rapidly, we use fans , as well as heat. '\Iovement of air also prevents accumu lation of dust, and the fungal conidia con-tained in it, on surfaces. The application of air circulation to prevention of insect and fungal pests in heritage collections is in its infancy. Sakomoto el aL ( 1995) reported on tests con-ducted in storage facilities and in chambers with a controlled, weak air flow. Use of the air flow resulted in restrained fungal growth. Arai ( 1995) used on cabinets a type of louvre that encou raged air circulation and was able to show how this reduced fungal activity. Both cases must involve the elimina-tion of microenvironments of high moisture content and/or the simple removal of conidia . These are further examples of the im portance of microenvironments. HEFEHENCES Arai, II. 1995. Personal communication Brill, T.B. 1980. Light, its interaction uJithArt andAntiquities. Plenum Press, ~ew York, London. Carlene, P. W. 1944. T he moisture relation of textiles, a sun'ey of the literature. Joumal of the Society of Dyers and C%urists, 60:232-257. D'Arc)" R.L. and LA. \·Vatt. 1981. \V ater yapor sorption isotherms on macromolecular substrates. Tn lFater Activity: Influences on Food Quality, Eds R.L. Rockland and G.F. Stewart. 1981. Academic Press, ~ew York, pp 111-142. florian, ;\ l -L.E. 1986. The freezing process - effects on insects and artifact materials. Leather Comervation News, 3( I): 1-13, 17. lloadley, H..I3. 1980. Understanding IFood. The Taunton Press, ~ew­ton, Connecticut. Kapsalis, J.G. 198\. ;\Ioisture sorption hysteresis. I n lYater Activity: influences 011 Food QuaLity, E.ds H.L. Hockland and G.F. Stewart. 1981. Academic P ress, Kew York, ppI44- 165. Kapsalis, J.G. 1987. Influences of hysteresis and temperature on mois-ture sorption isotherms. In IFaterActivity: Theory and Application to Food, Eds L.13. Rockland and L.R. l3euchat. ;\Iarcel Dekker Inc., ~ew York , pp171-213 La Fontaine, H. 1984. SiLica GeL. e.c.1. Tech. Bull. Ko. 10. La Fontaine, R.H. and S. ;\Iichalski. 1984. The control of relative humidity: recent dc\·elopments. Preprints, rCO,ll Committee for Conservation, Copenhagen, 2:84.17.33-57. .\Iichalski, S. 1987. Damage to museum objects by visible radiation (light) and ultra\'iolet radiation (uv) . I n Lighting in Museums, GaLLeries, and Historic H ouses. T he .\Iuseums Association, London , pp3-16. .\Iichalski, S. 1989. A light damaged slide rule. Proceedings oflhe 14th AnlluaL llC-CG Conference, p22 .\Iichalski, S. 1994. Relative humidity in museums, galleries and archives: specification and control. I n Bugs, It'/oLd and Rol r1: A IVorkshop on Control oj [-Jumidity for H ealth, Artifacts, and BuiLdings. ;'\ationallnstitute of l3uilding Sciences, \Vashington , pp51-62. Panshin, A.J. and C. de Zeeuw. 1970. Textbook oflrood TechnoLogy, Vol. 1. 5rd Edition . .\lcGra w -IJill Book Company, ~ew York. Hockland, R.L. and G.F. Stewart. 1981. IVater Activity: Influences on Food Quality. Academic Press, New York. Sakamoto, K. , K Kurozumi and T Kcnjo. 1995. A simple method for temporary conservation of art objects: effect of air flow for prevent-ing fungal grow th. Jrd rntemational COliference 011 Biodeterioration of CuLturaL Property, 4-7 JuLy, Bangkok, Thailand. Stolo\\" N. 1966. COlllroLLed Environmentsfor IVorks of Art in Transit. Butterworths, London. T homson, G. 1986. The Museum Environment. 2nd E.dition. Buttcrworths, London. T roller, J .A. and J.II.B. Christian. 1978. lFater Activity and Food. Academic Press. Xew York. Watt, J.c. 1979. Water vapor sorption hysteresis in swelling substrates. In Physics ofJ)1alerials, Eds D.\·V.lloriand, L.'\1. Clarebrough and A.J.W. ;\Ioore. Commonwealth Assoc. and Industrial Research Organization, Australia. Watt, J.c. 1980. Sorption of water \'apor by keratin. JournaL Nlacromoi. Sci.-Rev. Macromoi. Chern., C 18(2):169-245. Weintraub, S. 1981. Studies in the beha\'iour of RH within an exhibi-tion casco Part 1. ;\ Ieasuring the effectiveness of sorbents for use in an enclosed showcase. Preprinls, iCONI Committee for Conserva-tion, Ottawa, 81.18.4. 1J 3 Classification, N aIDing and Diagnostic Features of Common Insect Heritage Eaters 3.1 TH E GRO UPlt\ G OF AXIMALS The animal kingdom is divided into 13 major groups, called phyla. The animals in each phy lum have common character-istics, for example, all animals with an internal skeleton are in the phylwn Chordata and all single-celled animals are in the phylum Protozoa. A phylum is subdivided into smaller groups of animals that have similar structural features and these groups are subdi-vided in turn into still smaller groups of animals until the individual species is reached. The sequence of groups is as follows: phy lwn, subphylum, class, subclass, division, order, suborder, superfamily, family, genus and, finally, the individual species. 3.2 T HE PHYLUM AIlT HROPODA fnsects are included in the phylum Arthropoda. The arthro-pods include not only insects but other animals, e.g. spiders, crabs, lobsters, centipedes, etc. T he animals in this large group have the following mor-phological features in common: • a segmented body • segmented, jointed , paired appendages • bilateral symmetry • chitinous exoskeleton . 3.3 CLASS INS ECTA T here are many classes in the phylum Arthropoda. T he insects are all grouped in the class lnsecta (or Hexapoda). T he exist-ence of two alternative names for the class demonstrates how the naming of organisms is an ongoing discipline and new names are being introduced continuously to give clar-ity and to utilize ne\-v information about the relatives of insects. Insecta (Hexa poda) Pigure 3.1 illustrates t he parts of an adult beetle. Adult insects have a distinct head, thorax and abdomen. Three pairs of jointed appendages, or legs, developed on t hree body segmen ts form the thorax. T he head segments, bear a pair of antennules, antennae, mandibles (jaws), maxillae and the labium. The abdomen may have up to 11 segments. antenna ocellus (simple eye) \ ! pronolum ~:L /C.J..::-r---- head scutellum __ ---:::<,r--elylra ___ =:::::;~~--r apices prosiernum hypomeron anlennal club mesosternum femur __ ~_ libia_ ._._ head , , setal tuft ~J / tarsus/ elytran femur basal anlennal segment I I cmal plale Irochanter lateral impressed line \ visible abdominal Slernile Figure 3.1. T op, dorsal view if a carpet beetle, Anthrenus fuscus. BOllom . , ventral view of a tzide beetle Dermestes sp. (peacock, 199J, In:th permission). The typical lateral compound eyes are present in adults and nymphs but absent in the larvae. Simple eyes. ocelli , may be found on adults: one medium and two laterally placed dorsal ocelli. 14 Hen:tage Eaters 3.4 CLASSIFI CATION OR NA~II NG OF INSECTS There are probably millions of insect species. The task of naming or classifying them is as enormous as their numbers. The information presented here is, basically, the classification of the heritc'l.ge-eating insects discussed in this book. The value of knowing thei r classification is as a means of COiTUllwlication so that it is clear exactly what insect is beingd_iscussed. Italsa makes possible logical groupings of insects with similar characteristics, at the same time enabling specific differences to be shown. Many insects do not have a common name or the same common name may be given to several different insects. These problems are overcome by using the Linnaean system of binomial nomenclature, which gives every insect two Latin names: genus and species. The genus is a generic name for related species, and the species name is that of a group of individuals that interbreed. These two Latin namesarealways used together and are italicized, as in this book. The combination of a generic and a specific name gives a ullique name for each kind of insect. Examples are shown below with : Blallaon:entalis, the oriental cockroach: Blallella germanica, the German cockroach; and Tineala bisselliella, the common clothes moth. Blatta, Blauella and Tilleala are generic names, and orientahs, germanica and bisselhella are species names. The two insects with the common name of cockroach are not of the same genus and do not interbreed. In textbooks the first time the insect is mentioned both the generic and species names are given in full , but in subsequellt references the generic name may be abbreviated to the first letter, e.g. T bisselliella. Sometimes the name of the scientist who described the insect is included after the species name, e.g. Blalla oriel/talis Linnaeus, Tineala bisselliella (I [ummel). The full scientific names of the common heritage eaters are listed in 3.6. T he full classifications of the cockroach and common webbing clothes moth are given as exam ples, to show all the subdivisions: Class Insecta Subclass Apter,ygota - wingless Ol'dcl' Th ysa lllll'a - silverfish , firebrats Subclass Pterygota - winged insects Division Exopterygota: simple, incomplete meta,norphosis, wings develop externally Ol'del" Isopte l'a - termites Ol'del' Psocoptel'a - psocids, booklice Ol'der Blattodea - cockroaches Suborder - D ictyoptera Superfamily - Blattoidea Family - Blattidea Genus - Blatta Species - Blatta arientalis Linnaeus Oriental cockroach '1.5 Superfamily - Blaberoidea Family - Bl attellidae Genus - Blattella Species - Blauella germanica (Linnaeus) German cockroach Division Endopterygota: complete metamorphosis, wings develop internally O l'del' Co leo pter'a - beetles Or'dcl' Dipte ra - flies O,'de,' Hym e nople l'a - ants Ol'der Lcpidoptcr'a - moths Suborder - Ditrysia Superfamily - T ineoidea Family - T ineidae Genus - Tineola Species - Tineala bisseLLieLLa (Hummel) common clothes moth CLASS IFICATION BASED ON ~ I ETMIOI\PHOS I S AND A 'JATO~ IY The classification of insects is based on anatomical features of the adult and type of development of egg to adult. I n the groups of insects listed in 3.6 there are two types of development or metamorphosis: 3.5.1 l\ le lamor'phosis IYCO\lPU~TE \1£'1'4 \lORPHOSIS In incomplete metamorphosis the egg develops into a minute immature stage that looks li ke a small adult. There are many moults and each new nymph looks more like the adult. "V hen the nymph changes into the sexually mature adult stage it undergoes only slight morphological changes, usually only the development of reproductive organs. T he life cycle of a cockcroach (Figure 3.2) illustrates incomplete metamorphosis. CO lJPLET~,: lfer4IIORPHOSIS In complete metamorphosis the egg hatches into an immature form , a larva, which does not resemble the adul t form . The larva goes through many moults: each time the result is a larger larva. I n its last moult th e larva body is completely reconstructed into a pupa, an im m ature adult in a pupal case, and from th e pupal case a mature adult emerges . The life cycle of a moth (Figure 3.3) illustrates complete meta -morphosis. 3.5.2 Anatomi ca l fealul'cs T he class Insecta is subdivided into 29 orders; only the eight orders that include the insects discussed in this book are listed in Box 3.1 . Classijica!.ioll, naming and diagnoslicJeatures oj comrnon insect heritage ealers 15 ~ ~  egg • [ ~~~~211 \u 'v~~~ ' I - . / -- ---- -,. : . _ . . pupa _: ", larvae Fig ure 3.2. The life c)'cle oj a cockroach, dluslrating incomplete m etamorphosis. The egg hatches I:nlo a nymph, which resembles the adult bUl is smaller and sexuall), immature. The nymph goes through a series oj moults, each time increasing in si=e and resembling more the adultJorm. During the last moull, a sexually mature male or Jemale adult isJormed, which la)'s or fertili=es the eggs to repeatlhe c)'c1e (after BenneLl et al.. 1997). Figure 3] T he life cycle cif a moth, illustrating complete metamorphosis. The egg hatches into a worm.-like larva. The larva moults several times; each time it is larger bUl retains its larvalform. In itsfinal m.Gult the larvaJorms a pupa, which may be a partially orJully Jormed, donnanl adult. l'Vhell the pupa breaks dormancy, it goes through pupation and a sexually mature adult emerges to repeatlhe cycle (after Bennett et ai., 1997). 16 Heritage Ealers 3.6 THE COMPLETE SCI El'lTI FIC ;"''\'1) CO~I~ I ON SMIES OF INSECT HERITAGE EATERS CITED CLASS INSECT A: SUBCLASSAPTERYGOT/J - wingless insects Order T h)'sa nul'a - silverfish, firebrats Family Lepismatidae Aerote/sa collaris (Fabricius) - large silverfish Clenolepisma lineala pififera (L ucas) (= quadriseriata Packard) - fourlined silverfish Clenolepisma longicaudataEscherich (=urbana Slabaugh) - grey silverfish, giant silverfish Lepisma saccharina Linnaeus - common silverfish, silvermoth Lepisnwdes inquilinus ~ewman - fire brat Therrnobia domeslica (Packard) - fire brat SFBCLASS PTER YGOT/J - winged insects DIVISIOK EXOPTER YGOTA - simple, incomplete meta-morphosis, wings develop externally Orde r" I sop te r'a - termites Family Hodotermitidiae Zoolermopsis spp. - dampwood termites Family Kalotermitidae Calcaritennes spp, - powderpost termites CryplOlermes spp, - powder post termites Kalolermes spp. - dry\vood termites Incisitermes spp. - dry-wood termites LVeotermes spp, - dampwood termites Paraneotermes spp. - dampwood termites Family Rhinotermitidae Reticult:lermes spp. - subterranean termites O,'de,' Psocoptc l"a - psocids, book lice Family L iposcelidae LI:posceLis divinalorius (:\1 uller) - book louse OI'dc l" Bla ttodea - cockroaches Family Blattides Blalla orientalis Linnaeus - common oriental cockroach Pen:planeta americana (L innaeus) - American sh ip cock roach Periplaneta auslralasiae (Fabricius) - Australian cock-roach Family Rlattellidae Blauella germalll:ca (Linnaeus) - German cockroach O IVISIO:\ E:\OOPTER YGOTA -com plete metamorphosis, wings develop internally Orde l' Coleoptera - beetles Family Bostrichidea J-Jelerobosllychus aequalis ( \Yaterhouse) Lyctus brunneus (Stephens) - brown powderpost beetle LyclUs planicollis LeConte - southern lyctus beetle, true powderpost beetle Family Anobiidae Anobium pUIlClalum (De Geer) - common furniture beetle, false powder post beetle, furniturewoodworm Hylolrupes bajulus (Linnaeus) - old house beetle Lasioderma serricorne (Fabricius) - cigarette beetle Slegobium paniceum (Linnaeus) - drugstore beetle, bread beetle, biscuit beetle Xeslobium rufovillosum (De Geer) - deathwatch beetle Family Dermestidae Anlhrenusjlavipes LeConte - furniture carpet beetle Anlhrenllsfuscus Olivie - furniture carpet beetle Anthrenus museorum (Linnaeus) - museum beetle Antlzrenus scrophuLarzae (Linnaeus) -common carpet beetle Anlhrenus verbasci (L innaeus) - varied carpet beetle A llagenus brnnneus Faldermann - two-spotted carpet beetle Allagellus megatoma (Fabrici us) - black carpet beetle Allagenus pellio (Linnaeus) - fur beetle Aaagenus piceus (Olivier) - black carpet beetle Allagellus unicolor (Brahm) - black carpet beetle Dermestes aler De Geer - black larder beetle Dermesles lardarius Linnaeus - larder or bacon beetle D ermesles maculalUS D e Geer - h ide beetle D ermesles vulpl:nus Fabricius - leather beetle IVlegatoma undata Linnaeus - carpet beetle Reesa vespulae (Milliron) - musewn nuisance, carpet beetle Thylodrias contraclus Motschulsky - odd beetle Trogoderma incfusum LeConte (= vericolor [Creutz,])-large cabinet beetle Trogodenna granarium Everts - khapra beetle Trogoderma ornalum (Say) (= tarsalis Nlelsheimer) -cabinet beetle Trogoderma variabile Ballion (= parabile Beal) - ware house beetle, hide beetle Family T enebrionidae Tenebrio molitor (Linnaeus) - yellow mealworm, grain beetle Tenebrio obscurus (Fabrici us) - dark mealworm Trilobium caslaneum (Herbst) - grain beetle Tlilobiumconjusum Jacquelin du Val -confused flour beetle Family Ptinidea Gibbiwnpsylloides (de Czenpinski) - hump spider beetle, shiny spider beetle Me=.ium americallwn (Laporte) - American spider beetle Nitpus hololeucus (Falderman) - golden spider beetle Plinus clavipes P anzer (= hirtellus Sturm) - brown spider beetle Plinusfur (Linnaeus) - white-marked spider beetle Pll:nus ocellus Brown (= lectus [BoieldieuJ) - Australian spider beetle Plinus villiger Reitter - hai ry spider beetle Family Odemeridae Nacerda melanura (Linnaeus) - w harf borer Ol"der Diptel"o) - nies Family;Vluscidae Nfusca domeslica Linnaeus - common house fly Ol"del" Hyme noptera - ants Ol"de ," Le pidoptera - moths Family Tineidae Tinea pallescentella (Stainton) - large pale clothes moth Tinea pellionella (L innaeus) - case-making clothes moth Tineola bisselliella (l iummel) - webbing clothes moth, common clothes moth Trichophaga lapel::ella (Linnaeus) - tapestry moth Family Oecophoridae Endrosis sarr:ilrella (l ,innaeus) - white-shouJdered house moth Epheslia caul£lla (\ Valker) - almond mou1, dried currant moth Ilofmannophila pseudosprelella (Stainton) - brown house moth Classification.. narning and d iag noslicJeatures oj com mon. insect herilage ealers BOX If DIAGNOSTI C FEA T URES OF A D UL T ISSECT HEHITAGE EA T EHS OJ'dCl' Thys3nuI'a - silve rfi sh, firehrats In complete m e tamorphosis , nymphs like small adults , all stages cause damage with chew-ing mou thparts, flattened fi sh-shaped , less than I Dmm long, long antennae directed forward , three tail -like cerci of equal lengths. Ol'de l' Isopte r'a - termi tes Incomplete metamorphosis , so-cial insects. workers and soldie rs wingless and light-coloured , swarmers dark-bodied with four equal length wings. Ko waist be-tween abdomen and tho rax , chewing mouthpa r ts , workers cause damage. Orde r' Psocopte l'a - psocids, book lice I ncomplete metamorphosis , nymphs like small adults , all stages cause damage. Small, 1-21nm, soft-bodied, antennae long and slender. light-coloured, usu-ally wingless. chewing mouth parts. Orde r' Blattodea - cockroaches I ncomplete metamorphosis , nymphs like small adults, all stages cause damage. Flattened dorsov-e ntrally, ch ewing mouthparts, prothorax large and shield-like, usually four wings, when present the fron t pair is thickened and leathery and th e back pair is m embranous and folds beneath the front wings, legs adapted for running. Ol'dc r' Coleoptcra - beetles Complete metamorphosis. Adults: hard shell-like front wings (elytra) which meet, when in rest, on a straight line down the back, hind wings fold under front wings, adults may or may not feed. Larvae : vary. may be grub- li ke to ca terpillar -li ke, three pa irs of ar -t icula ted thorac ic legs. I lead , hard, sci e roti zed ca psule; ocell i, no com pound eyes. ~ louth pa rts opposa ble ma ndibles, larvae usu-ally cause damage . Ol'de r Diptc r'a - fli es Com plete metamorphosis . Adults: Two pairs of wings, front pair membranous, ba ck pair forming knobs called halte rs, mouthparts for piercing, sucking or sponging. ~ .1ay damage herit-age materials by soiling with fae -cal material (fly spots), carpet bee-tle larvae may be harboured in dead adult's abdomen. Larvae: maggots, grub-like, live on moist dead organic material. Or'de l' Hym e noptel'a - ants Complete metamorphosis. Adults: Social insects, different castes, worker ants are wingless, reproductive adults have four wings. ~ louth parts adapted for chewing or lapping, damage caused by adults tunnelling in wood or scraping organic mate-rial from surfaces. Larvae: vary, may be grub-like wi thout legs, may have mandi-bles, adults feed larvae. Ol'del" Lep idoptera - moths Com plete metamorphosis Adults: four wings, m embranous and covered wi th overla ppi ng scales. Adults have mouthparts adapted to sucking, do not cause damage. Larvae: var )" grub~ like to cater-pillar-like, three pairs of pro legs, some with hooked crochets in cir-cles or rows on the pad of each prdeg. H ead, dark, sclero tized capsule, soft body. ~ louthparts with opposable toothed mandi-ble, silk spinnerets present, cause damage. l llustrations by Lori Graves 17 18 H eritage Ealers i ~ ~ MITES i wif'l8S ",til devdopc:d i front wing' shell- like BEETLES-WEEVILS-BORERS-MEAL WORMS I p air .,dogs ~ '-7~ fLIES , wings ... ilh solei ~ ~ MOTHS frOfll ,..ings nor shell ·like .... ings ... i,houl scalCi COCKROACHES I 3 body (tgi o ns ,.,. i ngs reduced or abHnl ~,  - ~ ~l/ ' ( " -.•.• 1. · '" . I " SILVERFI SH i anann) 4·7 segm ented lUSUS ' ·5 scgmcnu:d ~ (\ ~ I " ' irhour j long 11ih morc (han 7 scgmef\lu tarsus \. ) segmented PSOC )DS ~------""irh narrow wain ANTS COCKROACHES Figure JA. A key La common insecllypes (ScaN, 1959, U.S.D.I-/.E.l fT). Figure 3.4 shows a key to common insect types (Scott, 1959). ,I EFE fl E:\CES Bennett, G.\\ " J.:\1. Owens and H. \1. Corrigan. \997. Trumans Scien-tific Guide to Pest Control Operations, 5th edition. Ad\anstar Com-munications Inc., Clc\'eland , Ohio. Gullan, PJ. and P.S.Cranston. 1994. 'nle Insecl~;An OutLi"eofEntomology. Chapman and Ii all. London, ~ew York. Peacock, E.B. 1993. Adults and L arvae of Hide, Larder and Carpel Beetles and (heir Relatives (Co[eoptera; Dermesridae) and of Derodofltid Beetles (Coleoptera.' Derodonlidae). Handbooks ror the [delll ification or Br itish Insects, Vo1.5, Part .3,. Boyal Elllomologi -cal Society of London, London. Scott, II.G. 1959. lIousehold and Stored-Food Insects of Public Health Importance and their ControL. U.S. Department or Health, Educa-lion and Welfare, Atlanta , Georgia. 19 4 Exoskeleton and Moulting 4.1 INTHODUCT IOX The outer surface ofinsecl nyrnphsor larvae, pupae and adul ts iscalled the exoskeleton or integument. For th e insect, the role of the exoskeleton is fundamental: it is the basis for their survival and evolutionary success. It acts as the skin, defines the insect and, like a skeleton, gives support to its soft body and muscles. The exoskeleton prevents body water and oxygen loss , a ids in body temperature control and protects the insect body from parasites, micro-organisms and ultraviolet light. It must be soft and flexible to allow for movcmentand extensible to permit growth. I n some parts , it must be thin to allow oxygen diffusion to individual cells and, in others. hard and horny for mandib les and claws. The exoskeleton is the site of many sensory organs involved in detecting water. chemicals and movement, and can c"en be used as a food source for its own and other species' larvae. Because many insect eradication methods use chemicals, gases or abrasive and adsorbent powders, whose actions are influenced by the exoskeleton, relevant information about its structure is presented here. D espite the fa ct that it is usually the larvae that are the heritage caters, because we rarely sce the larvae until after the fact , we concentrate 011 the adults. \lost of the information in the literature, reviewed here, is about adults but it is applicable- to other life stages. 4.2 STHUCT UHE OF TH E CUT ICLE The exoskeleton is made up of three layers (Pigure 4.1 ): an outer, non~cellular cUlicle (procllticleand epicuticle) of unique chemicals; an underlying layer of cells called the epidermis that secretes the chemicals of the cuticle; and the non ~cellular basal membrane below the epidermis. The epidermis is a layer of cells that secretes the chemicals used for moulting of the cuticle and also supplies all the chemicals used in forming the different layers of the new cuticle. The epidermis cells do not divide but they grow in size with larval growth. The cuticle, the non-cellular outer layers of the exoskel-eton, is our main concern. There are three main regions in the cuticle: the endoculicle, exocuticle and epl:culicle. The endocuticle is the region, accounting for about two-thirds of the cuticle, adjacent to the epidermis. I t is made up of chitin-protein polymers and is responsible for the extensibil~ ity and flexibility of the exoskeleton . =~-==o=",.c~;b~epic1Jticl e exoculic1e procuticle epidermis t':£::C:;;:~~:'L:;;;~~~U~~J1-besement membrane gland Fig ure 4.1. General Slruclure of insect cuticle: the enlargem enl above lhe main diag ram shows delails of the epicuticle (Gul/an and Cranston, 1994. willi permission) The exocuticle is the dark, hard , outer one-third of the cuticle. It is made up of chitin and quinone-tanned pro-teins. It provides rigidity for the hard parts of the head and legs. 20 Heritage Eaters The epicuLicic is the thin surface on the exocuticle, consist-ing of a wax layer about O.I - 3.0Jlm in thickness or a varnish -like cement. Jt is this extremely thin wax layer that is so critical in preventing body water loss. The trachea are im'aginations of the epidermis, so their lining is continuous with the exocuticle. The chemistry of the tracheal cuticle resembles the exocuticJe, but with a few exceptions: there is no epicuticle wax or cement present and in the finer branches, the tracheole, chitin is absent. (See chapter 5 on the tracheal system). For further information on cuticle structure, see Andersen (1979), Gullan and Cranston ( 1994). Locke (1974) and \Vigglesworth ( 1984). 4.3 TH E C HDII CALS IN nlE CUTICLE The chemicals of the layers each playa specific role in the protective nature of the cuticle. 4.3.1 Chitin-pro te in polymers Chitin-protein polymers are in the endocuticle and exocuticle, but not in the epicuticle. Chitin is a colourless polymer which is insoluble in water, dilute acid or alkali, alcohols and all organic solvents. The chitin polymer is in the form of submicro-scopic crystallites aligned to form larger rodlets, which align to form larger microfibrils, and these fonn fiblils that in tum foml lamellae. Protei.n bi.nds all the levels together. In the chitin-protein complex, d1itin gives strength and protein acts as a plasticizer. It is this dense alignment of chitin crystals that protects the chitin against solubilization. The only thing in nature thatcan dissolve it is the complex mixture of enzymes (including chitinase. glucanase and protease) found in the moulting fluid and also produced by a few insect-eating bacteria and fungi. 4.3.2 Sclel'o liza lion Theexocuticle contains chitin-protein polymers and a protein component, which have been converted to a horn -like mate-rial called sclerotin in a hardening process is called sclerotization. The proteins are tanned, like leather, by phe-nolic quinone tanning agents, which create one of the strong-est protein cross-linkage bonds known. If t.he exocuticle is sclerotinized it cannot be digested even by the moulting fluid and is left behind as the exuvium or moult. Tyrosine is the main protein and its presence contributes to the amber colour, along with melanin. lVlelanin, the same brown pigment found in our hair, is commonly present in the insect cuticle and adds a black or brown colouLIt is usually involved in the formation of colourful and metallic physical colours. :\1elanin protects the soft body of the insect from ultraviolet damage and from micro-organism attack. :\1elanin also inhibits the enzyme mixture that digests chitin. For further information on sclerotization, see Hicketts and Sugumaran (1994) and \Vigglesworth (1985). 4.3.3 Epi cut icle " ax a nd ceme nt There are minute tubes throughout the cuticle that bring lipids and proteins to the surface of the exocuticle. The lipoproteins and the crystalline wax surface, which form the epicuticle, cover the exocuticle and make it waterproof. The waxes are chemically different in different insect species (Gilby, 1980). In some insects there is a varnish-like substance over the epicuticle called cement. Shellac is a commercial product made from thecementofthe lac scale insect Kerria lacca and is used like a varnish to flllish wood surfaces on furniture. The waxes vary from the soft, greasy material on the cockroach to the hard, crystalline wax found on 7'enebrio larvae. The chemical composition of the waxes va:ies with differ-ent species. The melting points, or transition temperatures, of the waxes also vary. \V hen the waxes melt, the cuticle appears to lose its water impermeability and this is expressed in the different heat tolerances of different species. For further information on cuticle chemicals, see Andersen ( 1979), Hackman ( 1978) and Wigglesworth (1984). 