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The external morphology of AOPLUS CESTUS (Cresson), (Hymenoptera: Ichneumonidae), a parasite of the oak… Miller, Charles Douglas Fairbanks 1951

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L- £~ 5  THE: EXTERNAL MORPHOLOGY OF AOPLUS CESTUS (HYMENOPTER&:  (CRESSON),  ICHNEUMONIDAE),  A PARASITE; OF THE OAK LOOPER AND HEMLOCK LOOPER I N B R I T I S H  COLUMBIA  by CHARLES DOUGLAS FAIRBANKS M I L L E R Technical Officer 2, Biological Control Investigations Vancouver, B. C.  Laboratory,  A T H E S I S SUBMITTED I N P A R T I A L F U L F I L M E N T OF THE REQUIREMENTS  6  MASTER OF  i n the  FOR. THE; DEGREE OF  V  UMMJ&  Department of  Zoology  We a c c e p t t h i s t h e s i s a s  conforming to  standard required from candidates f o r degree o f  MASTER OF  Members o f  the  THE: U N I V E R S I T Y OF B R I T I S H April,  1951  Department  COLUMBIA  of  the the  3  7  Abstract  The e x t e r n a l m o r p h o l o g y o f A o p l u s c e s t u s  (Cresson),  p a r a s i t e o f t h e oak l o o p e r and hemlock l o o p e r i n B r i t i s h described.  An attempt  highly-modified insect  i s made t o h o m o l o g i z e t h e  an Ichneumonid Columbia,is  structures  w i t h t h o s e known i n more g e n e r a l i z e d  i n t h e h o p e o f c l a r i f y i n g some q u e s t i o n s have been n e g l e c t e d b y e n t o m o l o g i s t s . f r o m a u t h o r s whose n o m e n c l a t u r e i s  - i i i -  this  insects,  o f Ichneumonid morphology which  T h e t e r m i n o l o g y u s e d was  generally accepted  morphologists•  of  by  selected  present-day  Index  Abstract  i i i  Introduction  1  S t u d y and i t s purpose Economic p o s i t i o n Systematic p o s i t i o n  3 3 3  Acknowledgments  4  M a t e r i a l s and Techniques  5  G e n e r a l Anatomy  6  The Head  8  Exoskeleton Head s c l e r i t e s  8 8  Endoskeleton The t e n t o r i u m  11 11  The H e a d A p p e n d a g e s The t r o p h i  12 12  The C e r v i x  15  The T h o r a x a n d E n d o s k e l e t o n  16  The The The The  prothorax pterothorax mesothorax metathorax  16 18 20 22  The L e g s  24  The l e g a r t i c u l a t i o n s The W i n g s  25 26  The f o r e - w i n g The h i n d - w i n g The a x i l l a r y s c l e r i t e s The Abdomen  28 29 30; 32  The p r e g e n i t a l s e g m e n t s The g e n i t a l segments The p o s t g e n i t a l segments - i -  32: 34 34  The G e n i t a l i a  34  The f e m a l e g e n i t a l i a . The m a l e g e n i t a l i a  35 36  Summary  39  Literature Gited  40  - i i -  Introduction  Modern t a x o n o m i s t s factory tics  g e n e r a l l y agree that  for determination of  species.  has  c r i t e r i o n f o r d i s t i n g u i s h i n g groups of p l a n t s c a t e g o r i e s one f r o m t h e o t h e r .  s i n g l e means f o r i d e n t i f i c a t i o n o f teria it  e v o l v i n g from g e n e t i c a l ,  m u s t be r e m e m b e r e d  the  study of  (1949).  the classic ment o f the  He r e l a t e s :  role that  empirical fact  characteristics,  the  this  not replacements  but  is  writes,  that  animals  cribut  supplements  for  are mine.) its  morphology has  and p l a n t s  w e l l as  played i n the t i m e s man h a s  c a n be s o r t e d  into higher groups.  system devised  From t h i s  i m p o r t a n c e was a t  and s u b s e q u e n t l y true,  by Linnaeus  is  described appreciates  developrecognized  by_ m o r p h o l o g i c a l can  the  concise  i t c a n be s e e n t h a t m o r p h o l o g y i s first  (The  important;  o v e r s t r e s s e d and c o n s e q u e n t l y of plants species.  i n c l i n e d t o c o n c u r w i t h Brown  g e n e r a l l y and i s  led  and Though  (1949) w h e n  "The p l a c e o f morphology i n s y s t e m a t i c s , abused and being re-evaluated  be  One o f t h e m o s t  s p e c i e s and o f t h e h i g h e r g r o u p s " .  t o an a r b i t r a r y d e f i n i t i o n of  the author i s  is  best  w i t h g r e a t e r o r l e s s d i f f i c u l t y , i n t o groups t h a t  features of the  i n the past,  a  studies,  studied biology  systematists to a purely arbitrary c l a s s i f i c a t i o n  animals,  highest  power as  and e c o l o g i c a l  Since the e a r l i e s t  morphological d e f i n i t i o n of the  in fact,  of the  d i m i n i s h i n g due t o t h e  " E v e r y o n e who h a s  comparative  c a l l e d k i n d s o r s p e c i e s , as  italics  and animals  of the r o l e of morphology i n the past i s  systematic biology.  