4.4 ~IECHANICAL Pl\OPEIlTIES OF THE CUTI CLE \Yhen the cuticle is first laid down by the epidermis. it is soft and white but the exocuticle usually quickly becomes dark and hard through sclerotization. I t remains soft and white in some larvae and in some adult insects, i.e. booklice or subter-ranean termites. but in most adult insects the exocuticle becomes dark and hard. Lepidoptera (moths and butterflies) and Coleoptera larvae have a soft plastic cuticle throughout the instars (the larval or nymph stage between the moults) with great extension ability to accommodate larval growth. The cuticle of adult Coleoptera is brittle and hard as a result of sclerotization: plasticity and increase in size is limited to brief periods before hardening, immediately after pupation . There is evidence that the cuticle p lasticity can be altered by a shift in the p i-i of the diet: when acidic it is hard and when alkalinesoft(Andersen, 1979). In addition, there are regionsof the whole cuticle that are more plastic than others: abdominal intersegmental membranes of female termites can extend 10-fold to accommodate egg production. ] n the exuvium of the common carpet beetle, intersegmental bands of hard, brown, sclerotized cuticle are obvious between plastic, white segments. For further information on mechanical properties of cuti-cle, see Locke (1974). 4.5 II'AT EH PEH~I EAB ILlTY OF T il E CUTICLE The ability to adsorb water vapour through the cuticle is dependent on the insect species, its stage and s ize, the structure of the epicuticle, nutritional state, environmental tempera-ture and relative humidity (RH ). To general ize is impossible, but active water uptake does occur through the cuticle, which does not have an epicutical sur face wax lipid / protein layer. Brown, ridged , sclerotized exoskeletons usually have an epicuticle but white, soft nonsclerotized exoskeletons of lar-vae, booklice, white termites and ants are without it. Subter-ranean termites and drywood termites maintain their body water by adsorption of water vapour through the exoskeleton from the humid a ir in the galleries of the wood in which they live. Strangely, flrebrat and meal worm larvae can absorb moisture through the anal opening. Exoskeleton and moulting 21 Table 4.1. R elalive humidilies (RH) al u:hich insecls have been slzoum to adsorb water vapour/rom the air Insect species Cigarette beetle larva - Lasioderma serricorne Firebrat - Thermobia domestica Prepupa of flea Booklice - Uposce/is divinatorius Yellow mealworm larva T enebrio mo/itor Cockroach nymph Psoc id booklice RH (%) 43 45 50 60 90 82 53-58 At We HHs shown in Table 4.1, the insects specified, partially hydrated, have been shown to adsorb water vapour from the air, without eating and drinking, causing an increase in body weight. For further information on cuticle water permeability, see Ebeling (19 74) and Gilby ( 1980). 4.6 I'U LXERAB ILITY OF T HE E PI CUTICLE TO TE\IP ERATURE Kno,,·ing the structure of the cuticle allows us to pinpoint its weakest or most vulnerable part. and helps us to design erad ica tion methods based on this weakness. The presence of the eA'tremely thin wax layer of the epicuticle makes the insects vulnerable to abrasion, fat-soluble chemicals and heat. Abrasive dusts of borax or diatom.aceous earth are used as insecticides because they remove the extremely delicate epicutic\e and cause lethal dehydration (Ebeling, 1971, 1974). Soaps are also used in insecticides because they dissolve t he wax of -the epicuticle and the insect dies of dehydration. Surfactants and wetting agents are used in insecticidal prepa-rations to wet this wax, so the toxic insecticides can be more easily absorbed into the body of the insect. Heat treatments for eradication of insect pests arealso used. Temperatures of 40-60oC have been shown to cause rapid loss of body water , leading to death, in a variety of insects. Death has been attributed to dehydration because the heat melts the wax in the epicuticle. The waxes of different insect species have different melting temperatures. Cock-roaches show a rapid loss of body weight due to water loss auributed to the transformation of the epicuticle wax at 30°C. Figure 4.2 shows how three types of grain beetle demon-strated a dramatic increase in weight loss due to water loss at the temperature that disrupted the molecular orientation in the lipid layer of the epicuticle. Gilby ( 1 980) discussed the problem of interpreting the litera-ture with reference to the role of temperature transition and transpiration. As with the literature on lethal freezing tempera-tures (see chapter 12). Gilby (1980) wrote of the literature on transpiration, 'For a rigorous analysis of experimental results it is necessary to know the physical properties of the insect .. in addition to environmental parameters'. He suggested that the evidence in the literature shows no abrupt change, as at a critical temperature, or melting or crystalline change of the waxes, but a gradual increase in permeability with tempera-ture. Temperature increase may have many possible results. which must be considered: increase in metabolic activity. increase in rateof external respiration. heat damage of cellular \ ;; ~ 7 20 30 so 60 70 Tempera!'! re (GC) Figure 4.2. Abrupl rise in rale oju,·eiglu loss due to u·aler loss for three species oj lenebrionid beetles al crilicallemperature points. 0 Eleodes armata; • Centrioptera muricata; ... Cryptoglossa ,'errucosa (JromAhearn, 1970). components, increase in vapour pressureof water. etc. (!\ Jachin and Lampert, 1989). The presence of lipids has been demonstrated byapplica-tion of solvents and abrasion, but the molecular architecture and the theory of its function are not clear, according to :\Iachin and Lampert (1989). These authors showed from their research that permeability increases occurred between 35 and 40°C and were irreversible in pieces of excised cuticle and that the permeability increased as the temperature rose, with no distinct transition. So much for the melting wax theory. 4.7 ~ I OULT li\G O R ECDYS IS The cuticle gives the larvae and nymphs its many protective features but, because it cannot expand or grow once it is formed, it has to be shed periodically and a larger new cuticle formed to accommodate growth. The shedding of the cuticle is called moulting. \loulting is a complex process il1\'olving hormonal. behav-ioural, epidermal and cuticular changes. The end result is the shedding of the old cuticle or exuvium. A new cuticle is laid down by the epidermal cells. The hormones and their concentrations during the life of a larva are shown in Figure 8.1 (in chapter 8). A hormone called the juvenile hormone (JI-I) is needed for the larva to go through the necessary instar growth . High titres of JH inhibit the expression of adult features, so they are associ-ated with a larval-larval moult; low titres of JH cause a larval-pupal moult. Follo"'ing the last instar moult, there is a dramatic reduction in JH , which insures that the moult goes into a pupa. 22 H eritage Eaters Dmingmoulting, an increase in ecdysteroid hormonestimu-lates the epidermis, which leads to the formation of a new cuticle. J H is used as a form of insect pest control , to prevent adult formation in insec t populations. It does not kill the larvae immediately, but the metabolic imbalance will eventually do so. The cuticle of most larvae remains soft a nd flexible and may not have a sci erotized or waxy e picutica l. If present, a sclerotized exocu ticle is usually confined to the head or dorsal segment pla tes . A differentiated exocuticle and endocuticle appear when the pupa is clothed (pharate) in the larval-pupal moult. This last instar is often a wandering stage, during which the larva wanders away from its feeding site to find a suitable place to pupate. The sequential steps in the process of moulting a re : Enzymatic digest ion of the endocuticle, between the epi-dermal cells and exocuticle, by the moulting nuid; 2 Absorption of the dissolved endocuticle; Formation of a new cuticle by the epidermal cells; 4 Rupturing and removal of the insoluble exocuticle and epicuticle (the moult or exuvium); Expansion of the new instar and of the new cuticle; The hardening and sclerotization of parts of the exocu ticle. The exuvium is composed of the sci erotized exocuticle and epicu ticle . These structures contain lip ids that a re free, not bound to the protein -chitin complex, and. if the ex uvium is eaten by a larva itcan utilize the lipids for nutrition. Sometimes these lipids can also beabsorbed back into the body of the larva if it is under stress from lack of food. IlEFEIl ENCES Ahearn, G.A. 1970. The control o f water loss in desert tenebrionid beetles. The Journal of E2perimenlal Biology, 52:573596, Andersen, 5.0. 1979. Biochemistry of insect cuticle. /Innllal Review of Enlomology, 24:29- 62. Ebeling, W. 1971. Sorpti\'e dusts for pest control. Annual Review of Enlomology, 16: 125- \58. E.beling, W. 1974. Permeability of insect cuticle. I n The PhysioLogy of insecta, \ ' 01. 6, Ed. :\l orris Hockstein. Academic Press, New York , pp271-345. Gilby, A.H. 1980, Transpiration, temperature and lipids ill insect cut icle. Advances in Insect Physiology, 15: \-33. Gullan , P.J . and P.S. Cranston. 1994. Theinsects:An OutlineofEntomol-ogy. Chapman and Ii all , London, Kew York. Il ackman , H. 1-1 . 1974. Chemistry of the insect cuticle. In The Physiol-ogyofinsecla, \ '01. 6 , Ed. :\Iorris B.ockstein. Academic Press, :\ew York, pp2IS- 270. Locke, :'II. 1974. The structure and format ion of the integument in insects. In The Physiologyoflnsecla, \'01. 6, Ed. :'Ilorris Hockstein. Academic Press, Kew York, ppI23- 215. :'Ilachin, J. and G J .Lampert. 1989. Energetics of water diffusion through the cuticular water barrier of Periplaneta: the effect of tempera -ture, revisited. Journal of Insect Physiology, 35(5):437- 445. Hicketts , D. and ;\1. Sugumaran. 199'~. 1.2 - D ehydro- ~ - B ­alanyldopa mineas a new intermediate in insectcuticularsclerotization. The Journal of BiologicaL Chemistry, 269(35):22217- 22221 Wigglesworth , \ T.13. 1984. l mecl Physiology, 8th edition. Chapman and I lall, London , :\ew York, pl91. Wigglesworth. v.s. 1985. Sclerotin and lipid in the waterproofing of the insect cuticle. Tissue and Cell, 17(2):227-248. 2J 5 The Tracheal System 5.1 STIl UCTUIlE OF TRACHEAL SYSTDI The function of the tracheal system may be summarized as: oxygen in. carbon dioxide out; waleI' in, water out. Insects, like all oxygen-utilizing animals. must obtain oxy-gen and eliminate carbon dioxide. This process is called gas exchange (breathing) or external respiration. I nternal respi -ration involves the use of oxygen in the actual chemical processes of aerobic respiration or metabolism (see 12.2.5). In adults, larvae and pupae of insects with complete meta-morphosis (holometabolous), such as beetles and moths, gas exchange occurs by means of tubes (tracheae (pi» branching throughout the insect body that form the tracheal system a (Figure 5.1). Eggs also require oxy~en for development and maintenance and have special shell structures for gaseous exchange (see Chapter 6). Knowledge of the structure and funct ion of the tracheal system is needed to devise logical eradica tion methods that involve gas exchange, including altered atmospheric gases, anoxic environments and some fumigants. Air-carryi ng oxygen enters into the tracheal system through a series of openings located along the sides of the body, called spiracles (Figure 5.1a). There is usually one pair per body segment, though the numbers vary up to 10 pairs. Thespiracles have valves (Figure 5.1c) that are openf"d or closed according to internal and external influences. The tracheal system rami-peritreme Figure 5.1. The tracheal system: a, overall arrangem_enl cif the branches of the tracheal system ill a cockroach; b, details ciflhe relalionship of tracheae and lracheoles; c, detads cf a spiracle with a closing valve adjacent to the trachea (a, bfronl The Hcntokil Library, ivlunroe, 1966 and cfrom Cullell and Cranston, 1994, with permission) . 24 Heritage Eaters fles throughout the body of the insect. It is made up of a network of tubes, tracheae. which branch repeatedly and become smaller and smaller, terminating in tracheoles (Fig-ure 5.1 b). which are the size of individual body cells. T he tracheae are invaginations of the chitinous exoskel-eton and are thus impermeable to oxygen and water. The terminal tracheoles are not lined with wax or chitin and are thus permeable to water; oxygen and carbon dioxide, which diffuse freely, according to the diffusion gradient, in and out of the body cells and body fluid. The tracheae tubes have spiral, ridged thickenings (Figure 5.1 b). called taenidial bars, along their length for strength and flexibility, and to prevent the collapse of the tubes and allow free passage of air. T here are also air sacs. without the taenidial bars, which can increase in size for gas storage. Thisair storage is also a method of reducing water loss. In larval moulting, the old tracheal tubes are pulled out through the new spiracular opening. Xe\\' tracheal structures are formed around the old ones immediately after the latter have separated from the epidermis. Despite the difference in the gross morphology of the holometabolous larvae and ad ul t, the larval tracheal system is preserved in a modified form in the adults . It has been suggested that, in some puparia (hard-ened, protective larval skins), the spiracular structures are larval structures that have been retained in the pupal stage. The tracheal system of the nymphs is the same as in the adults, except for minor size differences. Very little definitive work has been done on the structural changes of the tracheal system from the larva to the pupa. 5.2 Am ~ I OV E~ I ENT T HRO UG H T HE T RAC HEAL SYSTE~ I The movement of air through the trachea is by simple diffu-sion, according to a diffusion gradient, but can be augmented by abdominal contractions which act like a pump, as well as spiracular valve fluttering. Both oxygen and carbon dioxide gases diffuse into the haemolymph (blood) but there are no special cells or chemicals in the blood that are involved in active gas transport. S.3 TH E SP IHACU Ltl H VALV E 5.3.1 Ope ning a nd clos ing of the s p i,'acu la r va lve The closing of the spiracles is essential for terrestrial insects to prevent body water loss. T he opening and closing of the spiracles is caused by muscles which contract or relax to open and close a valve at the opening of the trachea. (A valve is shown in Figure 5.lc). Uthe valve is made of elastic cuticle the muscles have to pull it open, but if not the muscles open the valve and there is an opposable ligament to close it. The spiracles are usually closed to prevent water loss. T he opening of the spiracles for gaseous exchange may be just a flutter ing of the valve. I n some diapausing pupae it has been shown that the carbon dioxide can periodically be mechani -cally blown out of the spiracles. T his cyclic discharge of carbon dioxide is called the Prague cycle (Slama and Coquillaud, 1992). Opening and closing is controlled by an interaction of many endogenous and exogenous factors, i.e. exogenous: tempera-ture, relative humidity, atmospheric pressure, concentration of oxygen, carbon dioxide and nitrogen; and endogenous: insect age, stage, metabolic rate, water reserves and internal oxygen and carbon dioxide concentrations. (For further information see Nikam and Khole, 1989). 5.3.2 T HE IJ'iFL UENC E OF OXYGEN, CA RBON DIOXID E AN D NIT ROGEN ON SPIHACULAH VA LVE OPENING Air contains approximately 21 % oxygen, 78% nitrogen, 1 % argon and 0.03% carbon dioxide, by volume. Both oxygen and carbon dioxide influence spiracular be-haviour. The spiracle opens when the concentration of oxygen is lower or carbon dioxide is higher in the body fluid than in normal atmospheric air. During oxygen depletion and anaerobic respiration in the insect, lactic acid accumulates, which can also stimulate the spiracles to open. An increase in carbon diox ide may cause body flu id acidic conditions, which are suggested to trigger opening of the spiracles. Because carbon dioxide is more soluble in the haemolymph than oxygen, it may be the major in itiator of spiracle response. Pure nitrogen causes the spiracles to open. Carbon diox ide or nitrogen are often combined with fumi-gants to keep the spi racles open and enhance the insecticidal effect. 5.3.3 T HERI\I O REG ULA TION - TE~I PERATURE I'IFLUENC ES SpmACULAR VALVE OP EN ING Insects must maintain a body temperature within an appro-priate range for the performance of normal metabolic activi-ties. They must gain heat but avoid high body temperatures. The environment of the insect may be hot or the in ternal temperature of the insect may increase due to raised metabolic activity. T he insects have little abi lity to compensate fo r environmental temperatures. Insects' behavioural patterns, posture, avoidance of light, etc. usually reflect their thermal sensitivity to their environment. The regulation of internal high body temperature generated by an increase in muscle activity involves haemolymph circulation as well as the spiraculotracheal system. Studies of insect respiration have shown that the tracheal network of insects ventilates excessive air volume at high temperatures and duri ng raised metabol ism (after fl ight). \Vhen exposed to abnormally high temperatures, insects may die because of the temperature effect or dehydration. The effects of temperatures over 40°C can cause death due to denaturation of proteins, enzymes and DKA, all of which are required for life processes. Large insects can sometimes control their body temperature by evaporation of moisture from the body . They do this by opening the spiracles. At reduced temperatures the spiracles respond to oxygen and carbon dioxide down to _5°C but below _5°C the spiracles are frozen shut. At temperatures just above -SoC t he spiracular The tracheal syslem 25 valves should close to conserve body temperature but, ifplaced in 2% carbon dioxide, the spiracles remain open. High temperatures are now being tested as a method of insect pest eradication. The above information suggests that temperature elevated to around 40°C may cause lethal dehy-dration and temperatures about 50°C may cause other lethal cellular temperature effects. Any insect pesteradication treat-ment is as intrusive to the heritage object being treated as to the insect. Research is needed to determine the influence of such a treatment on the materials of the heritage objects. 5.3.4 BODY IV ATER INFLUENCES SP llv \ CULAH VALVE OPEN ING Insects may obtain water in various ways: with ingested food; from oxidation of ingested food; by drinking it; via the tra -cheal system; via the cuticle; and via the anal opening. \Vater loss occurs through the tracheal system and the cuticle. In most insects the exoskeleton or cuticle is water im perme-able because of a surface bpid or wax layer or wax. If this wax layer is destroyed by heat or mechanical abrasion, body water can be easily lost. Only a few insects, i.e. booklice, flrebrats and silverfish, normally adsorb moisture through the cuticle. The cuticle of these insects does not have a surface waterproofing lipid or wax layer. Body water loss occurs mainly through the tracheal system by simple diffusion from the haemolymph into the air in the trachea. The direction of diffusion is dependent on the diffusion gradient between the relative humidity of the air in the trachea and of the external air. There is an interesting conflict between the need to obtain oxygen and at the same time conserve water: opening the spiracular valves brings in oxygen but causes loss of wate r. Fluttering of the spiracular valves may be a method of con-serving water and yet obtaining needed oxygen. The water reserves or state of hydration of the insect influences the spiracular response to oxygen and carbon diox-ide. H ydrated dragonflies in 2% carbon dioxide keep the spiracles open to eliminate the excess carbon dioxide but, if the insect is dehydrated, the spiracles remain closed. This suggests that protection against dehydration has first priority over gases. Insects usually die of dehydration when their body moisture is reduced to about 50% of their total body weight: insects' normal water content is around 80% of total body weight. Spiracular valve closing, a water-impermeable cuticle and excretion of dry faeces are considered the main methods of conserving body water. 5.3.5 SPIRACULAR VALVE ACTIV ITY AND FU,\ II GANTS Even though fumigants have been used for nearly a hundred years, spiracular valve activity under fumigation is still a neglected field. Fumigants may act as an anaesthetic, a nerve or respiratory inhibitor or a metabolic tox in. Thus there will be a different spiracular valve response to each specific fumi-gant. Jt may be that the toxic fumigants themselves do not cause the death of the insect but they are killed by lack of oxygen or by dehydration. The response of the spiracular val ve of the insect pests to eradication treatments using fumigation or altered atmospheric gases is critical to the success of the treatment. For more details on the tracheal system see Bursell, 1974a,b; Gullan and Cranston, 1994; Keister and Buck, 1974; IVliller, 1974; Slama and Cocquillaud. 1992. REFERENCES Bursell , F. t974a. PartA. The insect and external environment. Chapter 2. Environmental aspects~ humidity.]n The Physiologyofinsecla, \ ' 01. II , Ed . .\Iorris Rockstein. Academic Press, New York, pp44-84. Bursell, P. 1974b. Part A. The insect and external environment. Chapter I. Envi.ronmental aspects~tempcrature.In The PhysiologyifInsccta, \ ' 01. n, Ed. :''IIorris Rockstein. Academic Press, New York, pp2--43. Gullan, P.l. and P.S. Cranston. 1994. The Insects: an OUlline ofEnlOmol. ogy. Chapman and H all, London, New York. Keister, ;\1. and J. Buck. 1974. Respiration: some exogenous and endogenous effects on rate of respiration. I n The Physiology of insecla, Vol. VI, Ed . .\Iorris Rockstein. Academic Press, New York, pp47o-509. ;\Iiller, P.L. 1974. Respiration ~ aerial gas transport. I n The Physiology of Insecta, Vol. Vl , Ed. i.\lorris Rockstein. Academic Press, New York, pp346--402. .\lunroe, J .W. 1966. Pests of Stored Grain Products, The Renloki! Library, Hutchinson, London. Xikam, T.B. and V.\·. Kholc. 1989. [nsecl Spiracular Systems. Ellis Horwood , Chichester, p136. Slama, K. and ;\1.5. Coquillaud. 1992. Homeos tatic control of respi -ratory metabolism in beetles. Journal of in secl Physiology, 38( 10),783- 79\. 27 6 The Insect Egg 6.1 EGGS AN D HATC HI l'(G j\losl insects arc oviparolls, that is, the young halch fmm internally fertilized eggs that have been laid externally from the female body. Only in a very few insects do the eggs develop in the body of the female and livillg young are laid. The appearance of the eggs varies with species. They may be oval or elongated and the shells va ry in thickness, sculptur-ing and colour. The design of the sculpturing is species-specific and it assists in species identification. Box 6. 1. shows the sculpturing on some common 1I10th eggs. Certain insects, for example the cockroaches. enclose the eggs in a protective coating or capsule. \ 105t insects lay from a few to hundreds of eggs. The eggs are laid in a specific spot, an oviposition site, where there is some protection, a suitable environment and nutrients for the development of hatched young. The eggs in the oviposition site undergo embryological development and, when this is completed, a young larva or nymph emerges. \Jany of the museum insect pests - clothes moths and beetles - lay their eggs in the materials of heritage objects. The foraging insects, such as cockroaches and book lice, lay their eggs in a different environment from where they feed. T he cockroach is known to look after and feed the newborn nymphs for a day or two. The insect eggs are rich in yolk. :rhere are enough nutr ients and water for embryological development to the nymph or larval stage, but gaseous diffusion must occur. The eggshell is made up of three envelopes: t.he inner serosal cuticle of the em bryo, the vi tell ine mem brane of the egg and the outer hard chorion shell (Fi gure 6.1 ). The eggshell serves to regula te the rates of exchange of gases between the surrounding at.mosphere and the illside of the egg and to conserve water. The oxygen molecule is larger than the water molecul e so there must be,some system to allow free movement of the larger oxygen and at the same time to restrict the loss of water. 6.2 EGGS HELL STilL CT LJ IlE The serosal cuticle of the embryo acts as a livillg membralle with its permeability controlled by osmosis. 1t separates the amniotic nuid of the developing larva from the vitellin mem-brane. Sonobe and Kakamura (1991) suggest.ed that the sero-sal cuticle formed after 24-:)6 hours of incubation may be involved in the control of oxygen absorpt.ion. The vitell ine membrane and chorion are non-living and act as permeable membranes involved in passive diffusion. The wax layer covering the vitellin membrane functions to pre-vent water loss. In dennestids' eggs without a chorion there are a large number of slightly raised regions (O.511m in diameter) on the exposed vitelline membrane. These regions have a multitude of wax canals, which replenish wax lost by abrasion or preda tors (Furneaux and :\ l ackay, 1976) . T he chorion is made up of a structural protein called chorionin. I t derives its strength and insolubilit.y rrom disul-phide-cross lin ked or quinone- tanned proteins. T he majority of terrestrial eggs have a meshwork ill the chorion, which holds a layer of air (Figure 6.1). T he meshwork is made up or aeropyles or holes that extend throughout the shell to give a continuity of atmospheric and chorion gas. Aeropyles. tubes of very small diameter, connect the meshwork or the inner chorion with the outside atmosphere. It is the aeropyle open-ings on the surrace of t.he cho rion that give the chorioll the sculptured surface (see Box 6.1) . The innermost layer is a thin, solid sheetof cllorion. T he chor ion with its aeropyles functions as a plastron, all ai r bubble gill. like the air bubble the diving beetles carry with them when they di\'e in water. Some insects VCR-leAL COI1JMN Figure 6.1. Seclion cfthe rhorion sheIL ofaf! l:nsect egg showing the pla.slron nelff"ork alld m:rji.lLed ol.llerlaxer underlying ii, the meshwork cf vertical columns if the inner la)'er and the aeropxles belween (after }-fin Ion. 1970). 28 Herilage Eaters have the plastron restricted to a respiratory horn or localized regions on the chorion. The plastron also prevents a n oxygen deficiency when the egg becomes wet. The chorion addition-ally acts to protf'ct the intact ness of the wax laye r of the "itelliTle membrane. At the anterior end of the egg, the micropylar area, there are a number of openings for the f'ntrancc of spe rm. Their ornate shapes, showlI in Box 6.1 , assist in species ide ntification. Lepidoptera eggs may have meshworks so finC' (Furneaux and \l ackay, [976) that they cannot be seen with a light micro-scope, whereas in other insect eggs the aeropyles are easily \"isible. l n Dermestes, the chorion is \'ery thin or absent. For further information on eggshell structure, see ~\rbogast el al. ( 1980), Arbogast el ai. ( 1983), Arbogast e/ al. ( 1984), Arbogastand Brower ( 1 989), I linton ( 1969, 1970) and Furneaux and \ lacka)" ( 1976). 6." 1'l"'\CTIO.' OF T il E EGGS II ELL 6.5.1 Intl'oduc ti on The following reviewed studies, on the function of the egg-shell regarding oxygen and water permeability and temperature tolerances, arc on specific insect species. Thcy describe activitics that must be common to other insects. There is species variability but the underlying phenomena must be uni\"ersal. The purpose or this review is to provide a background for understanding th(' actions of eradication methods using al tered atmospheres, reduced oxygen and temperature extremes. Cnfortunately, there is a great lack of inrormation directly applicable to the heritage eater insect species, but this re\"iew will act as a knowl('dge base on which to add. 6.5.2 Ox~'gen pe rlll ca bilit~ Oxygen requirements vary with the size of embryo and stage of development. Daniel and Smith ( 1994) stud ied the oxygen requirements of developing eggs alld compared the results with adults. Callosobruchus mandalus, Yemen strain, eggs 1-2 days old had an oxygen requirf'ment of 8.S9!J.l per day and those 6- 7 days old required 23.52!J.l / day. They attributed the increase in oxygen to the change in metabolites used, rrom carbohydrates to fats. Fats require up to three times the amount of oxygen when Llsed in anaerobic respiration. This type of increase was also shown in the oxygen needs or the pupae during diapause (see chapter 8). Xon-feeding adults Llsed 7S-82!J.l per hour. at a constant rate. The weight dirfer-ences were 25.5~ for eggs and 5.3mg for adults. The eggs during development required one third more oxygen per unit of body weight than adults. The respiratory quotient (H.Q) has been observed during t1w de\"elopment of the egg and the general picture is that, at initiation, the H.Q is close to I, with a rapid drop. This has been attributed to the utilization or dirferent ellergy sources, i.e. first carbohydrates then fats cOl1\"ert.cd Lo carbohydrates. 6.5.3 Oxygen I'eq u il'cm e nls (!LII' ing dia pa ll s(' Insect eggs usually go through an obligatory stage of develop-mentdelay called diapause.lt isa stage of low nwt.abolism and low oxygen consumption. I fthe egg in early embryonic devel -opment goes into diapause, the assumption has been that the permeability of the chorion would decrease just before d iapause. Hccent work (Sonobe and ~akamura , (991) on the silkworm egg shows. however, that the permeability of the chorion to oxygen does not change appreciably wi th the onselof diapause, eycn though oxygen consumption decreases. These research-ers also demonstrated that it is not caused by the lack of acceptance of oxygen in the electron transfer system in oxidati\"e respiration (see chapter -5). They suggested that the serosal membranes playa role in oxygen absorpti on control. 6.3.4 Pl'evenl ion 0 1" wa tc r loss Even though the water molecule is smaller than the oxygen molecule and the pore size of the chorion has to enable the larger of the t.wo molecules to move th rough the shell, water loss is minimal. The most important aspect of egg survival is pre\"ention of water loss. In some dry terrestrial insect eggs only sma ll specialized areas of the shell may be permeable to gas and the majority oft.he shell is hard, smooth and imperme-able. This is the case in the bean weevil, Callosobrochus ma.cula/us (Daniel and Smith, 1994). These investigators showed that a single opening in the chorion, the egg pore, was solely responsible for gas diffusion by plugging it with oil; the egg suffocated and died. T he gas permeability of the insect eggs makes them vuln('l"able to altered atmospheric gases used as a method of eradication. 6.'f Il ES ISTAS CE OF EGGS TO LO\\' T E\IP EIl ITLIl E Low-temperature insect pesteradicat.ion methods are covered in 12.!. \Yith silkworm eggs, Yamashita and Yaginuma (1991) showed that the number of days of incubat ion influences resistance to low temperatures. Eggs were initially incubated at. 25°C for various lengths of time prior to 2'~ hours' treatment at _20oe, then returned to 25°e to continue incubation. For eggs with an initial incubation of one day 78% hatched after cold treatment, with 2 days' initial incubation 15% hatched, and with nine days incubation 0% hatched. Earlie r stages were more resistant to low temperatures than later stages. Yamashita and Yaginuma (1991) also showed that the diapause egg was 1I10re resistant to low temperatures than the non -diapause egg because of their lower super cooling point (the temperature at which their body fluids freeze). On the other hand, Gray el al. (199S) rcported no difference in resist -ance to low temperature of the diapause and non-diapause eggs of the gypsy moth. "fhis limited information demon-strates the variability of responses to low temperature due to egg physiological state and species. 6.5 1.\IPLIC ITI O"\ S FO il Ell 10ICAT IO.'i .\IETII OOS The literature on eradication methods by temperature ex-tremes and anoxic ell\"ironments (s('e chapter 12) contains many reports on the success of the treatments. Such success is detennined by the death of the insect tested. Unfortunately, in 'I 'he lIlsect e~{! 29 . ~ JO Heritage Eaters ~ ~ "-"J '"' ,... 0 :;s > 0 :;s ~ 2 '" ;s: 0 "J '" 0 "J (.) (.) ~ ~ <; "'-'" '" 0 '" ~ The Ul\e([ e{!{{ J I '" ~ ~ '" '" :--:--0 "'" '" >0 ;;. ~ 2 ~ 0 '" "-0 '" v v ~ ~ g '<5 '-< 0 '" " 32 [-ferilage Eaters nearly all cases the cause of death is not known. It is possible that low and high temperatures, as well as anoxic conditions, could result in death due to dehydration. It is also reported that large amounts of the anaerobic carbohydrate metabolism products polyols, alanine and lactate, accumulate prior to diapause. T hese are substrates that can be used without oxy-gen, by anaerobic respiration, to produce adenosine triphos-phate (ATP) needed for cellular maintenance. I t is important to note that these same chemicals are produced w hen insect larvae are subjected to stress from low or high tem peratures and from dehydration. T his further supports a common re-sponse to stress from differen t origins. 6.6 BI OLOGY O F EGGS OF COM~ION I-1 ERITAGE-EATING INSECTS Thesize of the eggs, length of incubation and number laid will vary greatly with t he nutritiona l state of the adult and the envi ronmental parameters, so these data are no t used as a means of identification. H owever, the following information from the li terature may help to identify the origin of the eggs or aid in the process of removing eggs. Tineola bisselliella, webbing clothes moth. T he eggs are about lmm long, oval, ivory white, w ith narrow ridges . T he eggs are attached to threads by a gelatinous material and are not easily shaken off. The time of hatch ing varies with environmental parameters: 4 days-3 weeks. • Dennesles maculalus, hide beetle. The eggs are 2mm long, creamy in colour. • Auagenus megalOma (:::: piceus), black carpet beetle. T he eggs are ve ry fragile: a vigorous brushing or shaking will remove and kill most of them, whereas moth eggs are more sturdy and withstand more abuse. • A nlhrenus verbasci, varied carpet beetle. T he eggs are 0.27mm wide by 0.55mm long; the egg surface is rough wit h a short spine-like projection at one end . Eggs are white when first laid but become cream-coloured during development. Trogoderma inciusum, large cabinet beetle. The eggs are 0.5mm long, with a hair-like projection at one end, wh ich adheres to any surface it contacts. • Anobium punclalum, common furn iture beetle. T he eggs are whitish, ellipsoid, 0.35mm wide and 0.55 long. They resemble an acorn, with the cup being an alveolate area with small pits, aeropyles. • P linus leclus, spider beetle. The eggs are sticky when fi rst laid and become covered with particles of food and debris . T hey are O.47-o.55mm in length and O.29-0.40mm in width, and are opalescent. Tenebrio molitor, yellow mealworm. The eggs are bean-shaped and sticky but become covered with meal and debris. Blalla orientalis, oriental cockroach. An ootheca, an egg case in which fertilized eggs develop, is carried by the female until the young are ready to hatch. The m other tends the young nymphs for several days in their nursery. REFERENCES Arbogast, R.T., G.L. Lecato and R.V. Byrd. 1980. External morphology of some eggs of stored-product moths (Lepidoptera: Pyralidae, Gclechiidae, T ineidae). [nt. J. Insect i\1orplwL Embryol., 15: \65-169. 1996. Arbogast, R.T., G. Chauvin, H. .G. Strong and H..V. Byrd. 1983. The egg of Elldrosissarcitrella (Lepidoptera: Oecophoridae): Fine structure of the chorion. 1. Stored Prod. Res., 19: 63-68. Arbogast, H.T. , R.V. Byrd, G . Chauvin and R.G. Strong. 1984. The egg of Hofmannophila pseudospretella (Oecophor idae): Fine structure of the chorion. J Lepid Soc., 38: 202-208. Arbogast, R.T. and J. I-I . Brower. 1989. External morphology of the eggs of Tinea paliescentelia Stainton, Tinea occidentelia Chambers and NiditineaJuscella (L.) (Lepidoptera: Tineidae). lnt.. 1. Insect NlorphoL Embry-oL, 18 (5/ 6): 321-328. Arbogast, R.T. 1996. Personal communication. Research Entomologist, Center for Medical Agricultural and Vetcrinary Entomology, U.S. Dept of Agriculture, Gainesville, Florida . Daniel, S.I-I. and R.H . Smith. 1994. Functional anatomy of the egg pore in Callosobruclllls maculatus: a trade-off between gas-exchange and protective functions. Physiological ElIlomology, 19: 3D-38. Furncaux, P.J.S. and A.L. 1 lackay. 1976. T he composition, structure and formation of the chorion and vitelline membrane of the insect eggshell. In The Insect I nlegumelll, Ed. J-l.R . Hepburn. Elscvier Scientific, Amsterdam, Oxford, New York, ppI57-176. Gray, D.H., r.W. Ravlin, J. Regniere and J. A. Logan. Further advances towards a model of gypsy moth (Lymantria dispar (L.» egg phenology: respiration rates and thermal responsivcncss during diapause, and age-dependent developmental rates in postd iapause. Joumal if insecl Physiology, 41(3):247-256 lI inton, H.E. 1969. Respiratory systems of insect eggshells. Anf/ual Review of Entomology, 14:543-568. I-l inton, L.I .E. 1970. I nsect eggshells. Scientific American, August, pp84-91. Sonobe, I-\, and ;\ 1. Nakamura. 1991. A re -visitation of the oxygen permeability of the chorion in relation to the onset of embryonic diapause in the silkworm, Bombyx mori. Journal ciflnsecl Physiol-ogy,37( 10P27-731. Yamashita, O. and T. Yaginuma. 199\. Silkworm eggs at low tempera-tures: implications for sericulture. I n Illseclsal Low Temperatures, lids. H.E. Lee and D.L. Denlinger. Chapman and Hall, New York, London. }} 7 The Larva: the Eating Machine 7.1 INTRODUCTION An insect egg hatches into either a ian'a or a nymph. The larva is the feeding stage of insects that have complete metamor-phosis (holometabolous), such as beetles and moths. The larvae are caterpillar, wire worm or grub-like in appearance. .'\yrnphs are sexually immature juveniles of insects with incomplete metamorphosis (hemimetabolous), such as cock-roaches, silverfish and booklice. Both larvae and J1)'l11phs undergo a series of moults as they grow. The young insect that hatches froln the egg is called the first instar. This stage ends with the shedding of the old cuticle and from it emerges the second instar. Thus an instar is the growth phase between two successi\"c moults. The different larval instars , of one species, are similar in appearance but yary in size. They never resemble the adult form, whereas the nymph instars always do. and, after each successiye moult, there is a stronger resemblance to the mature adult. The larvae have a different diet and lifestyle from their adults, whereas nymphs usually compete with their adults for the same food and habitat. It is mainly the lan"ae of the holometabolous insects and the nym phs and adults of the hemimetabolous insects that are the heritage eaters. Details of the biology of nymphs are discussed under their adult forms (see chapter 9). 7.2 THE LARVA Even though larvae cause nearly all the damage in holometabolous insect infestations, rarely are they studied or identified. \\'e have a mind -set directed towards the 'adult' insect, which rarely causes direct damage to heritage objects. Their role in life is distribution and reproduction, which is of course a concern in control of insect pests at all levels: build -ings, storage areas and drawNs. Our fixation on the adult insect must be because they fly - we see them, we can catch them. In contrast, we rarely see larvac, catch them, or e\'en look for them. I n most books or articles on museum and household insect pests (Freeman , 1980; Hickin, 1972; H inton, 1945; H inton and Corbet, 1972; Pinnige r , 1994) there are e legant illus-trations, biology and identification keys for the adult.s. with often only a little information on the identification and biology of the larvae. Jf present. th is information is often from a few sources such as II inton (19·~5, 1956) and Rees (1 H5, 1947). 1n entomological taxonomic literature, Peterson's (1967) and Stehr's (1987) works discuss the taxonomic features of larvae in all insect families and ha\'e excellent photographs and illustrations, but there is very lillie information on the biology and identification of the lan'ae of museum or house hold insect pests. I n treatises on specific groups or families of insects, such as Robinson 's (19 79) work on Tinea peltionella complex, and Scobie's (1992) The Lepidoptera, there is some information, but again it is buried in thc taxonomic literat.ure along wit.h t.he larvae of a multitude of other species. Peacock (1995) has presented excellent illustrations of the hide, carpet and larder beetle larvae and has made points on identification, but again there is lit.tle on t.he biology of the lalTae. Even in this entomological literature t.he authors often refer to Hinton (1945) and Hees (1947). There is, however, a large group of papers on the digestion of keratin by t.he larvae of clothes moths and dermest.id beetles. triggered by the economics of the wool industry. There is also an extensiye body of literature on cold-hardiness and anoxic tolerances of larvae, triggered by the need for non -chemical erarlication methods in the stored food industry, as well as basic biology. The following is a compilation of rele\'ant information from all of this literature and general entomology t.ext books (Gulla n and Cranston, 1995; \ \'iggleswort.h, 1984) it. is sparse but. significant. 7.2.1 General morphology of larvae There are three common functional forms of lalyae, polypod (many legs), oligo pod (few legs) and apod (without. legs). • Po(ypod lar\"ae ha\'e cylindrical bodies with t.hree pairs of short thoracic legs and abdominal pro legs. The most com -1I10n examples are Lepidopt.era: but.terfly caterpillars and moth lalTae. • Oligopod lan'ae lack abdominal prolegs and have func-tional t.horacic legs. The most common examples are in Coleoptera: larvae of dermestid beetles, carpet beet les and stored food beetles. I Jeritagc Eaters 2bdominal legs presenl MOTH LARVAE Ihor<ICic legs present 2bdomin21 legs 2bsen! ~ BEETLE. BORER & ~_I_EA __ L_\I7_0 _ R_M __ L_A_R __ V_A_E __________________________ ~1 . wilh fl esh y lobes 2t ends of body without fleshy lobes 2t ends of body FLEA LARVAE head opsule present ~ t~WEEVIL LARVAE MUSCOlD FLY LARVAE FIj!:lIre 7.1. fJtuonaL kC.l to ('0111111011 p:mups (y/tc)/Jle/to/d alld \/orl'dji)()r/ IN\IS: /arra/ \fa!!c\ (SU)fI. /959, I .S U I IH II . Ipod lan,w lack tnH' Ipg!>. and ar(' lI!>.udlh worlll ,llIag-gol or grub Ilkt'. Ttl(> IIIO!>.t ('OlIlIIIOII P,\ilillplp!>, an' wood b('('l l p dlld \\t'('\ il Ian ,-H', 1)('(' and \\<1';P grubs <-I1lc! fl, I l laggob. I n Figllre i.1 a pictorial k('\ to COll11110n gr()UP~ ()f h()I I ~('llold ,II HI <'IOf('d food IW"" li1nal"'li:lg('~ illu"tr,1tl''>t!Jl''>t' thfe(' I'I)('!>. of Ian iH'. i.2.2 Biology of larvae T he blOlog\ of I ht'lIlIlIIat lIr(' ,>lage.., of 1I1';('C\ .., I'; ('oH' fed III f u ll III gC·l1pr.l1 PIllOIIIO\Og\' t(''\ 1 hook" and iourn,ll.., (e.g. ( ;1l 11a1i <Ind tfanqOll, 1<)<);: \ \ Iggl(''>worlh, Il)H"i; \\ Ipkltlg cl a/., I C)<)"i). Onh rl'i('\illit a';j)('('I<;tilat aid undefstand ingoft he' pr(,\(,llt io li aJl(i ('radKill l oli of 111~('('\ IH'ntagp ('at(,f~ af(, pn'<'(' lI ted h(,fe. The lan'a: the eating machine J5 7.2.2,1 Ff~f.DI\G.FOOD 1\/)F17 a Feeding ,\ list of the types of heritage objects and materials that have been infested by insects would be too lengthy to be practicable and would tell us little more than that nearly all organic materials and soiled synthetics, as well as metals, can be attacked. Some of the material damaged has been eaten by larvae and adults for food, some by larvae digging out pupa-tion sites and some by larvae tunnelling through it. The insect heritage eaters can be grouped according to where they live and the type of food they appear to eat ~ but remember, there is an exception to every rule. The environmental indicators: those that live and breed in one place in the building and visit foodstuffs and materials elsewhere. Both nymphs and adults feed and their pres-ence tells us there is something wrong, somewhere, in the building's environment. Xymphs and adults of cockroaches. ants, crickets, booklice, silverfish. termites, Food: starch, sugars, oils, protein gelatin, fungi, wood, etc. 2 Those that live and breed ill the foodstuffs and in sornc cases move away from the food to pupate, Adults and lan'ae feed. For example: Dermesles lardarius, larder beetle; P linus leclus, Australian spider beetle; Tenebrio species (spp), meal worm; Trogoderrna (spp), hide beetle; 5legobium paniceum, drugstore beetle; La.sioderm.a serricorne, Ciga-rette beetle, Food: stored dry food products (spices, dried plant and animal material, cereals, nuts, dried fruit), Occasionally these insects damage wood for pupation. Those that feed and breed in natural organic materials of which heritage objects are composed or synthetics soiled with natural organic materials. Adults may fly and feed on pollen or nectar but not on the food of the larvae; some larvae may move away from food to pupate. For example: clothes moth and house moth: Tineola bisseLlieLla, Tinea peLlioneLla, Ilofmallllophila pseudospreleLla and the carpet and fur beetles: Alllhrenus L'erbasci, A llagenus pellio. Food: keratin in fur, feathers, wool, etc.; skin. dried animal tissue and blood: soiled natural and syntIH>tic fabrics; some plant materials. 4 Those with larvae that bore into wood and are able to subsist on wood kept in buildings, Only larvae feed, For cxam pie: woodworm,A nobium pUllctatum; powderpost bectle l~yclUs brwmeus, Pood: cellulose, starch and protein in wood, fungi in wood. Lost sou ls: fortuitous wanciercrs from the garden or else-where outdoors. For example: house fly, lIusca domeslica, ladybird beetle, fungus gnat, etc. Food and food supplements .\·early every type of organic material is eaten by some insect larvae, but it is not always clear if they digest what they eat. For example, some larvae eat large quantities of wood but digest only the fungi present, whil e others may utilize only the associated starches and proteins in the wood. :\13ny insect larvae may attack keratin materials (wool, horn, tortoiseshell, feathers) but cannot digest this protein. These larvae and adults, i.e. termites, silverfish, larder beetles. khapra beetles and white-shouldered moths, are eating through the materials to get to the other side Of are eating the associated materials or soil spots on the materials. The larvae that attack insect collections do not have the ability to digest the chitinous exoskeletons. but feed on the fatty materials normally present in the adult insectspecimens. The only animals that can digest keratin are insects and, in the insect world, only a few can do this. The protein keratin of wool, hair. horn, etc. is resistant to normal digestive proteolytic enzymes, and is insoluble in most solvents. Tineola bisselliella, the common or webbing clothes moth, has been shown to digest keratin ( \\'aterhouse, 1958). It has digesti\"e juices that are alkaline (pIJ 10) and a reducing em'ironment in the midgut that causes the initial breakdown of the keratin pro-tein, The strongdisulphide bonds in the keratin are reduced to more soluble sulphydryl bonds, which are then acted upon by the proteolytic enzymes that digest the protein. The midgut does not have any trachea and has a thickened wall that is basically impermeable to oxygen, so it is able to maintain anoxic conditions for a reducing environment. Some carpet beetle larvae (Anthrenusverbasci, the varied carpet beetle, and Allagenlls picells. the black carpel beetle) have also been shown to digest keratin. Keratin is not a very nutritious food and the larvae that eat it also eat other materials such as dried fish or meat, ground grains,caseill, protein in bones, dead rodents, etc, T hesaltsand vitamins in urine and sweat stains on wool are also very attractive to the keratin eaters. Synthetic fabrics are often thought to be insect-proof but it has been demonstrated that both clean and soiled synthetic fabrics can be destroyed by clothes moths and carpet beetles. Bry ( 1991 ) showed that larvae of the furniture carpet beetle (Allthrenus flavipes), the black carpet beetle (Allagenus ullicolo,) and the webbing clothes moth (Tineola bisselliella) grazed lightly on synthetic fibres of dacron, nylon. viccara, dynel and rayon but as a comparison they fed extensively on mixtures of wool/nylon, wool/orlon and wool/viscose rayon, These same insect species we re given a group of synthetic textiles (100°'0 acetate, 100°'0 polyester, 100°0 nylon. 100°0 acetate tricot. 50% polyester/ 50% acrylic, 50°0 polyester/ 50% rayon, 80% triacetate/ 20% nylon and 60% rayon/ 300 o polyester/ l00:o linen bonded to acetate tricot), which had spots of acidic perspiration , artificial alkaline perspiration, ketchup, chicken bouillon. mustard, and 5°'0 sugar. The lan'ae of the three species damaged the synthetic textiles and the black carpet beetle and webbing clothes moth did most dam -age when the textiles were spotted with ketchup. The most feeding occurred on 100% acetate contaminated with ketchup J6 lIeritage Eaters and the least on clean or soiled polyester fabric. The moral of the story is that their favourite food was ketchup. These six contaminants are only a Loken sample of the possiblespols tllal occur on textiles, but the results show that these insect species can damage soiled synthetic textiles, supporting the necessity to clean textiles before storage. Another feature of the digesli\'c system of the clothes moth larva is that it is able to ingest large amounts of metals and then detoxify itself. This is of importance regarding the resistance of the clothes moth to metal-based mothproofing chemicals. \Yhich nutrient supplements insect larvae can synthesize is still not well documented. \Yhat the larvae cannot synthesize, e .g. sterols and fat soluble vitamins. they need in the food they eat. Sterols are required for structure, moulting and develop-ment and vitamins have a variety of activities. Perspiration and urine are common sources or these supplements. Symbiotes living in the larva's gut, for exam ple yeasts and bacteria, may supply vitamins (the vitamin B group) and some amino acids that they cannot synthesize. It has been shown that bacteria digest cellulose for utilization by the termite and the Lasioderma serricorne (c igarette beetle) larva hassymbiotes that produce the vitamins it requires. c F al - lhe fal body The instar larvae are the active, growing, food-consuming stages of the insect's lire. The purpose of the larva is to eat and to store enough food energy ror pupation and the emergence and maintenance of the reproductive adults. :\ot all larvae reach this goal because of insufficient food, bad genes or adverse environmental conditions. I nside the larva, the most conspicuous structure is a large fat body made up of loose sheets or ribbons or fat cel ls. The fat body in the larva is like the liver in mammals, a group of specialized cells in which rat, glycogen and proteins are stored, and the site or intermediary metabolism. The tissue is sturfed with mitochondria, suggesting its metabolic role. The fat body reaches its full development in the late stages of the last instar of the larva: the stored chemicals are used for pupation and adult emergence. Some adult insects that do not feed, e.g. carpet beetles and clothes moths, have remnants or the rat body, which supplies the energy for flight and reproductive activities. Theadult house fly, even though it feeds, has a large fat body (carpet beetle larvae are commonly found inside the abdomens or dead house flies, which obviously take advantage of this free energy source). The fat body is an organ with a multitude or functions: metabolism of carbohydrates, lipids and nitrogenous com-pounds; storage or glycogen, rat and protein; synthesis orblood sugar, egg yolk, and blood and storage proteins. The amounts of the chemicals in the fat body change during larval develop-ment. Glycogen accumulates towards the end or larval life, reaching up to 33% or dry weight. Fat or lipid levels fluctuate: they are high in the early stages, drop and rise again at maturity. Protein levels drop if the larva builds a cocoon. Uric acid, the waste productorprotein metabolism, is usually stored as crystals in t.he fat body. The crystals accumulate in the lar\'al instars and are passed on to the pupa or adult ror final el imination. Trehalose is thesugarcommonly stored in the rat body and its level fluctuates with metabolic activity. Tn the last instar the rat body cells become dissociated , but sometimes reassociate during the formation of the pupa, to form a rat body for the new adult. d Ol.ygen requirements Larvae have shown unusual resistance to low levels or oxygen as an adaptive response to environments of low oxygen, such as rolling logs (0.5°"0 oxygen), stored grain (1.8% oxygen) and in animal stomachs. The larvae or the horse bot fly can tolerate levels of 0.1 0"0 oxygen in the horse stomach (\ 'Yigglesworth, 1984). By comparison there is 21% oxygen In air. During diapause and exposure to low temperatures the larval oxygen requirement is reduced, reflecting a reduced metabolic rate (see Figure 8.4 in chapter 8). Iligh temperature and muscular activity cause an increase in oxygen demand. The rate or lan'al development may be influenced by reduced amounts of oxygen. Tests with the larvae or the grain beetle (Tenebrio mohlor) showed that, when exposed to levels of 10.5% oxygen, the rate or larval growth was slower and they underwent more moults but reached the same size as larvae in 21 % oxygen (Loudon , 1988). Altered atmospheric gases, including low oxygen or anoxic conditions, are suggested as methods orinsect pest eradication ror museum and household insect pests. Details or these methods are given in 12.2. For rurther inrormation on larval oxygen rquirements, see \Yigglesworth ( 1984). c IVater - nor any drop to drink Larvae do not drink water. so they obtain water rrom their rood (dietary water), from water vapour through external respira-tion or surrace absorption or rrom water bound in chemicals (metabolic water). They muslconsen'e water in their body by reabsorpt ion of the water in their gut and by prevention of loss through derecation, respiration and transpiration. Some organic materials are more vulnerable to insect at-tack not only because or their odour but also their moisture content. Certain adults and nymphs (booklice, silverfish) ha\'c sel'lsory organs that detect moisture. but most larvae appear to have only odour-detecting olractory sensilla on mouthparts, which hel p them with rood selection. The energy expendi ture orlarvae depends on the amount or dietary water ( \Tan't I lof and :\ lartin, 1989). Low water con-tent in food causes reduction ill growth rates, and increases in respiration rates and oxygen assimilation. Iligher metabolic activity is required ror reabsorption of water rrom the gut and an increase in the time required ror feeding to obtain surricient water. This illustrates the importance or moisture content (:\ lC) in the food of larvae. T here are many reports on water content (:\ IC) tolerances in the rood or some insect heritage eaters, but the parameters are so \'ariable that the information is not very useful. Environmental fluctuations in temperature and relative humidity ( RI L) that alter the:\ IC of materials can cause de\-elopmental changes in larvae, such as periods of quiescence, moulting and pupation. The bottom line is: the drier the material, the less vulnerable to insect attack. The interaction between the H 1-1 or ambient air and the structure or the organic materials or heritage objects with rererence to :\ IC is discussed in chapter 2. The lan'a: the eating machine J7 " Tater vapour absorption does occur in the soft-bodied booklice and silverfish. and the larva of Tinea pellionella is able to adsorb water vapour through the cuticle from unsatu-rated air at 93% HII (Chauvin and \ Ta nnier, 1980). l~ nder water stress some insects can extract water from chemicals, e .g. the last instar larvae of the wax moth (J indra and Sehnal, 1990) was shown to extract metabolic water from the food it was eating. :\letabolic water is a byproduct of oxidative catabolism of carbohydrates and fats. Larvae under stress from cold temperatures or anoxia pro-duce polyols (glycerol or sorbitol) in their body fluids, which help to conserve water. T he polyols bind water, which lowers the vapour pressure, pre\'enting normal di ff usion and consen'-ing the water (see 12.1.1 ). For further information on larvae feeding, see H ouse (1974) and \Yigglesworth (1984). 