important  physiological,  these are  been the o n l y f u n c t i o n a l  Admittedly, i t s  species i s  systema-  morphology.  The i m p o r t a n c e by Brown  that  satis-  The r o l e o f m o r p h o l o g y i n  i s u n s u r p a s s e d , and u n t i l r e c e n t l y i t  and lowest  no one c r i t e r i o n i s  he  misunderstood  secure because of  the  2 empirical fact that the majority of animals can be sorted into groups that we c a l l species.  And without an appreciation of morphological relation-  ships, one cannot easily and quickly deduce knowledge of a strange species to the benefit of a practical problem". The import of the latter statement may be realized when we examine the purpose behind the morphological study of the hymenopterous thorax by Snodgrass (19U).  He states:  "The gypsy moth and brown t a i l moth have  been for a number of years greatly infringing on human interests and pleasure in certain parts of New England. A most promising means of combatting them i s the importation and rearing of destructive hymenopteran parasites. Students of these parasites discover that the thorax presents valuable characters for the determination and classification of species, but they are handicapped by the lack of reliable studies on the structure of the thorax among the parasitic Hymenoptera i n general".  Because of this lack  of knowledge of the hymenopteran thorax, Snodgrass undertook the study. He found later that i t not only entailed a study of the thoraces of the parasites, but also of the lower Hymenoptera i n order to obtain the homologies of the more specialized group to the generalized and more primitive insects.  He explains that "experience shows that no special branch of  entomology can be developed properly unless based on a knowledge of the fundamental structure of insects i n general". The importance of morphology as a part of present day systematics i s stressed by the comments of Ferris (1928). He relates that systematic entomology i s simply the study of comparative morphology with the formulation of conclusions as to morphological relationships, and that, though morphology has limited aims (such as attempts to correlate structure and  3 function), beyond this i t is nothing but the study of the basic data of systematics.  Furthermore, he points out that any systematic entomology  which ignores this fact is cutting itself off from the right to be regarded as a science. Feelings such as these, expressed by men who are respected authorities in their fields of endeavour, justify and keep secure the study of morphology as a science in its own right, and should convince us that, although diminishing in power as a single criterion for definition of species, i t s t i l l plays and always will play a leading role in biology. Study and its purpose. This paper is a morphological study of a parasitic hymenopterous fly belonging to a sub-family much neglected by insect taxonomists. The subject was suggested by the Canadian hymenopteran authority, G. S. Walley, whose opinion is that such a study will lay down a basis for further studies, taxonomical or morphological, of this group of insects. Economic position. Economically speaking, Aoplus cestus (Cresson) may be considered a beneficial insect.  It provides a potential weapon to combat and control  epidemics of the oak looper, Lambdina somniaria (Hulst), and the hemlock looper, Lambdina fiseellaria lugubrosa (Hulst), serious insect pests of two of our important forest trees. Systematic position. Aoplus cestus (Cresson) was originally described by E. T. Cresson (1878) from material collected on Vancouver Island.  At this time i t was placed  in the genus Ichneumon. A recent revision of the classification of the Nearctic Ichneumonidae by Townes (1944), however, has placed this species  in the genus Aoplus, giving i t a new combination—Aoplus cestus (Cresson). The genus Aoplus was originated, by Tischbein i n 1874, but was not used for Neaatic species u n t i l 1944 at which time Ichneumon cestus Cresson and thirteen other species were referred to i t .  The majority of these  species (including cestus) had previously been placed i n the genus Ichneumon (sometimes referred to as Amblyteles). The genus Ichneumon has had a complicated nomenclatorial history, but i n general has been used by early authors such as Cresson, Provancher, Ashmead and Viereck for numerous species currently assigned to many of the restricted groups now placed i n various tribes of the Phaeogeninae. In Townes' (1944) classification, Aoplus cestus (Cresson) i s placed as follows::— Family—Ichneumonidae Sub-family—Phaeogeninae Tribe--Amblytelini Genus—Aoplus Species—cestus In this classification, the family Ichneumonidae i s divided into twelve sub-families,among which Phaeogeninae stands fourth.  