7.2.2.2 !!.;\ IIRO\ HE\ 1:' TUIPt.:R..·I/"l Rt.: 1\/JRI I The fact that we find insects in objects in heritage collections of all types tells us that microenvironments support their development. There may not be optimum conditions but the heritage eaters survived. \Ye can try to determine why the insects were able to lin" in this specific microenvironment and, if it was because of an environmental (temperature and RI I) prob lem, we can solve it. Booklice and silverfish are excellent indicators of problems in building environments. As mentioned above, the most critical aspect of the environ-ment for the insect is the moisture content of the material, which depends not only on the environment but on the material itself. In most cases the elwironment docs not determine the location of the insect acti\'it)': it is probably by chance that infested materials were placed in that spot and the insects SUT\"i\"ed. The environment we supply in our museums and homes doubtlessly provides optimum conditions for most insects: we cannot change this. but we can stop the insects from entering. The integrated insect pest programme discussed in chapter 13 is a preventive approach wh ich does just that. 7.2.2.) SIGHT I\/J 1.1&'111" Larvae do not ha\"e the ocelli or compound eyes found in adults, but they may ha\"e one or several pairs of stemm at a on each side of the head (Figure 10.3). Stemmata are different from the simple eyes, the ocelli, of the adult. A typical stem rna is composed of a single light-refracting unit (cuticular lens), a few light -isolating structures (crystalline body or three rhabdoms) and the light-sensing components (ocular nerve) (Scobie, 1992). T he stemmata produce a well -focused image w ith poor resolution because of the few cells involved. lepidop-tera larvae usually ha\"e six stelTUl1ata on each side of the head. \\-hen they turn their head back and forth the), obtain a mosaic of the visu¥al fie ld. Larvae usually move away from light. 7.2.2. '~ f)OR\lI\O, /)f II' 1/.,1-;, Ql 1/';8("/:.\U; 'rhe development from an egg to an adult insect is often interrupted by a period of dormancy. If brought about by the ('nvironment, this is called quiescence. but if it is caused by an Internal physiological state, it is called diapause. Quiescence is a slowing down or halting of deve lopment as a response to all adverse environment, e.g. low moisture, and is broken as soon as the external environment is suitable for continued develop-ment. Diapause is the halting of development by some inter-nal physiological state. Anyone of the stages (egg, nymph , la rvae or pupa) can pass into a more or less prolonged state of arrested development or di apause: this can last a few days or months. It is most common in overwintering insects where a photoperiod response is somet im es needed to increase a hor-mone level to break the diapause. 1n developing pre pupal larvae there is a juven ile hormone present wh ich in hibits mou lting, thus maintaining diapause (see 8.3). Once t he juve-nile hormone is metabolically broken down, the m ou lting hormone, ecdysone, is produced, the di apause is broken and moulting and then pupation occur. T he use of the juvenile hormone has been researched as a method ofi nsect population control by preventing pupation . T he cause of dormancy may not be obviolls: it is di fficult to determine if a dormant period is a period of quiescence or d iapause. T he larvae of different instars and developmental stages suggest a potential for a large variat ion in metabolic states, but there is a clear difference between diapause and non-diapause lan'ae. \\' ipking el al. (1995) com pared the physiological states of diapause, in itiated by short daylengths of LD 8: 16 (8 hours light: 16 hours darkness), and non -diapause moth larvae (LD 16:8). At 20°C, in the diapause, compared with the non-diapause larvae, the respiration rate was red uced by about 77°"0. the levels of lipids, g lycogen and water by 50% and the oxygen consumption by 70-80% (varying with weigh t). Even though this work was carried out on a specific moth , these results suggest a clear characterization for dia pause. T hey are similar to those presented for the pupa in diapause (see 8.4 and Figure 8.2). It is suggested that d iapause occurs in insect popu lations in museums and hOlnes. The cause may be an adverse environ-ment, most probably related to low moisture in the materials of the objects- tl1(' insects' food -or it is genetically controlled . An increase in the numbersof adult insects occurred about two weeks after an accidental increase in hum idity in a museum (see 2.3.2), suggesting that the increase in moisture broke the diapause of the last instar or pupa and adult emergence was triggered (see 2.3.2.3 for more details). Diapause has a popu-lation survival benefit if pupae are synchron ized so tha t adults emerge at the same time to ensure partners for mating. 7., ~I O R P IIOLOG ' O F LAIl YAE OF SO~I E II EIlITAGE EAT EIlS T he larvae of the Lepidoptera and Coleoptera are the main heri tage ea ters. Details of morphology are summarized here; for further information, see Peacock ( 1993), Pe terson (196 7), Scobie ( 1992) and Stehr (1987). 7.3.1 Lepidopte ra Ia n ae Illo l'pho logy: Ge nera l c ha r'acte r' istics • polypod form • distinct head sclerotized • chewing mouthparts, mandibles opposable, toothed and visible JS [jerilage Eaters • one pair of short antennae • typically six slemmata protruding labial spinneret • three pairs of rive-jointed thoracic legs 10 abdom inal segments • pairs of prolegs with crochet on segments 3, 4 , 5, 6 and 10 • spiracles on prothorax and abdominal segments 1-8 CL ISS I FlCAT IOS OF CO l LI lOS CST LCP I DOPTEIIA HEIl IT.IGE E.ITEIlS Tincoidea Tineoidea Tineidae 'l'/:neola bisselliella, Tinea pel/ionella, 7i"ichophaga lllpet::ella Gelechiodea Oecophoridae 11c!inannophila pseudosprellella, Endrosis sarcilrella There may be many other species lhalarcof particular concern to YOLl. By using the references cited it is possible to research these species and add a personal appendix to this book. TL\E ID I I:: (CLOT II ES .11 0'1'11 , CI::IlE I L 11 0'1' 11 , II'OOL 110'1' 11) LAIlI'A - .11 0IlP Ii OLOGI C.IL FE.lT UHES Figure 7.2 shows the overall structure of '!'iIJeapellionella, the casemaking clothes moth and Tineola bisse/liella, the web-bing clothes moth. :\lature larvae range from 6-50mm long. Tile body is cylindrical , moderately slender and naked except for primary setae (hairs) . The cuticle appears smooth but. with minute spinules. The body is usually whitish cxcept for an Figure 7.2. The overall slruclUre oflhe lar7'ae ofT illca pellionella, the case-making clothes moth (A - E) and Tineola bisselliella, the u'ebbing clothes moth (F-J). A alld F, dorsal/'iell ' of head and prothorax; Band C, lateral vieli' of head; C and II, middle l,ieu' ofn:ght mandl:ble: D alld 1; crochets of sixth abdominal. right proleg; E and J, crochets ofri{dtt al1al pro/ego (Lanxle, f{o"yal British Columbia .1-luseum, by Anti Iloll"att -Krahll: A - J. Peterson, 1967, lrilh permission.) Figure 7.3. The head pOsl:lion of larvae and adult insects (after Ste/,,; 1987). almost black head and thoracic plates. Hound spiracles are located along the abdomen. The head capsule, shown in Figure 7.2, is heavily sclerotized. It has setae and sensilla (sensory hairs) in specific arrange-ments which assist in identification of the species. The head is hypognathous (pointed downwards; Figure 7.3) in position: that is. the head is directed vertically, with mouthparts di -rected ventrally. The larvae have chewing mouthparts, even though their adu lt form has sucking or vestigial mouthparts. In Figure 7.4, scanning electron micrographs show the awesome complexity of a moth larva's mouthparts (Tinea translucens). ~o wonder they are called heritage eaters. The mandibles are well devel -oped, heavily sclerotized and bear molar and incisor areas. They are opposable and, when brought together, they inter-lock. The labrum (lip) , which overlays the mandibles, and the jointed maxillae located below the mandibles, both push the food into the grinding mandibles. Sensilla, olfaClory hairs, are located by the mandibles so they brush up against the food to assess its mechanical and chemical qualities. Silk is exuded from large silk glands in the thorax and head, into the tube-likespinneret (Figure 7.4) situated on the under-side of the head between the maxillae. Awr-:Y, B ,, ' C<\·I '. I C tA ~("''''KI~~ C. /'I fi'fM0·, I· ~, " " . :: .. )1")1((<" :.~ J 11'" , I ::,.llIlf'~ ~ ,,~ The lan'a: the ealm/{ lilac/line J9 Figure 7.-+. Sranning eleclron micrographs oj the mouthparts larrG o/Tinea translucens \/efrick. ·\ shoU"s the/ron tal ",iell' Icith the mouth cavity surroun!led by the bottom spillnerel and the ma.xil/ae at its sides, and the top labrum") beloll' lFhich are the paired mandibles. Small antennae are at each side oJthe mandible. 13 ShOlFS details oJthe spinneret and paired maxillae (from Davis, /987. (Filh permission). Some larvae live for all or part of their liw''> in silk cases, which offer some means of protection. l ..arvae usually build a silk cocoon for the developing pupa . .\ web of silk threads is often associated with cereal moths and webbing clothes moths. There are one to six stemmata (the number depending on the species), which give a mosaic impression of the field of \·ision. The antennae are short. at segments 3-4. Sensory openings are usually located on the second segment. There are three segrnents to the thorax.,.c\ thoracic spiracle is located in the first segment. Each segment has a pairof \\'ell~ developed, five~joillted legs, which terminate in a cla\\". These legs are similar to the adults'. The abdomen usually has \ 0 segments. Five of the abdomi-nal segments, 3, ,~ , 5. 6 and 10, have a pair of soft prolegs, fleshy outgrowths of the body wall (Figure 7.5) . Each proleg has a base and terminal planta (so le). The planta bears a circle of small retractable hooks called crochets, structures by which the larva hold on to the material on which it is feeding. T he crochets allow the larva to walk finnly o\'er a surface, and they can even walk on \'ertical. smooth surfaces by secreting a silk pad which sticks to the surface and gi\'es a firm grip. The arrangement of the crochets is related to the lan'a's mode of life and in the 'Tineidae they are in a uniserial ellipse or circular arrangement (Figure 7.5). The crochets and silk pads make the larvae tenacious wall clim bers. BIOLOGY I:\D I LLL STRHI O.\S OF Sml E LEPIDOPTEIlA Uill I E HEIlITI GE EATEIlS The Lepidoptera family is large and information on the larvae sparse. The most useful reference is I-l inton ( \956). T r·ic hoph aga tapctzc ll a, lapes tl'Y 01' , \ hit e -tip clothes moth The larvae usually infest coarse rnalf'riais such as horsehair upholstery stuffing and skins. They construct rough silken Figure 7.5. ProLegs oJTineidae lan·a. AbOl;e. diagram oJthe lchole proleg (after Scobie. 1992). Beloll". seal/fling electron micrograph sholl'ing the uniserial, ulIiordinal arrangement 0/ the crochets (from Dat'is, 1987, U'ilh permission). 40 Herilage Eaters tWlneis in the infested material that are smooth inside but outside appear rough because of the camouflaging pieces of fibre or hair and faecal pellets. The larvae spin a tough cocoon for pupation. T illeoLa bisselliella, " ebbing clothes moth (Fig u,'c 7.2) The larvae are caterpillar-like, creamy white with a golden brown head. They are extremely small, 0.1 mm when hatched, and can crawl into crevices equally as small. Larvae spin a loose webbing, by which they are recognized, and may make feeding tunnels. The iarvae are active and may be found on the floor below an infestation, hunting for a pupation site. The larvae drop and move away quickly when alarmed. They crawl away from light. T i fl ell. p ellionella, case-making clothes moth (Figu l'c 7.2) The larva is easily recognized by the case it spins, which is open at each end, and the larva drags it wherever it goes. The larvae die, probably from dehydration, if they are removed from their cocoons. They may move to a protected area, such as ceiling or floor crevices, to pupate; they pupate in the case after sealing it at both ends. The larval cocoon is made of silk to which the larva attaches chewed pieces of the material it is eating, so the cocoon mimics the colour of the material. Other species: Tinea pallescellle//a, large pale clothes moth. J !o!ma1lllopIJila p seudosprelella, hl'own hOllse moth General body colour is white and uniformly glossy, with head and first dorsal plate sclerotized and chestnut brown. The larvae are seldom less than 16mm. Before pupation, the larvae go into diapause. which can last 71- 145 days. The life span of larvae is 192- 140 days in cultures, 12 months in nature. The larvae remain naked until they enter diapause or pupation , when they spin a cocoon (that tears like paper) and remain in the tube while feeding. The last larval instal' is a wandering stage, which leaves its food to hunt for a hiding place (e .g. corrugated cardboard) for pupation. The larvae have been reared on a wide variety of both animal protein and plant carbohydrate. Th e best development occurred on dead adults. Endrosis sarcilrella, "hite-shou lde l'ed house moth The larva is dull white, with rows of shiny spots representing the dorsal plates; it rarely exceeds 14mm in length. The larva eats carbohydrates, proteins and dead insects. There is no diapause: the larva wanders for a short period of time and then spins a cocoon and forms a pupa. Corrugated cardboard has been used for larvae to spin their cocoons on; the cocoon tears like cotton-wool. 7.3.2 CO LEO PTEIl I L I llI .I E .110 IlPIi OLOGY, GE;\EIU L CII III ICTE Il ISTI CS • oligopod form • head capsule well developed and sclerotizcd terglle _____ --' median longitudinal line retrorse tubercle acrotergite ____ --,,~:;;g;;;; anterior transverse ridge urogomphus(i) ~ 9'" ." 10 , ~. , ~'I spinulate setae 1 posterior head thoracic segments (thorax) abdominal segments (abdomen) Figure 7.6. Oermestes maculatus, hide beetle, larva, to show morphology (from P eacock, 1993, with permission). • antennae almost always wilh four segments or fewer • number of slemmata on each side six or fewer • mouthparts chewing with opposable mand ibles moving in a transverse plane • labial silk g land and spinneret always absent • thoracic legs usually five -segmented • abdomen usually 10 segments • prolegs absen t • spiracles with accessory openings The larva body form varies from elongated and slightly c-shaped to fat, grub- like and strongly c-shaped. Figure 7.6 shows the larva of the hide beetle, Derrnesles maculatus, to demonstrate Coleoptera morphology. CLASS IFICAT IO'l OF CO~1 1I I ONEST COLEOPTEIlA II EIl ITAG E EAT EIlS (Slehr, 1991) Bostrichoidea Denneslidae Dennestes, 7'rogoderma, A nlhrenus,A llagenus, Plinus, Thylodrias, l\Jegatoma Bostrich idae LyclUs Anobiidae Anobium, Xeslobium, Stegobium, Lasiod.erma Ptinidae Plinus, \IIen=.iwn, Gibbiurn, Nipusi The larva: the eating machine 41 Tenebrionoidea Tenebrionidae Tenebrio MORPHOLOGY, BIOLOGY AND ILLUSTRATIONS O F SOME COLEOPTERA LAR VAE HER ITAGE EAT ERS De rmestidae, d e rmestid beet les (h ide, la rde r and ca l'pe t beetles) The most valuable sources on dermestid morphology are Hinton (1945), Rees (1943) and Peacock (1993) , who provides an excellent illustration and discussion of the anatomy and characteristics used for identification, as well as keys for identification and the biology of the adult Dermestidae bee-tles and larvae. The majority can be recognized by their hairy appearance and brown dorsal plates. The larvae are oligopod larvae (they lack abdominal prolegs) and have functional thoracic legs. The general morphology of the dermestid beetle larvae is shown in Figures 7.6 and 7.7. The body is elongated and subcylindrical not curved when viewed from the side. It is densely covered with long or short spiny setae (hairs) and sometimes with hastisetae (see Figure 7.1O) (hastisetae are spear-shaped segmented setae unique to Dermestidae). Three pairs of thoracic legs are five-jointed , with tarsus and claw fused into a single claw-shaped terminal segment. The abdomen is 8- to I O-segmented without prolegs. Figure 7.7. Dermestes larvae. Above lift, D. lardarius, larder beetle; above right and below, D. maculatus, hide beetle. (From Peacock, 199J, wilhpermission.) Some species have caudal brushes of hastisetae or long straigh t spicisetae (barbed setae) at the tip of the abdomen. The head is visible from above, free and hypognathous (pointed forwards: see Figure 7.3), that is, directed vertically with mouthparts directed ventrally. It has a pair of opposable, brown, sclerotized mandibles which are more brown on top than on the bottom, and are distally rounded with 2-3 apical teeth. There are no silk glands or spinnerets. The thorax is short, one-quarter-two- fifths of the length of the abdomen, and has three pairs of five-segmented thoracic legs, with the claw fused with the terminal segment. The abdomen has nine or ten segments and no prolegs, and there are conspicuous tufts of setae on the posterior tergites (seg-ments). The larvae eat mainly dried animal matter, e.g. woollens, feathers, hides, dried meat, dead insects and exuviae (cast skins) of insects. These pests are cosmopolitan and have spread through commerce. '\lost adults eat only pollen and nectar but some species (e.g. Dermestes and Thylodrias contractus) are found feeding in the same habitat as the larvae. The following are the most common Dermestidae larvae reported to be heritage eaters. Theirdietismainly proteinaceous material of all kinds. Only salient features are mentioned. T hy lodrias contraclus, odd beetle This larva (Figure 7.8) feeds on feather, fur, carrion, dead insects, zoological collections of insects, birds and dried ani-mals.1t is oval-shaped and light golden brown, with a row of hairs on each body segment that are club-shaped, clavate spiciseta. The female adult may be m istaken for a larval form because of its soft, larviform structure. The larvae curl up when disturbed. Figure 7.8. Larva ofThylodrias contractus, odd beetle (from Peacock, 199J, with permission). 42 Heritage Eaters Dermes tes Im'da rius, lal'd e r 01' bacon beetlc; Dermesl.es macula tus, hide bee tl e Larvae (Figures 7.6 and 7.7), when hatched , are white but soon become dark. They are very active in the dark but feign death in the light. The last instal' larva moves away from the feeding site and bores into surfaces to make pupal chambers. Both adults and larvae feed together. Before it lays eggs the adult female eats the same food as the larvae. \Yhen there is adequate food , faecal pellets are excreted in bead-like chains. The larva (Figure 7.7) has dark, strong, bristle- like tufts of hair along its body , which is lO-15mm in length and has dorsal extensions. urogomphi , on the ninth ab-dominal segment. The last abdominal segment is encircled by a sclerotized ring. A Uagellus 1I11icolor, black c a"l>e t bee tl e The larvae are hairy and characterized by posterior tufts of long hairs. caudal setae. T hey avoid light and feign death if disturbed (curl up and play possum). They have a banded appearance and their exuviae show this feature. Other species: Altagenus pellio, fur beetle, two-spotted carpet beetle (Figure 7.9). Figure 7.9. Larva cifAttagenus pellio, two-spotted carpel beede. Lejt, dorsal view; centre, scale-like setae,. right, dorsal lateral viell' (from Peacock. 199J, {I'ilh permission). variabile tefglte~ _ __ ~= !/~ / l\\~: \ I ~ ~ b~ c~ inclusum g/abrum Figure 7.10. Larvae ofTrogoderma spp., cabinet beelles, Centre, 7: glabrum, dorsal view: middle right, side view of apical abdomial segments. Enlargements cif hastisela from T rogoderma spp., as marked· b, setafrom abdorninal sergile 1; c, setafrom caudaltufi ofabdomillallergile 6 (front P eacock, 199J, wilh permissl:on). Trogodermll. inclusum, lal'ge cab ine t bee tle, mottle d de l'm estid fhgJp'A' ) W,r t. ., 't ~ /'i.4-"1< This light Ir'own larva (Figure 7.10) ~s spear-headed, with setae and_~~~isetae present on the back and a long brush of hairs , spicisetae, extending from the posterior of the abdomen. It has dorsal extensions, urogomphi, on the ninth abdom inal segment. T he last abdominal segment is encircled by a sclerotized ring. Adults and larvae appear to feed together. Larvae wander to a pupation site. Other species: Trogoderma granarium , khapra beetle. Heei;'a vespulae, museum nuisan ce, cal'l>et beetl e This larva is light brown , a similar colour to Trogoderma , and found on all types of museum collection: botanical , entomological , skin , fungi , seeds, as well as in paper and textiles. The larva: the eating machine ~J antecostal suture Figure 7.11. Larvae ofAnthrenus spp., carpet beetles. Above left, A. verbasci, dorsal vielD: above right, A. verbasci, side view; below, A. Oavipes, dorsal vielD (from Peacock, 199J, lL-'illz permission). AlIl.hrenus verbasci, ,'a l·je d ca l'pe l beetle The larvae (Figure 7.11) are 4-5mm in length, much fatter than Allagenus larvae and are often called woolly bears. They are often found in cracks in wOQden floors and under base boards in dust. They are brown and hairy, with a bunch of special golden hairs, a caudal brush, on each side of the rear abdominal segment on the supra-anal organ. The larva is able to raise and vibrate this fan -s haped mass of hastisetae as a defence mechanism. The hairs are shaped like arrows and their details assist in identification of different species. The spiny setae deter predators and the hastisetae may become attached to the attacker and, while it is cleaning them off, the larva can escape. If the larva is disturbed, it rolls up and fans out the posterior hairs. The larvae avoid the light and pupate in their food, commonly when this food is a dead insect. The larvae are very active and move around quickly and widely. Other species: /1 nthrenusjlavipes, f urni ture carpet beetle (Fig-ure 7.11 ); Anthrenusfuscus, furniture carpet beetle;Allthrenus scropulariae, common carpet beetle, buffalo moth . .. Viegatoma undala, carpet beetle, I / Figure 7.12. Larva ofLyctus brunneus, brown powde'post beetle (Royal British Columbl:a 'lduseum, by Ann Hou'alt-Krahn). BOSTIlI C HIDAE (BOSTltJ C HOID EA). WOOD BEETLES, PO II'D EIlPOST BEETL ES, TWIG A.'1D II'OOD BOil ERS The larva (Figure 7.12 shows an example) can be 3-60mm in length, but is usually less than 20mm. The body is elongated. subcylindrical or slightly flattened, moderately or strongly cu rved ventrally (c-shaped) , lightly sclerotized except for a dark mouth with a whitish to yellow cuticle and a few scattered dorsal simple setae. The head is retracted and prog-nathous, elongate and somewhat flattened , with three-seg-mented antennae. Lye/liS brunnclls, powde rpost beetle The larva (Figure 7.12) lives its life in wood. \Vhen it is first hatched in a crevice or pore of the wood, it is creamy white and less than a cpntimetre in length . .I t has dark brown, sclerotized mandibles and a strongly arched body . The thoracic legs have three segments, the last of which is paddle-shaped. A pair of breathing spiracles on the last, eigth abdominal segment are large and easily seen. The larva usually eats along the grain but does cut ac ross other tunnels. It cannot digest cellulose and hem icellulose: it lives on cell contents, starch, sugars and some proteins and thus is restricted to sap wood (hardwoods). The larva attacks parquet floors and oak panelling. It is frequently imported in hardwoods from the tropics. The moisture contentof wood is 8-50v,u; the optimum for this larva is 16~'o. Kiln -dried wood is protected from LyclUs bruflneus attack. The frass consists of fine particles with a silky feel. 44 Heritage Eaters Figure 7.13. Larva ofL yctus planicollis, southern lyclus beetle. sp=spiracle. md=mandible (from PetersolL 1967, with permission). LyClus planicollis, soulhe ,'n lyc tus beetle, true powde rposl hectle This larva (Figure 7.13) infests many kinds of dry, seasoned hardwood, especially ash, hickory and oak. ANOll li DAE (BOSTR IC HO ID EA), FURN ITURE, DEATHWATC H, DR UGSTOH E AND CIGAR ETTE BEETLES Powderpost beetles, spider beetles and anobiids have the following in common: strongly c-shaped, well -developed legs, lightly sclerotized body and a pair of longitudinal, oval anal pads or cushions just below the anal opening, which prevent the abdomen from touching defecated faeces. Anobiids differ from lyctids by having protracted and hypognathous heads and very short antennae. The anobiid larvae can be from 2-12mm in length, having a c-shaped body that is lightly sclerotized with a nearly black, heavily sclerotized mouth, and, usually, fine hairs. The thorax has three pairs of well -developed, five-segmented legs. The head is globular to flattened; the mandibles are symmetrical, robust and un identate to tridentate. IVOOD BEETLES Anobium puncllll.um, commo n furn itur"c bectle, fa lse po wde r'pos t beetle, furnitlll"e w oodwor'rn The larva (Figure 7.14) lives its whole life in wood. It can only be observed by breaking open the wood in which it is living. It is arch-shaped and has three pairs of we ll -developed tho-racic legs, each with five segments. The larva usually tunnels upand down the grain of tile wood. The tunnels are filled with rejected wood fibres and barrel -shaped faecal pellets, which give the frass a grainy feel. Figure 7.14. Larva 0/ Anobium puncta tum, commonfornilure beetle, woodworm (Royal British Columbia Museum, by Ann f-lowatt-Krahn). Xes lobium rufoviUosum , d eath watc h beetle This larva is similar in appearance to AnobiumpunClalUnl, the common furniture beetle, It has two black spots on each side of its head, while A. punctalUm has just one. The larva is creamy white and strongly hook-shaped, is covered with erect golden hairs and grows to about a centimetre in length. The newly hatched larvae move over the surface of the wood to find a crevice or trough to enter the wood. Frass is in the form of bun-shaped pellets. CEREAL- AND PROTEi N- EATING BEETLES Slegobium p a fliceum, drugs to re beetle, bread beetl c, biscuit beet le This larva (Figure 7.15) has a head that is protracted and hypognathous. It is nearly white, except for short, light-coloured setae (hairs) all over the body. Larvae and adults move around freely in stored food, spices, dried soup mixes, flour , etc. The larvae mature in 4- 5 months and grow to 5mm. Figure 715. Larva ofStegobi UJll paniceum, drugstore beetle (from Peterson, 1967, with permission). The larva: the ealing machine -15 Figure 7.16. Lwva of Lasioderma serricorne, cigareue beetle (from Peterson, 1967, with permission). Lasiode r'm a serricol'll c, c iga r'cUe bcet le The larva (Figure 7.16) is nearly while, except for many long setae on the body. They shun light. Larvae and adults appear to feed together. They are commonly found in tobacco, where the larvae make long cylindrical galleries in the compacted leaves, but they also feed on other plant material and spices. PTI i'i IDA E (BOSTRI CHOIDEA) SPIDER BEE1LES The spider beetle adults and larvae feed on the same food. They are scavengers of a wide variety of animal and plant material: faeces, hair, feathers, textiles, exuviae, dead in-sects, etc. The larva can be 2-6mm long (see Figure 7,17 for exam-ple). I ts body is elongated, moderately curved ventrally (c-Figure 7.17. Larva ofPtinus brunneus, spider beetle (front Peterson, 1967, wilh permission). shaped) and lightly sci erotized with fine hairs. The head is protracted and hypognathous, and it is heavily sclerotized. Stemmata are absent, antennae are very short and mandibles are symmetrical. robust and wedge-shaped, with a simple unidentate apex. The abdomen has anal pads. Okumura (1982) discussed the biology of adult spider beetles. There is very little reference to the larva. Ptinus tcetus, Austr'ali a n spide l' beetle The larva is a whitish, fleshy grub that is strongly curved. It rolls up into a tight ball when disturbed. The body is covered with hairs and the thoracic legs have claws. " Then mature. the larva wanders away from food to fi!1a a suitable pupation site. It may eat its way through tough hlaterials such as sacking, cellophane and cardboard for pupation, at which time it builds a spherical, thin-walled, tough cocoon. Other species: Gibbium psylloides, hum p spider beetle ]\]e=ium americanum, American spider beetle (Figure 7.18) ~VilpUS hololeucus, golden spider beetle Plinus bfunneus, spider beetle Ptinusfur, white-marked spider beetle Ptinus hirlellus, brown spider beetle Plinus villiger, hairy spider beetle Figure 7.18. Larva of;\Jezium americanum, Arnerican spider beetle (from Peterson, 1967, wilh permission). REF EHE.\'CES Bry, R.E. 1991. Synthetic fabrics and fibre pests. JoumalofEtUomologi-cal Science, 26( I ):51-58. Chauvin, G. and G. \ '-annier, 1980. Absorption of water \'apour by the larvae of Tinea pel/jor/eILa (L.) (LepidopteraTi neidae). Experienlia, 36,87-88. 46 J-i erilage Ealers Box 7.1 KEYS FOR IDKVTIFICATION OF LARVAE OF COMMO,V CLOTHES MOT/-! AND BEETLE HE1UTAGE EATERS C lothes m ot hs (Tineidae) Abbreviated key for identification of the commonest clothes moths, according to silk structures: a Larvae live in elliptical, flattened cases covered or spun with infested material, open at both ends: Tinea pellionella, case-making clothes moth Larvae live in silken fibres and rough tunnels in the infested material: Triclzophaga tapet::ella, tapestry moth naked larvae not hairy may form a silken tube or burrow through material c Larvae associated only with webbing: TineoLa bisselliella, webbing clothes moth naked larvae not hairy associated with webbing and faecal pellets head yellow to light brown without ocelli HofmannophiLa pseudospretelLa (brown house moth) and Endrosis sarcitreLla (wh ite-shouldered house moth) are in the family Oecophoridae, which differs from the family Tineidae by arrangemen t of setae on the thorax and of crochet hooks. Tineidae have an elliptical or circular Wliserial crochet arrangement and Oecophoridae an ellip-tical or circular biordinal arrangement. Beetles (Coleoptera) Abbreviated key for identification of the commonest Coleoptera larvae (collated from Stehr, 1987): A Larvae are not fuzzy, the head is protracted and prognathous (pointed forwards), they have two pygopods present on the 10th abdomen segment and are without sci erotized ring, and they are associated with stored products: a exoskeleton stiff, wire worm-like dark brown Tenebn:o obscurus, dark mealworm i i yellow, golden brown Tenebrio molitor, yellow meal worm, grain beetle b exoskeleton soft yellowish white Trilobium caslaneum, rust-red flour beetle, grain beetle Trilobium. corifusum, confused flour beetle B Larvae are fuzzy, not grub-like, the head is free and hypognathous (head pointed downwards): a larvae is spear-headed with setae (hastisetae) on back long brush of hairs extending backwards from posterior of abdomen; spear-headed setae arise from abdomen segments Trogoderma T granarium, khapra beetle T inclusum, large cabinet beetle T ornalUm, cabinet beetle ii three pairs of caudal tufts or brushes at posterior region ofabdomen;spear-headed setae arise from between abdomen segments Ant/zrenus (larvae indistinguishable) A.jlaVl:pes, furniture carpet beetle A. scroplzulariae, common carpet beetle A. verbasci, varied carpet beetle Larvae without spear-headed setae on back long brush of hairs (spicisetae) extending back-wards from posterior, head free and hypognathous Aaagelllls A. megaloma, black carpet beetle A. pellio, fur beetle A . piceus, black carpet beetle Megaloma vespula, carpet beetle ii larvae are fuzzy, have long spicisetae, with pair of processes at the tip of the abdomen, urogomphi on the ninth segment, sci erotized ringencircling the last abdominal section, reassociated with protein material Derm.estes lardarius, larder or bacon beetle Dermestes maculatus, hide beetle c larvae with short, thick hairs (lanceolate spicisetae) across rear edge of each body segment, head free and hypognathous hairs are club-shaped on rear edge of the prothorax, rolls up like a pill-bug Thylodrias contractus, odd beetle C Larvae are not fuzzy, lightly haired, grub-like, they have three pairs of well -developed thoracic legs, no pro legs, head is protracted and hypognathous, stemmata are absent: a Thoracic spiracles located near front of prothorax larvae with light-coloured or colourless setae all over the head, peanut-shaped spiracles Stegobiumpaniceum,drugstore beetle, bread bee-tle, biscuit beetle. No distinct colour markings, mouthparts and underside of are head brown ii larvae have yellowish brown setae in a face-like pattern on head, spiracles annuliform to oval Lasioderma sern:conze, cigarette beetle. Long, light-coloured, more fuzzy than above, setae located on all parts of the body Thoracic spiracles located near posterior of pro thorax Spider beetles P tinus fur, whi temarked spider beetle Ptinus lectus, Australian spider beetle The wood beetles are not included here because larvae are rarely found; also, the bore holes on infested wood are commonly used for wood beetle identification. The larva: lhe ealing machine Da\-is, H.D. 1987. Tineidae.ln lmmalure lnsects, \'01. I, E.d. F.\\' . Stehr, F.W. Kendall / llunt Publishing Company, Iowa , C5A, pp362- 365. Freeman , P. 1980. Common II/ sect Pests of Stored Food Products. A Guide to their [denlUtealioll , 6th E.d. British \Iuseum (.\"awral Ilistory) Economic Series, London , .\"0. 15 Gullan , P.J. and P.S. Cranston. 1995. The Insects: An Outline of Entomology, Chapman and Iiall, London, .\"ew York. llickin, '\".E. 1972. The lI 'oodworm Problem. The Bentokil Library, I-I utchinson, London. I linton , II.E. 1943. The lan'ae of the Lepidoptera associated with stored products. Bulletin of Entomological Research , 34: 163-212. Hinton, II.E. 1945. Ll/oflograph of the BeetiesAssociated {L'Llh Stored Products, \'01. 1. British \Iuseum (.\"atural I l istory), London. I-linton , I I.E. 1956. The lan'ae of the Tineidae of economic impor-tance. Bulletin of Entomological Research, 47:251-346. Hinton , H.£. and A.S. Corbet. 1972. Common insect pests of Stored Food Products. British \Iuseum (i\atural il istory ) Economic Series i\o. 15. London. Iiouse 1l. L. 1974. 1"\utrition. In The physiology ofLnsecta, \ ' 01. 5, 2nd Ed. , Ed. \Iorris Bockstein . . \ cademic Press, .\"ew York , ppl-62. Jindra, \1. and F. 5ehnal. 1990. I.inkage between diet humidity , metabolic water production and heat dissipation in the larvae of Galleria mellOflella. insect Biochemistry, 20(4):389- 395. Loudon , C. 1988. Development of Tenebrio molitor in low oxygen le\'els. Journal of Physiology, 34(2):87- 103. Okumura, G. 1982. Stored product pests. In Handbook of Pest Control, 6th Ed. , Ed. A. \Iallis. Franzak and Foster Publishing Comp., Cle\'eland , Ohio. Peacock, E..H. 1993. Adults and Larvae of I-Iide, Larder and Cafpet Beetles and Their Relatil'es (Coleoplera.Dermestidae) and of Derodontid Beetles (Coleoptera: Derodontidaej. I land books for the l dentification of British lnsects, \ ' 01. 5, Part 3. Hoyal E.nto-mological Society of London , London. Peterson , A. 1967. Lan:aeojlnsects, Parts 1 and 2. 6th E.d .. Edward Bros, Ann Arbor. \lichigan. Pinniger, D. 1994. Iin sect Pests in Huseums. Archetype Publica -tions, London. Bees, H.E. 1943. Classification of the Dermestidae based on larvalcharacteristics , with a key to the :'\orth American gen -era. C.S. Department of Agriculture. \liscellaneous Publica-lion 511: 1- 8. Bees, B.E. 1947. Taxonomy of the lan'ae of some :'\orth American species of the genus Dermestes (Coleoptera: Derrnestidae) . Proceedings of the Entomological Society of IVa shington. 49( 1 ) ,'~'4. Bobinson , G.5. 1979. Clothes moths of the Tinea pel/ionel/a complex: a revision of the world's species (Lepidoptera:Tineidae). Bul-letin of the British \Iuseum (A"atnral Il istory), Entomo!' Series, 38(3) :57- 128. ScobIe, \1. 1992. The Lepidoptera FOri/I, Function and Diversity. Oxford Cniversity Press, :'\cw York. Scott, lLG. 1959. Household and Stored-Food ["sects of Public liealth importance and Their Control. C.S. Department of Public Health , Educat.ion and Welfare. Atlanta, Georgia. Stehr, F. W. 1987 1991. Immature Insects , \ 'ols I and II. Kendall / Il unt Publishing Company, l owa, USA. \ 'an't Ilof, 11.\1. and ~ I .\I. ~ I artin. The effect of diet water content on energy expenditure by third -instar ,Handuca sexta lan'ae (Lepidoptera:Sphingidae) . Joumal of inseCl Physiology, 33(3),433-436. Waterhouse, D.F. 1958. \"Yool digestion and moth proofing. Ad~ vances in Pest Control /{esearch, 2:207- 262. Wipking, \\T., \1. \' iebahn and D. :'\eumann. 1995. Oxygen con -sumption, water, lipid and glycogen content in carly and late diapause and non-d iapause larvae of the Burnet \ loth Zygaello trifolii. Journaloflmert Physiology, 41 ( I ):47- 56. Wigglesworth, \' .8. 1984. insect PhXsiology, 8th Ed. Chapman and lI all, London and ~ew York , ppl91. 47 49 8 The Pupa 8.1 P UPATIOi'( SITE " Then a mature larva is committed to metamorphosis it continues to feed to reach its critical size. It then ceases to feed and leaves the food in search of a pupation site. This is called the wandering stage and is triggered by hormones (see Figure 8.1). The wandering larva decides on the pupation site, possi~ bly the feeding site on the heritage object or it may seek out a suitable protected pupation site away from the feeding site. Often the pupae are not seen because they are in chambers or cocoons made by the larva, or away from the larval feeding site. Pupation sites can be tunnels or pupation chambers made by the larva beneath the surface of compact materials, such as wood, or in cracks and crevices in the walls, ceiling or floor close to the larval feed ing site. The fact that the pupation site may not be on the infested heritage object means th at, in the event of an infestation, one must inspect the insect remains to be sure that all stages of the life cycle, including the pupae, have been found and removed . T here have been frequent instances where the pupae have not been located and, after a clean-up, there was a reoccurrence of the infestation from these hidden pupae. T his has often been blamed on unsuccessful eradication methods. 8.2 PUPATION In the group of insects that have complete metamorphosis (holometabolous), the final instar or mature larva that has completed feeding, called the prepupa, goes through struc-tural and morphological changes in preparation for metamor-phosis. This period is called pupariation and is still a larval stage. I t is during the larval-pupal moult that metamorphosis occurs and the pupa is formed; this process is called pupation. The pupa is an intermediate, non-feeding stage that moults to produce an adult insect. Commonly during pupation, the larval structures are dis-solved and new adult structures dpvelop from a group of undifferentiated embryonic cells caii ... d imaginal discs. These cells divide, differentiate and form the pupa, which is e ncased in a new, heavily' sclerotized cuticle (see 4.3.2). It may be further protected by a larval cocoon ora puparium. The cocoon is spun silk and the puparium the sclerotized moult of the prepupa larva. The pupa can be an immature or fully formed adult. If fully formed, it usually remains dormant in the pupal case for a period of time. T he dormant period, called the diapause, allows the pupa to survive adverse environmental conditions, e.g. overwintering. \Vhen environmental conditions are con-ducive, the adult emerges. T h is is a way to synchronize the emergence of many adults at one time to ensure mating and survival. In museums or homes the occurrence of a la rge number of adult insect pests of one species, atone time, suggests that there has been an environmental change, usually an increase in relative humidity, which has broken t.he diapause of pupae and tr iggered emergence of the adults. For further information on pupation, see Denlinger and Zdarek (1994) and Gullan and Cranston (1995). 8.3 PUPATION UNDER HOR~IONAL CONTHOL P upation is controlled by the relative amounts of the juvenile and ecdysteroid hormones (Figure 8.1). T hese two hormones are secreted internally from the endocrine gland, the corpus alia tum, located behind the brain. The juvenile hormone (JH ) is required to ensure that, when a larva moults, it remains as o 2345678 ------4t~h~I.-N-.~,-~-.9-.-----+' 1 +-------~5~,h~I.-N-.7,~SI~.9~.--------+ prepupal stage t_pharate pupal Figure 8.1. Fluctuations in the relative amounts a/the juvenile hormone (JI'I) and ecdysteroid (ES) during the last two larvaL stages and the prepupal stage. The diagram shou:s the presence a/high JH and low amounts 0/ ES coinciding with ecdysis (moulling) a/the Larval stage. The reverse, low JH afld high ES, triggers the deveLopment o/the larva to the prepupal stage (afier GuLLan and Cranston .. 1995). 50 Heritage Ealers 2.0 r--------, ~ 5~I\V\ U ::;- I 0 a. :::l a. . ";: 0 5 ," o i 0 1\../\ ~~g .6 o 50 100 PUPAL AG E % O2 CALCULATED O2 DIRECTLY O2 FROM FAT O2 FROM CARBOHYDRATE RO DIRECTLY RO CALCULATED Figure 8.2. The o.rygen cOl/sumption alld respiratory quotient during metamorphosis ofthejZy Calliphora crythr.ocephala, directLy measured 01/ Living pupae and calculated from estimations if the gradual disappearance iffat and carbohydrate (from AgreLl and Lundquist, 19iJ). a larva in the next stage. JH is no longer produced in the flllal insta r larva but there isan increase in theecdysteroid hormone (ES). The reduced amount of JI-I and the presence of ES activate the imaginal discs and direct the larva to proceed to the prepupal stage and undergo pupation . The production of these hormones is triggered internally in the endocrine gland, probably by the nutritional status of the larva and environ-mental conditions (Gilbert and King. 1973). J 1-1 is used in agriculture and forestry to contro l insect pest populations by preventing pupation. L l owever. this extends the life of larva, the reverse of what is required for the control of heritage eaters. 8.4 ~IETABOLlS.\1 OF P UPA The pupae of the common insect pests of heritage objects are inactive; their body movement is restricted to the abdominal segments, probably related to external respiration or breathing. The pupa is a non-feeding stage. The food needed for emergence comes rrom the fat body, proteins and glycogen of the mature larva . The goal of the larva was to accumulate these nutrients for the development and reproduction of the adult. Hesearch has shown (Agrell and Lundquist, 1973) that during pupal l ife the main food utilized is fats. T his is meas-ured by the amount of oxygen required and the amount of carbon dioxide produced to convert this nutrient into heat energy. The ratio of these two gases is called the respiratory quotient (RQ), the ratio of CO , evo lved to 0 , consumed . The RQ is dependent on the sourc~ of energy b~ing utilized, e.g dextrose 1.00, protein 0.8, fats 0 .7. In Figure 8.2 the ratio is around 0.7, suggest ing utilization of fat for energy. During pupal life , oxygen is required for respiration to produce the chemical energy ror metabolic processes. Figure 8.2 shows that oxygen consumption is high at the initiation of pupation, then drops to a low level and remains there until just prior to emergence, at which time it rapidly becomes high again. The period of low oxygen consumption is the diapause. The length of time of diapause varies with insect species and environmental conditions. Figure 8.2 illustrates the adsorp~ lion curve of oxygen for pupae of one insect species, but this u-shaped curve is common to many species. The relevance of this information to heritage eaters is in relation to anoxic insect pest eradication treatments. The low oxygen consumption ofthc diapause pupa suggests that it may require a longer treatment time than active stages. It is possi ble that. in the future, pretreatment to induce breaking of d iapause would make the anoxic treatment more rapid. Details of the effects of anoxic conditions are reviewed in chapter 12. 8.5 PI\ EVENTION OF IVAT EI\ LOSS The pupa has no way of obtaining water, so it must conserve as much internal water as possible. T he sclerot ized cuticle, puparium or cocoon of the pupa must prevent body water loss. Body metabolic wastes are not eliminated during pupal life, also conserving water. There is, however, water loss when tracheal spiracles open to acquire essential oxygen. Beetle pupae have spiracle valves to control the opening. Some diapause pupae store carbon dioxide and eliminate it in one dai ly burst, which shortens the time needed for spiracles to be open, thus reducing water loss. The low consumption of oxygen during diapause also limits water loss. T ests have demonstrated that an increase in carbon dioxide in the ambient a ir causes beetle pupae spiracles to open . Jt is the open spi racles that cause body water loss and even tually lethal dehydration, not the gas cond itions. T his in for mation assists in understanding the vulner-ability of the pupal stage to eradicatio n methods using altered atmospheric gas concentrat ions. In tests with modi -fied atmospheric gas concentrations th e cause of death is often not determined, but in most cases it is probably due to body dehydration . For further information on insectspiracular systems, see 5.3.1 . 8.6 TYPES OF P UPAE Pupae vary in appearance but have been grouped in two basic types; exarate and obtect. Coarctate are special exarate pupae with a puparium. For further information,see Peterson ( 1967) and Stehr ( 1987). 8.6.1 Exar'alc • most pupae are exarate • with appendages free or not glued to the body • with distinct and free antennae • with legs and wing cases held close to the body • look like mwnmified adults • non-articulated mandibles (adect icous) are common but rarely there are articulated mandibles (decticous), which cut through the cocoon; • all the Coleoptera pupae are of typical exarate type. The pupa 51 8.6.2 Coarctate (cxarate adeclilious) (wilh permisSIon/rom T he Rentokil Library. J/uflfue.1966) • essentially like exarate pupae, but remain covered by the hardened exuviae of the last larval instar • always adecticous • example: puparia of flies . 8.6.3 Oblecl 61"ith penmssion/rom The Hentokil Library, Jlunroe, 1966) • with appendages more or less glued to the body • the cuticle is often heavily sclerotized as in almost all Lepidoptera • the pupae of Lepidoptera (moths) may be covered by a silken larval cocoon • always adectitious (non-articulated mandibles). (u'lllI permlssi.on/rom The Hentokll Library, \/unroe, 1966) 8.6.4 SUIllIllC:l" Y of sa lic nt fcalu,'cs of pupae t) pes of solllc inscct onlc"s (all illUSlralions arefrom P elerson 1967, wilh permission) C()J,HOP1RR.1 (BHf.T/.f:) PI P-IE Beetle pupae are always adccticous (without functional man -dibles) and typ ically exarate (with free antennae, and legs a nd wing cases held close to the body). Pupae may develop in or on materials of the larval feeding site, in pupal cells or partially enclosed within the prepupa larvae exuviae, which are usually covered by hairy setae or spines for protection. Cerambycidae - Longhorncd beetle Scarabaeidae - Japanese beetlc Coccilleliidae - Ladybird beetle Lurculionidae - wee\'il 52 I-Ieritage Eaters LEPIDOPTERA (HOTHSAYD BC7'Tf~RFLlE,s) P[P1E The pupae are obtect pupae with mouthparts, legs and wing cases fused to the body wall. :\Jost pupae of moths are found in cocoons or pupal cells, both of which are made by the prepupal larvae. The cocoons are spun silk covered with bits of feeding material and the pupal cells are lined with silk. Adultsdissolve the silk for emergence. The butterfly pupa, called a chrysalid, is naked and attached to some object above ground. Jlolh (Heliolhis sp.) Butteifly (,.Vymplwlis sp.) DiPTERA PLPA/{I( H A \'D PLP1E These are basically adecticous (without functional mandibles) and typically exarate (with free antennae, and legs and wing cases held close to the body) but the pupa is inside a puparium, the sclerotized moult of the prepupal larva. VI!r'Lt"llt vent .. a.l llielopiidae (Btouifly) puparium and pupa inside HYMEYOPTERA PCPA£ The pupae are adecticous (without functional mandibles) and typically exarate (with free antennae, and legs and wing cases held close to the body), but have fairly conspicuous antennae. Apidae - HOfley bee (lawral and ventral view) Formicidae - ll-'ingiess worker ant The pupa BOX 8.1 SALlESI' FEATURES OF PUPAE OF SO,11E COJlfjlQX HERITAGE EATERS The characteristics selected are pertinent to problems of control in museums or homes. There is limited information and illustration of the heritage eaters' pupae in the literature, so the following material may seem incomplete. Sources used are ~ I allis (1982), :llonro (1966), :llosher (1969) and Peterson (1967). (from Koeller, 197J) (from LinsLey and MicheLbacher, 1943) EXAR.\TE PUPAE IVOOD BEETLES A llobium pUllc la lu m , common fUI'nitUl'c bee t le, \\oodwol'm • T he mature larva builds a pupal chamber close to the surface of the wood. • T he pupa is milky white when first formed but soon. darkens. • After rupturing the thin transparent pupal case the R. dul t remains in the pupal chamber until its exoskeleton has hardened. • The mature adult bores a flight hole about2mm in diameter for emergence from the pupal cha mber. Xes tobium rufovillosllm, d eathwat c h beet le Similar to A. punctalum, above. • Pupae are creamy wh ite and resemble the adult beetle in shape but the legs and antennae are held down (though not adhered to the body) by the thin, transparent pupal skin or case. • The mature larva enlarges a gallery immediately beneath the wood surface for a pupal chamber. • The adult bites its way out, forming a circular exit hole in the pupal case. Lyctus brllfifieus, pon del'post beetle • The mature larva fmishes feeding near the surface of the wood and builds a pupal chamber. • The pupa is first of all white but darkens before emergence. • The adult bores its way out of the wood, pushing sawdust (not frass with faecal pellets) in front of itself. STORED DRlED FOOD BEETLES S tegobium paniceum, drugsto r'e beetle • The mature larva builds a cocoon of food particles, cemented together with secretion from its mouth. Pupation occurs in feeding si!.e. Pupal stage lasts 12-18 days. • Adult bites its way out of the cocoon. 53 54 H eritage Eaters 80X 8.1 (COni.) SALIEXT FEATCR.ES OF PCPAE OF SO~\IE COJI \10 Y IlEJUTAGE EATERS (from ell/lief/den, 1911) (from Lins Lex and lfiche/bacher. 19.J)) ifrom LUHte) and thebe/blillter, 194)) \j;UI!l IIlllerhou ~(', 1991 Lasioderma serricorne, c ig a r'c tte bectle Pupation occurs in feeding site. Ten cbrio molit.or, m ealnOl'm Pupat ion occurs in feeding site. • The curved pupa lies on its side among foodstuffs. PlillllS sp. s pide l' bectl c • T he pupa is extremely delicate; it is first white then turns golden yellow. • The prepupal larva wanders to a hiding place and burrows in wooden walls or dense material and builds a spherical, thin-walled but Lough cocoon for pupation. • The adult remains in the pupal case for a few days then biles its way out. I/ IIJI,', F l Il .1 \ f) e lll PET BEE7VcS Oermesles macula/liS, hide bccLic • The last instar larva usually mon'S away from the feeding site to a pupation site. • The pupation site consists of SOllie compact material. The lanae make shorttunllels in any surfaces: wood , leather, softllleta ls, dripd meat, etc. • The naked pupa rests 111 diP tunnel plugg('d by the mature larva's skin. I fthe pupa ise'\pos('d on til(' surface the larva skill remains attached to the pupa. The pupa BOX 8.1 (COIlL) SALIEXT FEATUR ES OF P Li PAE OF SOJ4E COJ /J,IOY HERlTAGE EATERS (from Limley and jIichelbacher. 194J) A l.lagenus p el/io, fur beetle; A ttagenus meg alotna, blac k cal'pel bee tl e Pupae are never visible because they remain in last larva instar skin. • The adult may stay in the skin for 5-20 days. ,\ICSECJI A .YD CARPET BEETLES A nthrenus verbasc/~ varied cal'pet beetl c Pupation usually occurs in the feeding site. • The last larval skin is not shed hut remains and compietely covers the pupa. so the pupae are often mistaken for larvae. • The adult remains in thf' larval skin for 4-50 days. A fllhrenllsj1avipes, furnitul'e cal'pel beetle; A lllhrenlis museorl.lm , museum beetle Similar to Alllhrenus verbasci, above. A nlhrelltls scrophlilariae, common carpet beetle Pupation does not necessarily occur in the larval feeding site, but often found in crevices, e.g. in the 0001' beneath the infested material. • The adult remains in the pupal case for up to 18 days. OBTECT PL·P.I E CLOTllES .1fOTHS Tifleola bisselliella, webbing c lothes molh Prepupallarvae usually pupate hidden in cracks or folds in materia l in the feeding site. • The prepupal larva spins a cocoon of silk, smooth inside but with bits of textile or other materials from the feeding site. The length of pupation varies greatly depending on temperature and relative humidity. • The pupae are reddish-brown in colour and obtect, i.e. appendages adhere to the body. • On emergence the adult leaves the pupal case protruding slightly from the cocoon . 'I'ill ea p elliofl el/a, casemak ing clothes moth • The larva is always in a cocoon, which it drags around where\'er it goes. Incorporated into the silk cocoon are fragments of the material itis feeding on. • The pre pupal larva cocoon is used for pupation. \Yhen ready to pupate, the \arva seeks a protected placcaway from the feeding site, such as crevices on walls or ceilings. • T he cocoon is sealed at both ends prior to pupation. Trichophaga lapel::. ellll, tapes tl'), moth Sim ilar to Tinea pellionella, above. 55 56 H eritage Eaters REFEHENCES Agrel!, P.S. and 1\.:\1. Lundquist. 1973. Physiology and biochemical changes during insect development. In Physiology oj Insecta, Vol. 1. Ed. ;\lorris Rockstein. Academic Press, ~ew York, pp159-249. Chittenden, F.I-L 1911. Slored Food Pests. USDA Bulletin 8. Denlinger, D.L. and J. Zdarek. 1994. ;\Ietamorphosis behaviour in flics. Annual Review of EntomoLogy, 39:243-266. Gilbert, L.L and D.S. King. 1973. P hysiology of growth and development: endocrine aspects. In The Physiology of [n-secla, Vol. 1, Ed . . \ Iarris Hockstein. Academic Press, ~ew York, pp2S0-370. Cullan, P.J. and P.S. Cranston. 1995. 1'helllSects:An OutLineoJEntomol-ogy. Chapman and Hall, London, l'cw York. Koeller, G.K. 197:). Tratadode ta Prevision deiPapel yde ia Concervacion de Bibliotecasy Achivas. Servicio de Publicaciones del \ linisterio de Educacion y Cienca, \ Jadrid. Linsley, E.G. and A.E. \l ichelbacher. 1943. Tnsects affecting stored food products. California Agriculture Experimental Station Bulletin, i\"umber 676 \Tallis, A. 1982. Handboo!.: of Pest COlllrol, 6th Ed. Franzak and Foster Company, Cleveland, Ohio. \Iunro, J.W. 1966. Pests of Slored Products, The R entokil Library, IT ulchinson, VVest Sussex, CK. \losher, E. 1969. Lepidoptera Pupae. Five Collected If/arks Of! the Pupae of North America Lepidoptera. Entomological Reprint Specialists, East Lansing, \Iichigan. .'\ikan, T.B. and \T.V. Knole. 1989. I nseC! !3piracular Systems. Ellis Horwood, Chichester Peterson, A. 1967. Larvae of Insects, Parts I and 11. Printed for the author by E.dward Bros, Ann Arbor, ;Vlichigan. Stehr, F. VV . 1987.1mmalure Insects, Vol. I. Kendall/Hunt Publishing Co., Dubuguc, Iowa. Waterhouse, I) .F. 1991. The Insects of Australia. 2nd Ed The \Ielbourne University Press, \Ielbourne, Australia. 57 9 Nymphs and their Adults: Environmental Indicator Species SILVERF ISH, BOOKLlCE, COCK ROAC HES If insects from any of these three groups are found associated with heritage objects, they are foraging fo r food on the objects but have come from a warm , humid environment elsewhere. It is in that microenvironment that they lay their eggs and often tend the newborn nymphs. Because they indicate the presence of such an environment in another location, they are called environmental indicator species. 9.1 SILVERFISH A.\'O FIHEBRATS Order Thysanura ~ silve rfish , firebrats Salient features are: incomplete metamorphosis. nymphs like small adults. all stages cause damage with chewing mouth parts; nymphs wingless, flattened fish -shaped, less than lOmm long, long antennae directed forward , easily recognized by three tail -like cerci of equal length; the adult continues to grow and moult after becoming sexually mature. The pictorial key in Figure 9.1 illustrates these features. The cosmopolitan silverfish and firebrats are the common-est insect pests in homes and are prevalent in some museums and heritage buildings. Several COll1J1lon cosmopolitan species are shown in Figure 9.1. Therrnobia dorneslica is commonly called the firebrat be-cause it prefers hot (around 30°C), hwnid environments. Lepisrna. sa.ccharina. is called the silverfish because, when it moves, it has a side-sway reminiscent of a swimming fish, and because of its silver-colorned scales and fish-like structure. Silverfish prefer humid, warm (in the low200s)environments for egg laying. They move away rapidly from light and like to rest in tight, dusty cracks. They are thigmotactic, i. e. they like their bodies to make tight contact with surfaces. Silverfish and firebrats are indicators of the existence of a warm , hwnid environment, like warm heating ducts or water pipes in basements, kitchens and bathrooms, in which they have laid their eggs. Their presence at an eating site means a problem microenvironment somewhere else. They prefer to eat cerea ls, but these insects are a threat to heritage collections. They eat or graze on starch and protein sizing on books, documents, stored paper and wall paper. Pa -pers with lignin, i.e. newspaper, cardboard and brown paper, are usually not eaten. Silverfish and firebrats have starch -, cellulose-, fat- and protein-digesting enzymes and some have cellulose-di gesting bacteria in the ir digestive systems. They do not drink water but derive moisture from water vapour, moisture in materials and from molecular water in structural chemicals such as cellulose. The adults and nymphs are attracted to food because of its high moisture content. not its smell. The mouthparts of these insects are sim ilar to those of the cockroach and are used for biting off small pieces of food or scraping away surfaces. They may eat irregular holes in mounted paper or wallpaper to access the starch behind. Faeces, scales, irregularly eaten edges and often a yellowish stain are characteristics of silverfish and fire brat damage. I n the past chemical insecticides were commonly applied but today non -chemical control methods are used. The first approach is to eliminate the microenvironments the silverfish and firebrats prefer and the cracks and crevices in which they I ..,ta(' in tuft~ rolorbrown Thermobia domesficrJ FIREBRAT I wIthout 8et/ll oomb6 color slIver Lepisma saccharll/a COl-on·10N SILVERFISH I 2 pa,rs of styli culorgray , Sl'ta" ."ngl~ withM-tal comb!; I 3 palrsllf styh co lor brown ~( 'I' ".  ~CJS'''- (::: .. .. . Ctenoiepisma urbana GIANT SILVERFISH C~"oltpl$mo /OMBrcaudo of !lOm~ authors Ctenoil'plsma quadriSl'rlota FOUR·LJNJ:;O SILVf;RFISH Figure 9.1. Piclorial key lo species of silvelfish andfirebrals (from SCali, 1959, USD.J-IE .lV). 58 H eritage Eaters hide and rest. and remove potential food. I f the materials they attack cannot be secured in containers or cabinets, cut off their access by using an inert silica dust or diatomaceous earth around the bases or legs of cabinets. The dusts abrade the surface of the cuticle or adsorb wax, both of \yhich cause the insect to lose body water and dieof dehydration (:\ lallis, 1982). P revention is important. These insects are easily brought into museum buildings and hornes in boxes and packages, which should be inspected before being allowed inside. The adults are vulnerable to freezing and to temperatures above 40°C. Silverfish and firebrats can be monitored by using index cards covered with starch paste and placed in strategic posi-tions. T ypical damagc, as described abovc, to the cards will indicate their presence. For more information, see .\lallis (1983), .\!fodder (1975), Scott (n .d.) and Watson (1964,1967). 9.2 PSOCOPTERA - BOOKLICE Or'dc l' Psocoptcr'a - psocids, booklice Psocids are associated with damp, mouldy books, and are thus known as book lice. A booklouse is illustrated in Figure 9.2. Salient features are: incomplete metamorphosis, nymphs like small adults, length 1-2mm, soft-bodied; chewing mouthparts, all stages cause damage; characteristic long, thread-like antennae with from 13-50segments; body smooth, glistening, pale grey, without scales; wingless indoors; fast-moving insects that shun light. Psocids arc attracted to the mould on damp flour, meals and other cereal products, contaminating stored food with faecal pellets and causing some physical damage. They also feed on the moulds growing on starch paste, paper, wallpaper, etc., causing surface damage on paper by grazing the fungi. Thus psocids, like the silverfish, are indicator species of a microenvirollmental problem: past or present dampness. Indoors they lay their eggs in a warm (30°C), humid area and forage elsewhere. They require foraging temperatures between 9-ISoC and are killed by temperatmes around 37°C. Psocids can absorb water vapour through their soft, unpro-tected cuticle from air with relative humidity (HI-! ) as low as 58% (Knulle and Spadafora. 1969). Figure 9.2. COllanon booklotlse, Liposcclis sp. For fu rther information, see Ghani and Sweetman, 1951; .\ l allis, 1982; ~ew. 1971. 9.3 COCKHOAC HES 9.3.1 Order' Blattod ea - cockroaches Salient features are: incomplete metamorphosis, nymphs like small adults. all stages cause damage; flattened dorsoven -trally, chewing mouthparts, prothorax large and shield-like; usually four wings, when present the front pair is thickened and leathery and the back pair is membranous and folds beneath the front pair; legs adapted for running. The pictorial key in Figure 9.3 shows these features in some common adult cockroaches. Thereare many species, with very similar biology. 'rhe life cycle of the cockroach starts with the eggs, held in a special case called an ootheca which is carried, protruding from the posterior anal region, by the female. The female drops it when incubation of the eggs is complete; 30-40 nymphs emerge from the egg case, go through 6-7 instars and finally moult into sexually mature adults . The nymphs and adults are thigmotactic: they like to crawl into tight cracks where their backs and underside are in contact with other surfaces. They are active in the dark and find food by smell. The different species found around the world inhabit simi-lar envirollll1ents, preferring warm, moist environments in food preparation areas. bath rooms, garbage ducts, etc. These indoor microenvironments, with a combination of food, mois-ture and warmth, mimic the outdoor conditions of the cock-roach's evolutionary origins. Cockroaches are omnivorous, eating starchy, sweet food and meat. They are reported to have damaged heritage books, leather, parchment, wallpaper, natural history specimens, etc. They leave behind faecal pellets, and a characteristic odour called the 'attar of roaches', a combination of the odours of faeces, fluid from their abdominal scent glands, and a dark-coloured fluid they regurgitate from their mouths while eating. This latter nuid causes the stains in cockroach-damaged materials. It is often thought that cockroaches transmit human patho~ gens. There is no direct evidence for this, but a potential hazard does exist. 9.3.2 Pr'evention a nd l\ loni to r' ing To cont.rol cockroaches, their favoured microenvironments must be eliminated . If this is impossible, heritage objects in danger of bei ng attacked should be stored elsewhere . .l nsect-proof packages can also be used: clear plastic, refrigerator food quality containers with a tight seal, of all sizes and shapes, are commercially available (the plastic should be polyethylene or polypropylene). The critical thing is that the object must be dry when placed in the airtigh t container. Strang ( 1995) suggested including 1\11 monitoring paper strips such con-tainers and, if there is a problem, sachets of silica gel can be placed inside. Occasional cockroach occurrences do not necessarily indi -cate a problem because they migrate over long distances and \ ymphs and their adults: em'ironmental indicalOr species 59 GrRMAN CO()(ROACH (61Iftl"tI 9U"'t1"'CtI) I _SCOYf:~INGA'OVTNAl' Of •• 00IO£N ~"ON011M A'OI.IT I/.,NC".IOE A I SMOKY BAOWN COCKROACH (P,riplt1,,",,'uligi"tlst1) lA51SEG"E",TOf CEIICU$"'OTTWIC( .S lO"'G AS WJOE lA$TS(C>lOITO' C(IICU$ TWlt( AS lO"'G AS WIO E BROWN COCKROACH AMER ICAN COCKROACH (Puipltlll , '11 luuIIfI'(1) (P, riplllll"t1 1I",,,icII,,,,j '_O"'''O A&OI.IT 11. ''''e>< ''' 'OE WIT .. 'Al( 'O~O£~ ,_, WI"'O wIT~ OUT(~ I'Al(STII(A<.TUS( I'IIOHOT U" $TlUKI"GlT " ."U O AUSTAAUAN COCKR OAC H (P" ipltl" ,'t1 t1uSflt1It1, i ,,,) Figure 9J PiclOrial key 10 some common adull cockroaches (from Scoll, 1959, l 'SOIl.E. fl r;. may not stay where they are observed if food, warmth and moisture are not availablc. Por determining if there are cockroaches in a room, Olkowski el al. (1991) suggested that homemade traps are just as effecti\'e as commercial ones. They describe preparing a trap with a wide-mouthed 500ml jam jar. baited with a small piece of white bread place.d in the bottom and its inside rim covcred w ith petroleum jelly . T he jar is placed at th e site of the problem. in a warm , humid, dark spot. J f cockroaches are caught the top can then be screwed on and the jar placed in the freezer for a day or two to kill the cockroaches. 9.3.3 Dea ling" ith Com mcl'c ia l Pest Eradicatol's A building infested with cockroaches is a problem for a commercial insect pest eradicator. Obtain a reference from the company and explain the precious nature of your collec-tion or heritage objects . .\Jake sure that all chemical products used are documented by data sheets as to health hazards, flammability, chem ical reactions. etc. This information is always available from the product manufacturer. T here are three points to evaluate the product: the health hazard, t he hazard to the object and the effectiveness against the target insect. For further information on cockroaches, see ~lallis (1982), Olkowski el al. ( 199 1) and Scott (n.d.). llEFEllE'(CES Ghani . .\1..\. and Sweetman. II.L. 1951. Ecological studies of the book louse '"lj)Osee/is dlt'inatorius ( .\ Iull. ), Ecology, 32:230-24+. "-nulie, W. and H.H. Spadafora. 1969. \Yater vapor sorption and humidity relationships in Liposce/is ( Insects: Psocoptera). Journal of Stored Products Research, 5:49-55. Lasker. R. 1959. Cellulose digesting insects. In .Harine Boring and Foulifl{[Organisllls, Ed. D .L. Ra). University of \\ ashington Press, Seattle, Washington. pp348-358. .\Iallis, .\. 1982. Handbook of Pest Control. Be/wriou,.. Life history. alld Confrol off fousehold Pests. 6th E.d. F ranzak and Foster Company. Cleveland, Ohio .\Iodder. \Y. \Y. 1975. Feeding and growth ofAcrotelsa collaris(Fabr icius) ( Thysanllra, Lepismatidae) on different types of paper. Journal oj Stored Products Research, 11:71-74. ~ew , T.R. 1971. ,-\n introduction to the natural history of British Psocoptera. The Entomolo{{ist, February-.\pril. 59-96. Olkowski , \Y., S. Daar and II . Olkowski . 1991. Commol/·Sense Pes! ('ontrol. The Taunton Press. ~e\\'LOwll, Connecticut. Srotl. H.G, n.d. Household and Slored· Food lnsecls of Public H ealth importance and TheIr COlllrol. L'.S. Department of Public ll ealth. Education a nd We\fare, .\ t\anta. Georgia. Strang. T.J.IZ. 19S5. The effects of thermal control of insects. ]rd Internatiollal COIiferellce all Biodeterioratioll of Cuiwral Property. Julx 4--7. Bangkok Thailand. pp 199- 212. \Yatson, L\.1.. 1964 . .\ Ioulting and reproduction in the adult firebrat. 'lhennobia dOillestiul (Packard) (Thxsallllra, Lepismatidae). 1. The moulLingcycleand its control. JOUl7laloj[IIsect P/~) 'sio'ogy, 10:305-317. \Yatson , J . .\,I .. 1967. Reprodu ction. fceding acti\·ity. and growth in the adult firebrat, Lepismodes inquilillus (~ewman) (Thysallura. Lepismatidae). JournaL of Insect PhysioLogy 13: 1689- 1698. 61 10 The Adult: Trapping and Monitoring 10.1 T II EA DULTS to.1.1 Introd uc tio n 1n trapping adults in heritage collections the common insects thatarca concern are moths and beetles. \Yesee the adults only on traps and, occasionally, a flying moth . Adults arc rarely found in infestations. Books on the control of insects in museums all have excel-lent illustrations of the adults. The identification of all the adult insects that are found in museums would form a book in itself. T his chapter will discuss only the biology of the adults that is pertinent to trapping and monitoring, i.e. light re-sponses for light traps. sex odour attraction for pheromone traps and feed ing site odour for oviposition sites. The general morphology of some common beetle and moth heritage eaters is shown in Figure 10.1. Figure 10.2, a pictorial key tosome common beetles and weevils, includes stored grain and food product pests. T he role of the adults is reproduction: rarely do they eat. The insect pests have a variety of patterns as to when and where the females mate. Some mate as soon as they emerge and lay eggs in the feeding site. Some females move away from the site and the male flies to the female, either at night or during the day, and they mate away from the feeding site. The female then must find an oviposition site for egg laying with a new potential feeding site for the new generation. Some adult insects fly to flowers for a pollen ffil'll l before or after mating. T o cover all the variables there are three main methods of trapping, based on insect physiology: iight responses for light traps, sex odour attraction for pheromone traps and feeding site odour attraction for oviposition sites. T he traps are made up of the attractant - light, pheromone or food -and a method of catching the gullible insect, such as a sticky landing surface, water or electricity. 10.1.2 Reasons for tra pp ing insec ts Capturing, trapping and other sampling mf>thods of insect populations in the field have been used for the basic studies of insect biology: population dynamics, ecology and behaviour in nature. The greatest th rust in trapping technology has come from appli ed entomology, i.e. the study of agriculture and forest insect pests, of stored food insect pests and medical entomology. According to the species of insect involved and the nature of the investigation. many different sam pling methods and designs of traps have evolved, and trapping systems are being rev ised constantly. Against this continually Anthrenus verbasci (L.). varied carpel beelle. Anthrenus scrophulariae (L .), common carpel beetle. .\ ttagenus pellio (L .), black carpel beetle. LycLUS brunneus (Steph.), brown pou/derposl beetle. Anobium punctatum (De Geer), commonjurniture beetle. T inneola bisselliella (Humme!), webbing clothes moth Figure 10.1. General morphology of some common adult heritage eaters (Royal British Columbia Wuseum, by Ann flou-oll · Kralm). 62 Heritage Eaters HIOMIIU" WITH & l[["lHOHEACH SlOE B[.~ A!5(IjT,SP£t t(S AeouT 118 ... eH LONG PIIOHOTI,tWWITHOUT THT" 01< f.cH StO/: PRO/'OOru .. WIH<OUTl"[['T><ON[~"SIOE 8[A. "~ESEN T. SPEC'ES ABOUT 118 I ... e ... LONG BEUlSSEHI I S:'~~:O:;"~i ~;~:",,!~~E I S"' ..... l8RO •• LSH SPECL[S l£SS'MAHLIA INC"LONG UII(,(~BLJ"'SHSP£CI ES II. TO llO ' ''' .. !..ONe I Ht·DVIS I8Lf~_.BOVE "B'''CHl,.I)I.h..OI'IMOI'IE ro.<!EWlIOGWITHLtHCOSUllr.ocE I I H[IoDHIOOE .. uL~F>IIONOTU" USSl> .... 118 1HCHLONG ~ I FORE WI..aW"" UHE,) ~ ' LAnCN(06E[rLES c=~T~E;l~~~~~T:~~s COWV(KBHTl[S 1/2 1HChl.ON1;OIIUOf1E PRQNOtu .. "O',\oSIROHG<,.y !;£PAIIAT[O'_8A!olSOF""N(,S Figure 10.2. Pictorial key to some common bee lIes and /ren 'ils (Scott, n.d., Cs. Dept Public /-Iealth Services) changing background it is inappropriate to offer firm instruc-tions for all circumstances. \lethods developed for a specific species in a specific envirorunentare very often unsuitable for the same species or a closely related one in another environment. In the museum world and in our homes we have t ransferred this technology to our own insect pest problems. We must. however: question whether the useofthese techniques is helping us obtain our goal of prevention of insect pest damage or whether we doing things without knowledge of their full consequences. I n the food warehousing industry, trapping insects is used for monitoring and sometimes for eradication or population size control. Thegoal is reduction of product loss, not complete elimination of loss. In forestry and agriculture trapping is carried out not only to determine insect activity but also population size and the sexual maturity of individuals. This information is used to determine when best to release insecti -cides or biological organisms (parasites, disease organisms) for population control. [n the heritage collection, the value in monitoring insect activity is determin ing if there is a problem and also the location of the problem. The next and most im portant step is inspection of the collection, in order to locate the infestation, the source of the insects tha t were trapped . Jnspection of collections of her itage objects is the most important aspect of an integrated insect pest control programme. Thecommon types of insect traps are li ght traps , pheromone traps and food traps. 10.2 LIGHT Til IPS 10.2.1 Light r esponse of insec ts Lighl traps have been used as attractants, based on food -seeking responses. e.g. colourofOowers, UV radiation of sunlit spaces, low light intensity fo r moonlight Oyers, etc. The trap includes a light source, and a method of capturing the insect once it has been attracted there. The insect's reaction to light results in phototaxic behav-iour, i.e. a body orientation to the light. The reactions are dependent on the light intensity, brightness, and wavelength content and on the insect's colour vision (spectral efficiency of the photopigments of the insect eye) , and the insect's develop-mental stage. The larval stemm a is like a basic unit of the adult's ommatidium and compound eye (Figure 10.3). They ~'".''''''' tryst.lI ,n'con, . .t or,m.'V pigm'n~ c,1I cornUg,ncusc,1I ,oJ ~ . U-::,::,~~'" IL,~oo,,~ ,om,., '''' ~_""m'.' m,m.,., Figure 10.J. Long illldirla/ sections lhrough the simpLe and compound eyes: (a) a simple Slemma of a Lepidopteran larva; (b) dorsal ocellus of a aduLl hug; (c) an ommatidiumJrom a compound eye, Il'ilh enlargement sho/liing a transverse section. (From Gullan llnd Crllnston, 1994, lI'ilh permission) The adult: trapping and mOllilOrLng 63 both have lenses. light-gathering pigments and neurons for transmission of the stimuli. The ability to resolve an image depends on the number of omlnatidia in the eye: the silverfish has around 12, whereas the dragonny has] 0.000. The ocelli and stemmata do not resolve images: they most probably detect only sudden changes in overall illumination. Colour vision or wavelength discrimination means the ability to distinguish between spectral lights of different wavelengths independently of intensity. The spectral sensit iv-ity of an insect's eye depends on the absorp tion of light of specific wavelengths in the photopigments. Early experiments in behavioural studies gave variable results but suggested differences in insect colour vision: for example, they showed that the Papilio butterny prefers purple and blue colours, whereas aphids and Vanessa butterflies prefer yeLlow colours. The presence of photopigments was dem-onstrated in the early 1960s. Since that time experiments dealing with individual ommatidia cells in the insect eye have revealed that they vary in responses to colour, or light wavelength. Long wavelengths of light, 350 to 650nm, are visible to most insects, but there are peaks of sensitivity, which arc due to types of ommatidia or receptors. The colour receptor types in the insect eye can be divided into three large groups: U\7, blue and green receptors. of which the mean maximum sensiti\'ities are around 350nm, 440nm and 510nm respec-tively . . \ Iost insects show two colour sensitivity peaks. rn cock-roaches, Bla/Laria and PeriplaneLa, the sensitivity is over the range 365 to 507nll1 with two peaks, UY and green C\lote and Goldsmith, 1970). Figure lOA shows that the ommatidia of the drone bee can distinguish three groups of colours (Burkhardt, 1977). :\ l oths show l1V and possible blue and green-yellow receptors and beetiesshov., UV and green-yellow receptors. Flies have an infrared receptor along with UV and blue receptors (Blum, 1985). '\ lost insects visualize UV in the range 300-400~ . Gener-ally, UV light is most attractive to insects under natural conditions, leading to the success of trapping insects in the field using a U\T_ emitting 'black lamp' . The attraction to UV is possibly due to the resemblance of the light to open spaces l00r--;~--------~----~~--------------. ~ § 50 ~ I 01"". Ult. a" ole! YeUow- ' ~g (1'1 grel'n \\7avelength Figure 10.4. Visual cells ~ the drone bee, stimulated Il'ith light oj different lI'u/lclengths shOll' three receptor types u:ith nw,l'imum spectral response: A ~ at J60 nm (Cf/ receptors): B - betu;een 420-460 nm (blue receptors); and C - at 530/lm (green receptors) (from Burkhardt, 1977). 1.1 DiSiance from lamp (em) Ibl ,~ ,'5 20 is Distance from ramp (cm) '" Distance from lamp (em] Figure 10.5. Radial density distribution oj three species ~ mOlh~ on baffles round light trap (from lfuir/tead- Thomson. 1991). in nature, which reflect UV light when nooded with sunlight. UV light traps are more effecti\'e than incandescent light traps for food storage beetles. Besides wavelength, light intensity may also be involved. For example, below levels of 5-1 0 lux, diurnal (active during dayl ight) species have monochromatic vision (as humans do at tw ilight). The nocturnal species become colour-blind at light intensities 0.5-5 lux (moonlight is around 0.21ux and a moonless night 0.0003 lux). lnsects do not always fly to the brightest light but show preferences for specific colours. The structure of the moth's eye is developed for ma.ximum sensit.ivity and adaptation to the dark and the beetle is adapted for bright light. ;\ l uirhead-Thomson (1991) showed that moths did not tend to be trapped immediately arOund light, but the maximum number o'apped were at a distance of 40cm from the light source (Figw'e 10.5). T his may be a response to light intensity. Hsiao (1972) showed that at low light intensities moths displayed positive phototaxic behaviour but at high intensities showed negative phototaxic response near the light source; they did, however, land at a peripheral dark margin of the Light. This led to an improvement in trap design: simply painting the light baffles black. 64 I-Jerilage Ealers For further information on insect light response,see Gullan and Cranston (1995), :\lazokhin-Porshnyakov ( 1969), ;'\Ienzel ( 1979) and Scobie (1992). 10.2.2 Light l..ap design a nd placement Taking advantage of insects' specific attraction to light, we have designed effective light traps. Insect traps were first used outdoors, in nature, to collect insects for entomological and ecological studies. Outdoor light traps have very little real value for museums, but an exception is the use of a light trap outdoors to counteract a building light also acting as a light trap. Because so many of the insect. pests that invade our heritage collections come from outdoors, some care must be taken to prevent them from coming inside. Outdoor night lighting of a building may attract these inscct pests to the building. Gilbert (1984) suggests that a light trap that emits more UV than the building lights , placed 45-60m (ISO-200ft) away from the building will attract insects away from the building lights. The commonest outdoor light trap is the insect electrocutor type. The design of commercial indoor traps varies. They are constructed usually for specific target insects. The light bulbs used in commercial light traps are usually blacklight bulbs (Gilbert, 1984), which emitasmall amountofUVlight, which is shown to attract most flying insects. There are many com-mercially available bulbs with an inside phosphorus coating, which is required to release the UV light. The placement of the trap is critical , while the distance from the sedentary insect to the light is also important. The distance from which the light trap will attract the insect is dependent on the lamp type, the trap design and the visual acuity and nature of the target insect. Gilbert (1984) reported that most flying insects cannot respond to light from further away than 30m (100ft), and they respond at 6-7.501 (20-25ft) and more significantly at 3.5m (12ft). Placing traps about 15m (50ft) a part is the general rule in a warehouse, but this is only a broad rule because there are so many variables involved. The placement of the light trap at a specific height above the floor may be significant (Keever and Cline, 1983). For day-flying flies , Gilbert (1984) suggests that, because of the sur-face -skimming flying behaviour of day-flying insects, t he most effective traps are placed near the floor. } Jost night-flying insects fly at greater heights but exceptions are grav id female moths, which are not strong fli ers and are captured close tooron the floor. At the Royal British Columbia Museum (Florian, 1987) female webbing clothes moths '.vere captured close to the floor and males at a height of 1.2- 1.5m (4-5ft). Keever and Cline (1983) reported that at 1.8 and 3.7m (6 and 12ft) above the floor there was no difference in the sex of moths captured. Light traps can be strategically placed in bottlenecks. stair-wells and corners of large storage facilities. The insects caught in the light trap should be removed immediately and the insect numbers and species recorded on a computer database. This will collate information about the influx of new species or an abnormal increase in the numbers of one species, which could point to a specific problem related to the storage of the heritage collection. Tn the pest control literature there is some pertinent infor-mation that will assist in designing light traps for particular insects. In :\.l allis (1982), besides useful data on moths and carpet beetles, the bibliography is extensive and cites many references on specific insects. 10.2.3 Lighll r'a ps - summary The most effective light for attracting flying insects is UV light in the range 300- 400nm. High-intensity incandescent light repels night-flying insects; low- intensity light attracts them. ;\1oths show UV and possibly blue and green-yellow receptors and beetles UV and green-yellow receptors. Flies have an infrared receptor along with UV and blue receptors. The main value of light traps is that they can capture both sexes of a variety of species. The placement and design of traps should be adapted to the target insect. There is a limit to the distance for efficacy of the light trap. 10.2.4 Review of the lile r'a lur'e on use of lighl traps in he ritage collections Light traps are recommended ror use in insect pest monitoring in museums or other buildings where there are heritage objects. The most important fact impacting on your activities in purchasing or making insect light traps is that you do not know which insect species you are try ing to catch. You will not know Wltil you catch some, and even then you will not know if you have missed some that have not been attracted to the type of trap you have used. Thus, a variety of traps is the most logical approach. It is worth testing different colours of incandes-cent bulbs associated with different colours of sticky traps. Vary-ing light intensity and height from the floor should also be tested. There is very litt le definitive information about the light responses of common insect pests in museums butsome results using ligh t traps are reported by Gilbert ( 1984). Those at-tracted to light were the black carpet beetle, the cigarette beetle (Lasiodelmaserricorne), the drugstore beetle (Slegobl:um paniceum.), reproductive winged termites and the house fly, but booklice and silverfish were not attracted to light. Cock-roaches, pill bugs and ants are commonly found on light traps because they are foraging for other insects and smell them on the traps. This is another reason for removing insects as soon as they are captured. Florian (1987) reported that the carpet beetle (Reesa vespulae), the varied carpet beetle (Anthrenus verbasci) and the house f1y are attracted to windows and the webbing clothes moth (Tineola bisselliella) to diffusely lit yellow sticky traps. At the Royal British Columbia lVluseum (Florian, 1987), tests were run in all col lection areas, using sticky yellow strips, 90 X 10cm (3ft X 4in), installed hanging from every red exit light or small squares cut to fit behind blue, 4 VV n ightlights that plug directly into the electrical outlet at baseboard level. The sticky strips, which are universally available, are made of yellow plastic coated with a tacky polyethylene glue. Gooseneck lamps with the sticky tape hanging from them were successful in capturing beetles. All the traps were professionally labelled showing they were put in place by the Conservation Section. These small traps could be placed anywhere in the collection The adult: trapping and monitoring 65 Table 10.1. Distribution o/the varied carpel beelLe (:\nthrenus \'erbasci [ L .) by Iril/dou's al/d/loon o/the Royal Brit ish Columbia _~ /useum. Results ofsun'ey 0/ \/ay 5 to Sept. 20, 1986. FLOOR 2M 3M 4M 5M 6M 7M TOTAL W INDOW I 4 0 4 3 5 18 6 14 7 5 8 I 9 6 10 17 II I 12 6 13 0 14 0 15 4 . 16 0 17 I 18 0 19 I 20 7 2 1 I 22 8 23 9 24 2 25 4 26 5 27 0 28 I 4 TOTAL 17 10 21 27 12 1-7M represent the noor numbers, 1-28 are the window numbers on each floor window by window (1-5 east-facing windows. 9-19 south.facing windows, 20---28 west. facing windows). area, their close proximity to potential insect captives making them more efficient. A variety ofl ight traps were tested in museums by Zaitseva ( 1991). It was determined that electrocution light traps were not successful but that traps using luminescent bulbs, filament bulbs and bulbs of DPC·50-1 specification could be used. The traps captured a large variety of insects from the families Dermestidae, Anobiidae, Latridiidae, Tenebrionidae, Tineidae and Floridae. All open-type container with a DPC·50· 1 bulb attracted a large number of clothes moths. J t was also reported that the windows in the building were successful light traps. In forestry research (to monitor and study biodiversity of insects), a portable light trap is used. It is operated on a 6V battery or AC current (110V), and uses very small 1.8\\' light tubes. I t hangs likea lantern and captures the insectsin various ways in a container below the light. Besides the UV light tubes, there are light tubes available in blue, green and white light (Jobin and Coulombe, 1992). This seems like a sensible light trap for museums. 10.2.5 Case stu dy - use ofwi ndo\\ s as light tmps Often the best light traps are windows, though they arc limited to daylight-flying insects. At the Ho)'al British Columbia ~Juseum , the large bank of windows on each floor of the Collection Building were used for light monitoring of insects (Florian , 1987). A computer data· base was used to record all insects collected, each week, on the window sil ls. The information has been useful in determining emergence patterns and new infestations. Other insects that do not infest the collection were also collected. The final results showed that there was an endemic population of interacting insects, combined with minor environmental problems. The procedures involve numbering all the windows on a floor plan and recording information for each window. Table 10.1 shows the distribution of the varied carpet beetle (Alllhrellus verbasci) and Tables 10.2- 10.4 the distribution of the common house fly (tl1usca dom.eslica), according to win· dow and floor, over a period of three months. Table 10.1 shows two distinct populations which were located in the areas where active infestations had been found. The one on the 3rd floor (windows 4-7) was very localized and the one at floors 6/ 6,\J (windows 5-8) was more diffuse, which suggests that it was apopulation that may have been active for a longer period and had spread out. These two populations were located on the southeast windows. The diffuse distribu-tion on nearly all the floors by the southwest windows sug· gested a building problem. Th is type of da ta representation gives an excellent insight into insect populations. This information led to an intensive inspection or the collections in the areas of highest concentration. Active infes· tations were located on floor 6:\1 in an archaeological com-parative faunal collection of seal skulls and on the 3rd floor in skeletal collections of small mammals. T ables 10.2-10.4 show the distribution of house flies . They were found mainly on 7,\1, the highest floor, which suggested a building problem . An external examination of the building in this west corner showed that there was a small open seam 66 rierilage Eaters Table 10.2. Distribution of the common housefly (\ I usca domestica [LJ) by Il'indou:s and floors of the Royal British Columbia J\lusewn. R esults oj survey if 26 January 1987. FLOOR WINDOW I 2 3 4 5 6 7 8 9 10 I I 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 2M 3M 4M 5M 6M 7M 26 17 28 1- 7M represent the floor numbers. 1- 28 are the window numbers on each floor window by window ( 1- 5 east-facing windows. 9-19 south-facing windows, 20---28 west-facing windows). Table lOJ Distribution a/lhe common housefly (.\ Iusca domestica fL.}) by Irindoll's alldfloors of the Royal British Columbia lIuseum. Results oj survey 0/2-6 February 1987. FLOOR WINDOW I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 2M 3M 4M 5M 6M 7M 1- 7M represent the floor numbers, 1- 28 are the window numbers on each floor window by window ( 1- 5 east-facing windows, 9- 19 south-facing windows, 20---28 west-facing windows). The adu lt: lrappill{! and m on itorin{! 67 Table / 0. 4. DI.~lnbullo" of the common housefll · (\ Iusca dOIll('stica f L L b.l II" lIldOIl"S andfloors of the R o.\ al Brrt ish Colum bia \/useum_ Results of sun.·e) of /6-20 l/arch 1987. FLOOR WINDOW I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 2M 3M 4M 5M 6M 7M 1-7M represent the floor numbers, 1- 28 are the window numbers on each floor window by window (1-5 east-facing windows, 9-19 south-facing windows. 20-28 west-facing windows). between the last west window fram e and the ceme nt facad e all the way up the building. This corner of the building is also the area catching the late afternoon sunlight. Both would seem to attract house flies. The flies were not pupating in the building or on the roof. The decreasing size of the population over the winter months suggested that they were coming from outside. In the areas of the highest concentration , the plastic protectors over the banks of recessed lights w~re cleaned , but only a few flies ,,·ere collected. It still has not been determined ho,,· the flies were getting into the building but the main concern was that they are ovipositor sites for carpet beetles: live carpet beetle larvae have frequently been found in the abdomen of house flies. Because of this it is imperati\-e that all flies are col lected on one day each week and frozen as soon as collected. There was no evidence that the insects came in with the air supply. There are two air filters , the finest operative down to the micron level. Tests with cotton cheesecloth placed over the air vents did not capture flies over a period of I month , and at the same time 10+ flies appeared on the windows. 10.2.6 l s ing inro r-m a l ion rr-o lll t l'a ps The information from light traps tells more about the popula-tion in your museum or collection area than any published literature. The information gathered over the years shows the annual fluctuation in population size of a specific species. There is a normal increase in population size due to the arrival of the adults freshly emerged from the pupae. Even though this occurs inside an air -conditioned building, it still seems to coincide with spring (:\ larch), but often a little earlier than it occurs outdoors. An abnormally high number of captured insects would alert you to a new infestation or some environ -mental problem. _\n example of this occurred at the Royal British Columbia :\]useum (see 2.5.2.3). O\'er one Christmas period. because so many staff were away on holiday. the floor maintenance crew decided to strip the floor on 12 floors and rewax them. This process caused a humidity increase in the building which was obvious on the hygrothermograph charts but was not significant enough to be considered a problem and was easily stabilized by the air-conditioning system. But \\ ithin 12-14 days after the humid-ity increase there was an increase in the number. higher than previous years for this time_ of captured adult \-aried carpet beetles. From the literature we know that for this insect 12- 14 days is the length of time that adult emergence would occur under conducive environmental conditions. Thus emergence must have occurred because of the high humidity resulting from the water used during the floor cleaning. Organic mate-nals will adsorb moisture readily if the temperature is con -stant and the RH increases. One feature of organic materials is their opportUl.ism: they take up moisture rapidly but give it up slowly. T he rise in moisture in the pupae and in the adjacent organic materials must ha\-e triggered emergence. A second increase in the insect population occurred at the same time as in previous years but there were fewer indi\-iduals caught. T he appropriate response to the unexpected increase in population was to increase the number of sticky light traps in 68 I-ferilage Eaters collection areas to determine if the insects were concentrated in one area and associated with an active infestation, and to carry out some inspection of the collection to ensure that the objects were protected from the flying adults. Hemember that it is the heritageobjccls that are the food traps, the odour of the organic material of the objects that is the bait. Dense plastic boxes arc impermeable to most odours, as are specially constructed biaxial plastic and plastic/ alwninium foil laminate bags. 10.3 LU lliNG Til E SEXES 10.3.1 Intl"oduc ti o n Insects rely on their sense of smell for many of their behav-iOlll"al patterns, e.g finding food, choice of site for laying eggs (oviposition site), male selection and finding, courtsh ip. social activities, alarm signals, etc. The chemicals produced and emitted by individuals that cause other individuals to va ry their behaviour are called semiochemicals. There are three categories: allomones, defence secretions that repel predator species; kairomones, which attract predator species; and pheromones, sex attractants. Synchronization of the sexual maturity of partners in any type of bisexual reproduction and the production of scents or pheromones, i.e. sex pheromones and aggregate pheromones are essential for reproducti\'e success. The use of odours to attract insects to traps is based on these behav-ioural responses. Pheromones are volatile, odiferous chemicals that are se-creted by insects as a part of the communication system directing their behaviour. :\ lost pheromones are sex attract-ants but there are others that inOuence behavioural patterns between the same species: alarm signals, trail marking, aggre-gation, social activities and predator attraction between dif-ferent species. Thus, in nature, species-specific pheromones bring the sexes together but they may also attract predators of these insects. For stored food insect pest species (Burkholder, 1984) in which the adults are short-lived and do not feed (moths, dermestids, bruchids and anobiids), the female produces the pheromones attracting the male. For the long-Ii\'ed adults of the flour and grain beetles, a long-range aggregation pheromone is produced by the male, which attracts both sexes. The pheromone for the black carpet beetle, Allagenus megaloma, was identified in 1967 and since then pheromones for nearly all the major insect pest species have been identified and most synthesized (Burkholder and :\ la , 1985). 10.3.2 Commc l'c ia l phe l'omone traps fOl' fOI'csts, orehar'ds a nd crops, a nd " a l'chouscs The use of sex pheromones in attracting and capturing insect pests originates in agriculture, forestry and food product ware-housing, in which large populations ofinseet pests need to be con trolled or assessed. Commercially available traps vary in construction and design but all contain synthetic sex pheromone lures incorporated with various controlled release mechanisms. The insects are usually captured on sticky traps, or crawl or are sucked through funnels into oil or some other liquid at the bottom of the trap. Pheromone traps are sometimes combined with food bait or light. Outdoor pheromone traps have been developed for forest and crop protection as an alternative to chemical pesticides where pest resistance was a problem and in consideration of environmental issues. The traps are generally used as monitor-ing systems to determine: the presence, seasonal emergence patterns (start. peak and termination of the flight period) and density of a population. This monitoring is integrated with other control approaches, to determine when is the best time to use chemical pesticides or to release predator insects (bio-logical control) tocontrol the target insect. \\'hen used with an insecticide, follow-up monitoring assists in determining the success of the chemical treatment. Indoor pheromone traps for flying and crawling insect pest control have also been developed for food product warehouses. The main purpose of these traps is for population control, which is achieved by monitoring to determine where active infestations occur, by capturing some insects to reduce the population size and by selectively trapping one sex to reduce rnating possibiliLies or to cause mating disruption. Thus these traps do not eliminate the population but only give information about the infestation and achieve minimal population reduction. :\ Iass trapping wilh pheromone traps has been used for insect control. This involves placing a large numberoftraps in a small area with the aim of eliminating the population. \\'hen pheromone traps are used in a building there are potential problems. :\ lost of the insect pests in bui ldings have been found in large numbers outdoors, so the indoor traps could attract these insects from outside into the storage area. In warehouses this is partially prevented by placing the traps away from outside openings. Another problem is the attraction of insects that prey on or are scavengers of the target insect. It is also important to remember that the traps may be specifiC to one sex or to only those adults in a specific hormonal developmental stale and that the larvae are still causing damage. :\ Iass trapping by flooding the area with pheromone traps has been used in granaries, but the possibility has been men-tioned of product contamination by the attractant pheromone in the product, thereby rendering the product prone to subse-quent infestations (Burkholder and .\la, 1985). For further information on commercial pheromone traps, see Burkholder (1984), Burkholder and ~Ia (1985), ~'l cVeigh ct al. (1993) and ~ I ueller (1982). 10.5.3 T hc c he mica l na tul'c of phc romones In discussing the use of pheromones against stored food insect pests, Burkholder (1984) categorized the main groups as: togodermal isomers, megatomoic acid isomers, dominicalure, sitophilure, tetradecadienoicacid (TDA) and serricornjn, which were the major pheromones avai lable at the time of publication. The chemical characteristics of these substances are: fat solubil-ity, deterioration susceptibility (oxidation, etc.) and volatility. This information is necessary because we need to know how long they are effective, theirshelflife, and whether or not they can be absorbed into artifact materials such as oily skins, fur, leather, cellulosics, plastics (polyethylene), etc. The adult: lrappl:ng and monitoring 69 A true story: a forest entomologist worked for years on pheromone traps for the gypsy moth, so now when in the field the entomologist is the greatest pheromone tra p. The pheromone has dissolved in his body fat and the moths just lo\"e him! 10.3.4 Us ing phcl'Olllone tra ps in buildin gs " ilh he"itagc collections Pheromone traps are commercially a\'ailablc against the fol-lowing insects commonly found in museums or other build -ings with heritage collections: common house fly (JJusca domeslica), German cockroach (Blaltella germani~n), ware-house and khapra beetles (Trogoderma spp.), furniturc wood -worm (Anobium punclatum. webbing clothes moth Tifleola bisselliella), drugstore beetle (Slegobiwn paniceum, cigarette beetle (Lasiodenna serricorne) and I ndian meal moth Plodia inlerpunclella C\lueller, 1995). Phero mone traps against the varied carpet beetle (Alllhrenus verbasci) are now being developed. Pheromone traps have been suggested for use in museums by Child el al. ( 1994), Gilberg, 1992, Gilberg and Roach , 1991; Javovich , 1987; Kronkright, 1991. ,\luseums, however, havc little experience with these traps and they ha\"e often been brought into use without thought to the necessary research required before they can be safely recommended. Just because the trap attracts a specific insect is not enough. 10.3.5 J\lonitOl'ing the va lue of phe"omon e traps Pheromone traps do not achieve elimination of the popula-tion, which is essential when dealing wi th the protection of heritage artifacts. The value of pheromone traps is in detecting and monitor-ing insects and locating active infestations. Constant monitor-ing of the population gives information about the time of emergence of adults and variations in the size of popula-tion. If there is a sudden or untimely change in the number of insects trapped, this suggests a problem. To locatc the source of the insects, traps can be placed around an area of original insect capture, repeated in a smaller area and so on, to zero in on a specific area of the greatcst insect activity which would then be visually inspectcd to locate the infes-tation. The use of a great number of traps in the hope of elimi -nating the population is not appropriate beca use only indi-viduals of one sex and in a specific physiological state are attracted. 10.3.6 Bc fol'c use, considc r ca re full y what the phe romone ll'a ps do Attracting insect species that are not already in storage areas can be a problem. For example, the traps can attract a species ofinsecLS that prey on the target insect. \ l ost buildingscolltain an endemic population ofinsecLS that interact with each other and are not necessarily in storage areas. The traps placed near heritage collections may expose the collections to potential extra infestation. Beetles and moths living in a natural history skeletal collection, for instance, may be attracted to a pheromone trap set in a collection of histori cal textiles or garments. 10.3.7 Is the spec ies ~ou a l'C tar'geting the cu lp"i t? Another disad\'antage to the use of pheromones in the mu -seum is that there may be many different species that could be overlooked if such a species-specific trap were used. In the museum or storage area there is usually a mixed population of endemic species. 1 t is important to know all the species present, so species-specific traps are notefficienL They may have their use if, for example, all other methods of trapping are not showing an insect that you know is present. Speci fic pheromone traps would then be logical for this :::pecies but must be used with knowledge and prudence. 10.5.8 Tra p ('csults may be mis leadi ng The interpretation of the insects trapped is important. It requires an understanding of the beha\"iour of the target insect and the type and effectivcness of the trap. The main value emerges in monitoring the target insect population over time to determine if there has been a change. Because you have not caught any insects with the traps does not mean you do not have a problem. The problem may be with another species not targeted with the pheromone used. Also, there may be few insects in a reproductive state that would respond to the sex attractants, or there could be an imbalanced number of the specific sex being attracted. Re-member that the pheromones most commonly used are those that attract only one sex. 10.5.9 Il avc the hCI' itage objccts becomc scx atll'ac ta nts? \Ye do not know if the heritage objects made of organic materials adsorb enough pheromone to be a potential attract-ant to insect pests. This is a question that should be answered before pheromone traps can be used in museums and heritage buildings. The heritage objects that are vulnerable are al-ready, in a sense, bait traps. By using pheromones will we make them sex attractants as well? Pheromone traps are commonly used for long-term monitoring to determine the emergence patterns of the target insect, \\'hich means that there must be some adsorption of the pheromone on other materials. 10.3.10 Future a nd ethica l responsibility to hC"i tagc objects Pheromone traps are currently being developed for museum use. To test the effectiveness of the trap in attracting the target species is a difficult job. Insects have to be reared, marked and freed to see if the trap works and, as an added complication, the physiological state of the freed insects plays all important role in their response to pheromones. Because pheromones are natural products, it is automatically expected that their mode of action does not involve a toxic effect. This is not the case, and consequently synthetic pheromones are subject to the same registration and control as pesticides. Tn the use 70 Herilage Eaters of pheromones where food is processed, for eXillllple, a zero tolerance in the food is required (Burkholder and :\ la, 1985). The pheromones must be used according to the label because they are reg istered products and subject to regulation by eOS III-I-UK (Control of Substances Hazardous to Health) in the UK, by EPA (Environmental Protection Agency) in the USA and by PCPA(Pest Control Products Act) in Canada. In Canada pheromones cannot be used for mass eradication, only for monitoring, but in the USA they can be used for mass eradication. In addition, it is 1I0t known if there is any chemical inter-action w ith the chemicals of the object that would enhance deterioration. \Ye must always consider all aspects of our action towards heritage objects, which we have an ethical responsibility to preserve. 10.4 O VI POS I T I O~ THAI'S: IlAIT THAPS Your heritage objects are the best food traps: they have proved thenlselves successful over thousands of years. The odours from food traps have been designed to attract insects hunting for food and an oviposition site. Feeding behaviour involves food habit location, finding, recognition , acceptability and suitability. Oviposition involves a chain of behaviours, similar to feeding behaviour, resulting in the assessment of suitability and selection of the oviposition site. In museums and other buildings with natural and cultural heritage objects made of organic materials such as fur, skin, bones, etc., these objects are food traps in themselves. If they are infested, this proves the point. An approach to this problem is to use storage methods that prevent odours from the organic materials escaping the object area. Storage cabinets and object containers made of special materials, e.g. plast ics, glass, alu-minium paper, etc., which are impermeable to odours, can be used. For example, tins or boxes of spices can be placed inside glass bottles. Commercially available polyethylene or polypropylene food storage quality containers are ideal be-cause they prevent insects from entering and at the same time allow a view of the object without handling being required. 1 r by accident infested materials are placed in the containers the infestation will not spread to adjacent materials. HEFEH E.'ICES Blum. ,\1.S. 1985. Fundamentals oj illsect Physiology. John Wiley and Sons, Xew York. Chichestcr, Brisbanc, Toronto, Singapore. Burkhardt, O. 1977. On the yision of insects. Journal of Com para live Physiology. 120:33-50. Burkholder, \V.E. 1984. Cse of pheromones and food attractants for monitoring and trapping stored-product insects. J tlinsect l\lanage-ment for Food Storage and Processing, Ed. FJ. Baur. American Association of Cereal Chemists, St Paul, .\Iinnesota, pp69-86. Burkholder, \r.E. and '\1. '\ Ia. 1985. Phero mones for monitoring and control of storcd-product insects. Anl/ual Reviell' of EntomologY', 30:257-272. Child, H.E., 0.13. Pinninger, B .. Ashok and P. Smith. 1994. Jnsect trapping in museums and hisLOric houscs. Proceedings of the 15th IIC InternationaL Congress; Preventive Conservation, Ottawa, Sep-temher 1994, ppI29-131. Florian, \I. -L.E. 1987. \Iethodology used in insect pest survey in museum buildings - a case history. 8th TrienniallCOlll flleeting, Biodelerioration IForking Group, Sydney, Australia, September, ppI169- 1174. Gilberg, .\J. and H. Roach. 1991. The usc of a commercial pheromone trap for monitoring Lasiderma serricorne (F.) infestations in mu-seunl collections. Slildies in COl2sen'ation 36(1}243-247. Gilberg, \1. 1992. Pheromone traps for monitor ng insect pests in museums. Bulletin JlC-CG, 17(2):9- 14. Gilbert, D. 1984. Insect clectrocutor light traps.ln Iflsecl l\1anagemenl for Food Storage and Processing, Ed. FJ. BauL American Associa -tion of Cereal Chemists, St Paul , \Iinnesota, pp87- 108. Gullan PJ. and Cranston. 1995. The rnsects;/ln Outline of Entomology, Chapman and Iiall. London. Ilsi ao, II.S. 1972. /fllraction ofiWoths to Light and 10 Infrared Radiation San Francisco Press, California. Ja\·o\·ic!l, I. 1987. :\ew facilities for the prevention of damage by insect pests. \Iu::eumi Il/utargyv 17: I 99- 2 12. Jobin , L. and C. Coulombe. 1992. The Lliminoc~ Insect Trap. Informa-tion Leaflet l.Fe 2b, '\Iinistry of Supply and Services Canada, Ottawa, Canada. Keever, D.W. and L.D. Cline. 1983. Effcct of light trap height and light source on the capture of Catharus quadricoilis (Guerin- '\lene\' ille) (Coleoptera: Cucujidae) and CaLlosobruchus maculalUS (F.) (Coleoptera: Bruchidae) in a warehouse. Journal of Economic Entomology 76(5):1080-1082. Kronkright, D.P. 1991. Insect traps in conservation sun·e)'s. Sewsleller (lVestern Associationfor Art Conservation), 13(1):21-23. \Iallis. A. 1982. Handbook of Pest Control, 6th Ed. Franzak and Foster Company. Cleveland. Ohio. '\Iazokhin-Porshnyakov, G.,\. 1969. Insect f/ision. Plenum Press, New York. '\Ic\'eigh, L.J. , D.H. I Jail and P.S. Beeyor, Eds. 1993. insect Pheromones, IOBCj uiprs Hallet in, 16(10). Proceedings of the Working Group on "Use of Pheromolles and Other Semiochemicals in Integrated Control". JOBC, Houte de :\l arseille - B.P. 91, 84143, '\lontfavet, France . . \Ienzel, B. 1979. Spectral sensiti\·it.y and colour \'ision in invertebratcs. In Comparalive PhysioLogy and Evolution of Vision in Invertebrates. A: lrwerlebrate Photoreceptors, Ed. II. Autrum. Springer-Verlag, Berlin ,6A:503-580. ,\ Iote, \1. 1. and T.II. Goldsmith. 1970. Spectral sensitivities of color receptors in the compound eye of the Cockroach Periplaneta. Journal of E.xperimcntal Zoology, 173:137-146. "\ Iueller, O.K. 1982. Pheromones. Xew weapon against stored product insects. Pest Control, February: 22-24 . .,\Iuirhead-Thomson, R.C. 1991. Trap R esponses of Flying insects. Academic Press, London. ScobIe, \1. 1992. The Lepidoplera: Form, Function and Diversity. Ox-ford Cni"ersity Press, ~ew York. Scott, I I.G. n.d. Household and Stored-Food insects of Public Health rmportance and Their Control. U.S. Department of Public I lealth, Education and Welfare. Atlanta, Georgia. Zaitse\'a, G.A. 1991. Control of insects in museums: the use of light tra ps. Proceedings q./lile International Corifereflre ofBiodeterioration cf Cultural Property, Lurknoll", February 20-25, 1989, Eds. O.P. Agrawal and S. Ohawan, pp469-477. 71 11 The Insect Infestation: Finding, Bagging, Eradicating and Clean-up II.I T HE INS P ECT IO'i: BE PHEPAllE D 11 . 1.1 Pinpo in t the locati on orthe infes ta tio n Flying moths in a heritage collection or display areas means there is an infestation somewhere . .It has to be found. This requires an inspection and mon.itoring. \Ionitoringmeth-ods are described in chapter 10. If the collection area is large. monitoring, using sticky light traps of all sorts, may be needed to pinpoint the infestation. Once the area where the infestation is suspected to be is located, then an inspection of the individual heritage objects in that area follows. But before starting the inspection it is necessary to prepare the paperwork and parapher-nalia needed to deal with the infestation when it is fOWld. 11.1.2 \l a kc a n OO I" pla n First, make a floor plan or a drawing of the layout of the storage conta iners, cupboards, shelves, drawers, etc., and the location of the objects in or on them. The purpose of this is not only to mark the location of the infestation butalso to mark the objects inspected. If the inspection takes several days this record will tell you where to start again. The location of an infestation should also be accurately recorded in the IIPC programme (see chapter 13). 11.1.3 Keep a pe l'll1a ne nt r'ecor'd This record should be a permanent document and be included in a database, if possible. If objects are moved a record of their new location is necessary for object tracking. The record will be useful in the future for reference, to help with scheduling con tinual inspections and assessing the time required for inspecting the objects. 11.1.4 Ta ke ad nmtage o f' the inspection to clea n a nd upgr'ade s torage Inspection of individual objects may seem labour-intensive but it can contribute to many care requirements of objects. 1t is an opportunity to observe any conservation problems with objects. It is also an opportunity to upgrade the storage to facilitate quicker and easier inspections in the future, for example, placing white paper under the objects on shelves or in containers makes the darker faecal pellets easier to see. At the Royal British Columbia .\Juseurn a need to move the collection for asbestos abatement made us realize that storage is temporary and that objects in storage will eventually be moved. Thus the objects were stored individually in their own containers so that the objects would not have to be handled or packed and were always ready to be moved. T hese individual containers facilitate inspection of collections and pre\'ent spreading of insect infestations to ad jacent objects. I 1.1.5 Pre pare t he bags Prepare a variety of sizes of clear plastic bags on a tray or dolly (hand cart) for immediate access to facilitate rapid and easy bagging of any suspected infestation. Clear polyethylene bags are needed for the freezing treat-ment (sec procedures in this chapter). Clear or translucent, food quality, polyethylene containers with a tight lid seal can also be used. The object could be stored permanently in this type of container. Large objects call be wrapped in polyethylene plastic and sealed with freezer tape. The reason clear plastic is recom-mended is because it is necessary to observe the object to give it the physical support it needs during handling or when storing it, and to observe any insect activity. Seals for the bags do not have to be airtight, ties, ziploc (self sealing) or freezer tape can be used. T ags or labels should be attached to the bag with the date of bagging and any other identification needed. The tag can also be used to record the date and lime that the bag started and ended treatment. For small objects to be treated by anoxic treatment with an oxygen absorber (Gilberg, 1993; Gilberg and Grattan, 1994), gas-impermeable transparent bags (Burke, 1992) arc needed. 1n dealing with an infestation of extremely large objects the method recommended by Koestler ( 1995) using an anoxic gas can also be considered. The object can be isolated insilu by using a soft-walled enclosure system or bubble, custom-built around any size of inrested object or group of objects. Large objects can also be wrapped in polyethylene and moyed to a walk -in freezer. I f the objects are in boxes, bag the box. If the object is infested, the bagging will prepare it for the eradication treat-ment. :\0 matter what treatment will be used, when an infestation is found it must be confined to a bag or container. The infested object should not be removed from the bag until 72 Heritage Eaters after treatment to prevent contaminating other areas or ob-jects . .If the object is wet and infested. a rare event, a method of drying it must be devised using an insect-proof container, before the insect eradication treatment. 11.1.6 Ins pecting the o bjects The inspection of individual objects or specimens must be done slowly and thoroughly. Proceed from the top to the bottom of the cabinet, set of drawers or shelves. In the process of inspecting heritage objects it is usually necessary to handle or move the objects. The greatest amount of damage to heritage objects occurs during hand ling. Proper handling and moving techniques, according to conservation standards, must be understood . T his information is based on good common sense. Insects know when there is some minute change in their environment and instead of waiting around to find out what it is, they scatter. If the infested material is agitated, larvae tend to move away rapidly or if the object is picked up they drop and crawl rapidly away. Adults flyaway or hide. Insects, when disturbed, may give off an alarm scent which will alert other insects to your presence. Being prepared helps prevent the infestatIOn from spread-ing to other objects, maybe ones you have just inspected. Because of the insects' startle response, it is necessary to be prepared to confine the infested material immediately when observed. 11.1.i \\' ha t to look fo r' - f,'ass Frass is a give-away. First, without d isturbing the object, look for frass (faecal pellets); then insect rema ins, exuviae (moult skins), webbing, cocoons; and material fragments, on the shelf or paper under and around an object. The presence of any of these remains indicatesan infestation . The living insect stages are not commonly seen, they are always well hidden. I f fTass or any other evidence of insect activity is fOWld, get an appropriate bag, open it and bring it up to the object on the shelf and quickly slide the object into the bag and seal it with ziploc or tic. 1 f frass or other remains are not initially observed, examine the bottom and inside of the object. Often tweezers can be used for examination without distu rbing the insects. If any insect remains are present, again using the precautions already mentioned, bag the object. Do the bagging on the shelf without lifting the object away from the shelf. Place the bagged objects according to conser-vation standards - appropriate care in handling, packing, etc. - in a container which can be closed and easily moved to the place of treatment. Objects close to the infested object should also be bagged for examination and treated, if necessary. The area where the infested objects were located should be thoroughly cleaned (see chapter 13 for suggestions on methods). 11.2 EIlAD ICAT ION TIl EAT~ I ENTS The infested object should be treated immediately. The ba.gs are not intended to be insect· proof. :\Jost insects will not leave the object, the feeding site, but in infestations with adults, i.e. larder beetles, stored grain beetles, the adults may attempt to eSC<'l.pe. If wooden objects are infested with dry wood or powder-post termites, the termites may eat t heir way through the bag. Anoxic (see section 12.2) and heat treatments (see section 12.1 .3) for eradication are still in the research phase. For more information contact the authors of the research papers refer-enced for these treatments. The following reduced-temperature treatment (Box 11.1) is recommended for heritage objects made of organic materi -als which are dry (see sections 12.1.1 and 12.1.2 for details). 11.3 T H E CLEAN-UP - AFT ER ERADICAT ION TIl EAT~ I ENT [deally, the cleaning of all evidence of insect activity in heritage objects should be undertaken in a positive-pressure fume hood to prevent the spread of the frass. The reason for this is that some people are allergic to insect frass ahd also predatory insects are attracted to odours which may still remain in the frass or other debris from the infestation. It can be a long and arduous job to remove everything, especially cocoons embedded in textiles. If time prevents a complete removal of all evidence, a record and photographs showing what remains can be used as a reference po int to determine if a new infestation has occurred after storage. Uncleaned objects should be placed in a dense plastic box to prevent the odour from attracting other insects. 11.4 T HE EV IDENC E: W HO'S T HEilE, WHAT'S T HERE? In many cases it is possible to identify the culprit insect from the remains in the infestation. Unfortunately, this book is not an illustrated guide to identificat ion of the insects in the infestation. I t is an example of what may be there and an aid to identification. If infesta -tionsare found in your home or institute, make a manual of the different insect infestations found. Each site will have only a few insect pests, thus it will bean easy job. After the infesta tion has been treated. remove some of the insect evidence and place it on coloured index cards with clear adhes ive tape. Put the card in a ziploc bag and put this in the manual. H ave it ident ified and use it to identify future culprits. You will find: faeces (see Figure 11 .1) and some insect rema ins including wings and wing scales of adults (see Figure 11.2) and cocoons, exuviae and ha irs (setae) of larvae (Figures 11.3 and 7.10). Jf insect stages are fou nd the following chapters may help identify the insect species: eggs - chapter 6, larvae - chapter 7, pupae - chapter 8, and adults - chapters 9 and 10. [--leritageobjects made of wood may show evidence of insect activity by insect holes in the wood and falling faecal pellets. Table 11.1 has descr iptions of common wood beetle damage that will help identify the insect species. \Vith wood objects which show entrance and exit holes and falling Crass, it is almost impossible to tell if wood beetle larvae are active inside. But some methods have been successful. X-rays of bark on trees have been used in forest e n tomology studies to observe the difference between diseased and normal bark beetle larvaeafterattemptsat biological con trol. Heritage The insect infestation:finding, bagging, eradicating and clean-up Box 11.1 PROCEDURES FOR FREEZIN G IN SECT PESTS FOR ERADICATION IN DRY HERITAGE OBJECTS NUDE OF A DSORBANT ORGANIC MATERIAL 1. A normal household (domestic) chestjreezer which goes down to at least - 20'C should be used. Tempera-tures lower than - 200 to -30°C do not present a prob-lem . Because a constant temperature must be main-tained, do not use an upright freezer or one with a frost free cycle. The freezer must be maintained 50that there is no frost build-up on the inside of the lid or sides. 2. The method of removing an infested object from stor-age requires that the object be placed in a clean, clear, polyethylene bag. Precautions should be taken when bagging infested materials, because as soon as the object is moved the insects will respond and try to escape. Prepare the bag in advance and seal it immedi-ately when the object is placed in it. Sealing does not have to be airtight; ziploc, ties or tape are adequate. ,~rhen the object. is first bagged remove as much air as possible, the amount of remaining air will depend on t.he stability of the object and its tolerance to the pressure of the film against it. Bagging is also necessary to confine the infestation when using a specially con-structed, controlled temperature and humidity freez -ing chamber. The object should remain in its bag during the freezing treatment. 3. If the object is large, with large air spaces around it, pre-treated silica gel or additional adsorbent material , such as clean cotton towels or sheet ing, etc. , can be included with the object in the bag. 4. Bagged infested objects should be kept at room tem -perature (above 18°C) and placed immediately in the chest freezer. The freezer temperature should already be at least - :W°c. In an emergency they may be placed in a refrigerator at 5°C until freezer space is available, but should not be temporarily stored in a cold base-ment or cold storage with temperatures above 5°C. This temperature, 5°C, is the chill-coma tempera-ture, the point at which the insects become inactive, do not feed , thus do no further damage. It is imperative that these bagged objects held at 5°C are brought back to room temperature (approximately 2(f>C) before placing them into the chestJreezer which is already at - 2(f>C or lower. 5. There should be adequate air circulation around the object to allow it to cool to at least 5°C in 4 hours. Dense objects, i.e. wood , boxes of newsprint or books, or a bag of flour, may need more time to reach a core tempera-ture of -~woC. T he extra time it takes for the materials to reach a core temperature of -20°C should be added to the treatment t ime. 6. Thermocouples can be used to record the time/ tem -perature parameters of t he freezing procedure, i.e. the rate of cooling and thawing, and the time at the mini-mum temperature. 7. T he minimum temperature for insect eradication was established at - 20°C, but a lower temperature of - 30°C has been recently recommended . Because the reaction is time/ temperature dependent the following are now recommended: 72 hours at - 2(f>C to - ](f>e. There is no need to adapt the freezer for the - 30°C temperature, one can simply extend the treatment time. If there are any concerns about the effectiveness of these treatments or possible cold-hardiness of the insects one can , as a precaution, extend the time or immediately repeat the freeze/ thaw cycle, that is bring the materials to room temperature and then place them back in the freezer to repeat the cycle. Repeating the cycles has the disadvan -tageofincreasing the handling of the objects. Objects do not have to be removed after exactly 72 hours , they can be left in the chest freezer for a longer time, hours, days , or weeks without damage. 8. Remove the bagged objects from the freezer and place them in a secure area where there is good ventilation. Caution must be taken in handling and moving the cold objects. In some cases where a material has become stiff (plastics, acrylic glues, oil paints) extra precautions should be taken in handling these objects. Do not re-move the bag until the object. has reached room tem-perature and there is no condensed water on the outside of the bag. If possible, leave objects in the polyethylene bag for storage. A slow rate of thawing is desirable. The passive increase in temperature of objects that occurs when they are taken from the chest freezer (-20°C to - 30°C) and placed at room temperatures, around 20°,C is slow enough. In an abnormal situation under high room temperatures, move materials directly from the fTeezerinto a refrigerator or cold storage and leave them there until at ambient temperature. Another alternative is to turn off the chest freezer and leave the objects in the freezer until it has reached room temperature, but precautions must be taken to assure that there is no frost build-up inside which would melt and be a potential hazard to the objects. 9. All insect remains (frass, cocoons, exuviae (moults) , larvae, etc.) must be removed from the treated object before re-storage. This establishes a reference point at which there are no insect remains, a zero point. This is the only way to know, for certain, that insect remains are from a new infestation and not from a previous infestation. 10. Because the freezing process is an interventive conser-vation treatment, details of the treatment should be recorded in the treatment documentation for the ob-jects. The record should include: insect identification, stages and activity of the insect; packaging materials and method; time required to bring materials to O°C and to minimum temperature; t ime materials were held at minimum temperature; time required to bring materi-als to room temperature; anyphysicaJ changes observed, and the success of the treatment. It is not necessary to do this with every freezer load. The above information can be established for specific materials and object type and a standard treatment form used. 7J lIeritage Eaters b d The insect infestation:fin(lt:ng, ba{{{!il1{!. eradicating and cleal/ up f g Iz r-----Figure 11.1. Scanning electron micrographs of faecal pellets cif beetle and moth lan·ae and termite adults .. a, T ineola bisse ll ie lla (I lumnzel), ll"ebbing clothes moth (#9601- 960J): b. T inea pellionella (L.), case-making clothes moth (#9604-9605),- c, Reticulitermes hesperus. Banks u·estern subterranean termite (#9606-9607) : d. llylotrupes bajulus (L.), old house borer (#9608- 9609),- e. Anob ium gibbicollis (LeConte), anobiid powder-post beetle (#9610-9611),-J, Zootennopsis a ngusticollis (J1agen), damp fl'ood termite (#9615-9616); {!.lIcterobostrychus aequalis (lVaterhouse), orientalll"ood borer (#9617-9618); Ii. Anthrenus verbasci (L.), I"(lried cmpet beetle (#97..J.}- 97-14) : i. Dcrmcstes maculatus (De Geer), the hide beetle (#97-1-5- 97-1-6)' (l /icrographs taken ill Scanning Electron J /icroscopy Laboratory, Pacific Forest Centre, Canada Forest Centre by L esley Halllling, ),licroteclmique Biologist.) 75 76 Heritage Ealers b d J g Figure J 1.2. IVing scales of some common adult heritage-eating insect pests. a, Tineola bisselliella (rlummel), webbing clothes moth; b, Endrosis sarcitrella (L.), u;liile shouldered house moth: c, Tinea pellionella (L.), case-making clothes moth; d, Anthrenus verbasci (L.), varied catpet beetle; e, Anthrenus museorum (L .). museum beetle;], A nthrenus sarnicus 1\lroc::.koll'sk~· g, Anthrenus fuse us Olivier; h, Anthrenus scrophulariae (L.), common catpet beetle. (a-c, M-L. Florian.; d-h., from Peacock, 1993, ("'jtil permission.) The insect irifeslalion:findillg, bagging, eradicating and clean-up 77 b Figure 11.3. a, Ligh.t microscope photograph and, b, scanning electron micrograph of arrou'-shaped hastisetae and thick spinulale setae of the lan)ae of Anthrcnus verbasci (L.) varied carpel beetle. (Light microscopy, JJ-L. Florian.; SE.W, Scanning Electron _Wicroscopy Labor-atory. PaciJic Forest Centre, Calwda Forest Centre by Lesley tvJanning, ~l;Jicroteclmi.que Biologist) objects have been X-rayed with some success, but it is difficult to know if the larvae observed are alive or dead. Time-lapse X-rays have been used to demonstrate extension of the tunnels. The sound of the rasping mandibles of the feeding larvae has been detected by stethoscopes and electronic sound de-vices. Koestler (1993) reported that an infrared COl analyser, FTIR (Fourier transform infrared spectroscope), has been used to detect insect activity in stored grain by the CO) they produce above the background of 0.03°/0 (300ppm). Ko-estler (1993) has developed a modified C01-FTIR and has tested it with a wooden picture frame infested with termites. He was able to show that before treatment there was a COl level above the background, but after treatment with an anoxic gas the CO, level dropped. 11.6 FIXDI :\"G TilE P C PA After the insect has been identified check (see chapter 7) to determine if the larvae wander to build the pupation chamber away from the feeding site. Jf this is the case, a thorough inspection in the storage area where the infestation was located is essential. The pupae may be in wall cracks or under flooring and not easily seen. Scenal' io: findin g the pupa In dealing with a webbing clothes moth infestation of natural history specimens of mountain sheep skulls with their horns, the author found that the larvae on the specimens and adults were caught on light traps.:\o thought was given to the pupae, expecting they would be in the interstices of the horn. \Yithin two weeks after what was thoughtto bea thorough eradication of the infestation, new adults were c<lught on the light traps. On close examination of the walls and floor area around the skulls it was found that pupae were located in cracks of the cement. where the wall and floor meet. They were physically removed and there has not been a recurrence of the 1110th activity. G E.'IE lv IL A:\"D CI LIPT ER REFERENCES Bletchly. J.n 1967. Insect alld Harine Borer Damage 10 Timber alld IVoodu'ork .\Iinistry of Technology: Forest Products Research. I ler \Iajesty's Stationery Office, I,ondon Burke, J. 1992. \apor barrier films. SelL'sleller, IVestemAssocialionJor Art Conseroalioll, 14(2):13- 17. Eberling, \Y. 1975. Crban Entomology. Uni\-ersity of California, Los .\ ng:eles, p.695. Florian, .\l-L.E. 1986. The freezing process: effects on insects and artifact materials. Leather Consen'ation \TeU'~leUer 3{ I): 1- 13 and 17. Florian, .\I-L.E. 1987 . .\Iethodology used in insect pest survey in museum buildings, a case history. 8th Triennial ICOH Heeling, Biodeterioration Irorking Group, Sydney Australia, September, ppI169- 1174. Florian , .\l -L.E. 1992. Saga of the saggy bag. Leather Cowef'!:ation \ ·ell's.8:1 - 11. Gilberg, \\. 1993. Inert atmosphere disinfestation of museum objects using Ageless oxygen absorber. 2nd intemational Coriferenre on Biodeterioratiofl ojCultural Property, }Tokohama, Japan, pp397-406. Gilberg, .\l.and D.\\'. Grattan. 1994 . . \geless oxygen absorbN: chemical and physical properties. Studies ill COlISen'atioll, 39(3): 210-214. Koestler, H.J. 1993. Insect eradication using controlled atmospheres and PT1R measurements for insect acti\-ity. leOH CommitteeJor Conserration 10th Triennial Jfeetings, lI 'ashingLOn, D.c.. pp882-885. Koestler. H.J. 1995. Hethods oj control/inft biodeterioation infine art: an Kulturguterhaltung: Problcmdefinition und I,osungsmoglichkeiten. Beitrage \\ orkshop. Oktober in \Yein, \~eranstalted yom ostcrreichischen El-nOCARF. Sekretariat. BIT ElJROC.\RE Sekretariat, \\iedner Ilaupstrasse 76, .\ - 1040 \\'ein pp.7-14. \lallis, A. 1982. Handbook ojPest Control, 6th E.d., Franzak and Foster Company, Cleveland. Ohio, p1099 . .\Iourier, II. and O. \Yinding. 1977. ColLins Guide To II 'ild Life in /-louse and flome. Collins, St. James Place, London. Olkowski, \\' " S. Daar and II. Olkowski. 1991. Common-Sense Pest ControL. The Taunton Press, '\e\\'town. c r, p.71">. Osmun, J.\- 1984. Insect pest management control. [n Insect Hanage-mentJor Food Storage and Processill{!, Ed. FJ. Haul' .. \.A. of Cereal Chemists. St. Paul, .\linn. pp 1 5- 24. Peacock. E..H. 1993. Adults and Lan-·ae of flide, Larder and Carpet Beetles and Their Relati"es (Coleoptera: Dermestidae) and oj Derodontid Beetles (Coleople"a: Derodontidae) . Ilandbooks for the Identification of British Insects \'01.5, Part 3. Hoyal E.ntomological Soeiet\" of London. 78 Heritage Eaters Table J 1.1 Summary cf'diagnostic characters qf damage caused by lhe commoner u;ood-boring insects alld marine borers (from Blelch/y, 1967) Type of timber I I I attacked (sapwood & heartwood Type of -exceptions given Flight holes Tunnels Bore-dust CFrass) insect or Remarks under remarks) marine borer S = Softwood; H = Hardwood Chiefly imported Absent or Partly concentric with - Carpenter ants Resembles te