This sub-family i s  composed of nine tribes, Amblytelini standing seventh. The tribe Amblytel i n i i s subdivided into sixteen genera i n which Aoplus i s placed fourth, between Cratichneumon and Patroclus.  Fourteen spcies of Aoplus are recog-  nized i n America north of Mexico. Acknowledgments The author wishes to express grateful thanks to Professor W. A. Clemens, Head of the Department of Zoology, University of British Columbia, for his permission to present this paper as partial fulfillment of the requirements for Master of Science i n Agriculture degree, and to Professor G. J. Spencer,  I  5.  Department  of Zoology,  of the work.  for his  d i r e c t i o n and c r i t i c i s m s d u r i n g t h e  The a u t h o r w o u l d a l s o l i k e t o  progress  express h i s appreciation  to  M r . A . B . B a i r d , Head, B i o l o g i c a l C o n t r o l I n v e s t i g a t i o n s  Unit,  Mr.  Investigations  J.  H . McLeod, O f f i c e r - i n - C h a r g e ,  Laboratory,  Biological Control  U n i v e r s i t y of B r i t i s h Columbia, f o r a l l o w i n g him to  t h i s work i n c o n j u n c t i o n w i t h o t h e r work c a r r i e d on a t laboratory,  and f o r t h e use  of t h i s  M r . G. S. W a l l e y , Systematic U n i t ,  laboratory's Ottawa, f o r  f o r g i v i n g him information concerning the insect,  Ottawa,  and f o r r e f e r e n c e s t o  the  and  prepare  Vancouver  facilities;  and  suggesting the  to  problem,  systematic p o s i t i o n of  the  literature.  M a t e r i a l s and  Techniques  The m a t e r i a l was c o l l e c t e d i n V i c t o r i a ,  B. C . , i n the areas  infested  d. b y t h e oak l o o p e r .  The s p e c i m e n s s t u d i e d w e r e c l e a r e d  s o l u t i o n of potassium  hydroxide.  a l c o h o l and g l y c e r i n .  Because o f the i n s e c t ' s  h y d r o x i d e was  cent  A l l d i s s e c t i o n s w e r e made i n 70 p e r  unnecessary t o bleach o r s t a i n any of the w i t h potassium  w i t h a 10 p e r  sufficient  light colour,  skeletal  parts.  to permit the.study  it  The  cent  was clearing  of the  complete  skeleton with l i t t l e d i f f i c u l t y . The s k e l e t o n was piece.  examined t h r o u g h a L e i t z b i n o c u l a r w i t h a squared  The l a t t e r made i t p o s s i b l e t o  draw t h e v a r i o u s  parts to  s q u a r e d paper f r o m w h i c h t h e i l l u s t r a t i o n s were t r a n s f e r r e d board f o r  reproduction.  to  scale  Bristol  eyeon  6. General Anatomy Since A. cestus i s an Ichneumonid, i t i s typical of the suborder Glistogastra as defined by Comstock (1936).  The tergum of the f i r s t  abdominal segment i s attached to and forms the propodeum (Fig. 16 IT) of the thorax. The second abdominal segment (Fig. 57, 58 11T) i s strongly constricted.  It forms a slender petiole, or waist, between the alitrunk,  or wing-bearing region of the body, and the larger portion of the abdomen. This species averages i n over-all length 10.5 mm. for the female, and 12 mm. for the male. The head and body are approximately 2 mm. wide.  The  head i s as deep as i t i s wide. The thorax i s approximately 4 mm. long and 2.5 mm. deep. The abdomen of the male i s from 1.5 mm, to 2 mm. longer than that of the. female. The integument i s relatively thick, tough, and elastic, and i s transparent when the body i s cleared with potassium hydroxide. The surface i s punctate and i s covered with fine hair which i s sometimes d i f f i c u l t to see except i n some lights. are  sculptured.  The metanotum (Fig. 28, 29, 3 0 N3) and propodeum  The latter i s slightly excavated behind, and i t s dorsal  posterior angles are bluntly spiniform (Fig, 29 IT). The sculpturing of the propodeum makes i t d i f f i c u l t and sometimes impossible to distinguish the lateral, central, and other propodeal areas used by inseet Systematists in their descriptions of other hymenopteran groups. The body varies from a dark to pale ferruginous colour, but the f o l lowing parts are black:—the distal parts of the mandibles, most of the ocular sclerites, the occiput, the prosternum, the anterior and lateral surfaces of the mesonotum, most of the prepectus, the posterior margin of the mesosterntun,  foveas.  ^he scutellar favac, the paraptera of the metapleura,  7 t h e base o f t h e propodeum, most o f t h e metasternum, quarter to one-half  of the true  is  u s e d i n Keys t o d i s t i n g u i s h t h i s  a characteristic  related  species.  author,  however,  ter  is  (it  species).  specimens  specimens,  suspected that t h i s i s  near i t s  (1937).  the h a m u l i ( F i g . Except  defined  by  y e l l o w i s h - h y a l i n e , and forms  to which they are  same c o l o u r a s  the body.  than the middle l e g s , which are a l i t t l e The a n t e n n a e o f b o t h s e x e s a r e  a  The h i n d - w i n g s a r e much attached  during f l i g h t  segments.  larger  than the front  approximately the  The t w e l f t h t o  which i s  by  fuscous,  The h i n d l e g s a r e much  seventeenth  t h a n t h e o t h e r s e g m e n t s ; i n some c a s e s t h e c o n t r a s t  larger  legs.  same s i z e  and bear  segments a r e  the  lighter  i s more d i s t i n c t  than  other* Except f o r a  s l i g h t v a r i a t i o n i n c o l o u r and s i z e ,  g e n i t a l i a , t h e male and female reason, all  oblique,  52B).  the legs are the  in  as  charac-  the  b e a r s two t r a n s v e r s e ,  f o r the d i s t a l portion of the hind t i b i a e ,  same n u m b e r o f  closely  lacked this  a n t e r i o r margin, the gastro-coeli  fore-wings  black  due t o c o l o u r v a r i a t i o n w i t h i n  The w i n g membrane i s  one-  c o l l e c t e d and examined by t h e  c o n t r a s t i n g background f o r the brownish v e i n s . smaller than the  This  species from  probably teneral,  The t r u e t h i r d a b d o m i n a l t e r g i t e  quadrate p i t s Torre-Bueno  f o u r t h abdominal t e r g i t e .  In the series of some m a l e  and t h e b a s a l  and t h e f a c t  that  of  cestus are  almost  and d i f f e r e n c e s identical.  o n l y a l i m i t e d s u p p l y o f f e m a l e s was  t h e i l l u s t r a t i o n s w e r e made f r o m t h e m a l e e x c e p t  For  in this  available,  where o t h e r w i s e  stated.  8. The H e a d Exoskeleton From t h e a n t e r i o r a s p e c t in  shape.  The d o r s u m i s  ( F i g . 3), t h e head o f  slightly flattened.  w h i c h a r e made u p o f t h e compound e y e s gnathal region. by W a l k e r The h e a d  The h e a d i s  (1932),  The s i d e s ,  (E), are  hypognathous,  cestus i s  circular  three-quarters  s t r o n g l y curved at  a condition considered  and p r i m i t i v e by Snodgrass  the specialized  (1935).  sclerites.  M o d i f i c a t i o n o f t h e h e a d c a p s u l e o f Jju c e s t u s b y c o m p l e t e f u s i o n some s c l e r i t e s , impossible  and changes i n p o s i t i o n and shape o f o t h e r s ,  to l i m i t  i n the generalized c r a n i a l regions The f r o n s  exactly the various insect  are  head.  d e f i n e d as  areas designated  is  t h e narrow a r e a between t h e (MO)  The c l y p e u s  or  (AT), landmarks  (ES)  for this  the  sclerite  i n which are  i t .  located the anterior  to  epistomal  tentorial  suture.  to the v e n t r a l margin of the clypeus.  Its  t h e p r e o r a l c a v i t y , w h i c h ends a t  flexibly  inner surface i s  the i n n e r surface of the c l y p e a l region o f the head,  The p a r i e t a l s  usually  immediately ventrad  The l a b r u m ( F i g . 3 6 LM) i s t h e f l a p - l i k e s c l e r i t e  of  the  accomo-  The f r o n s  separated from the l a t t e r by the p o o r l y - d e f i n e d  fronto-clypeal suture  pits  (BS).  and t h e a r e a i m m e d i a t e l y around  ( F i g . 2, 3, 6 C L P ) i s  It is  (1935)  (CLP).  between and above t h e a n t e n n a l s o c k e t s i n o r d e r t o  i n c l u d e s the median o c e l l u s  it  antennae  to the clypeus  d a t e movement o f t h e l a r g e b a s a l a n t e n n a l s e g m e n t s  the f r o n s .  purposes,  of  follows:—-  ( F i g . 1, 3 F R ) i s  excavated  h a s made  by Snodgrass  However, f o r d e s c r i p t i v e  s t r e t c h i n g v e n t r a l l y from the median o c e l l u s It  of  the o r a l  ( F i g . 2, 3, 4, 5 P R T L ) a r e  attached  continuous  or epipharyngeal  with wall  aperture. the l a t e r a l areas of the  head.  Each parietal bears a large compound eye (E), a lateral ocellus (LO), and an antenna (BS).  They are rather large i n JL cestus» and make up a large  part of the head. The vertex (Fig. 2, 4, 5 VX) i s made up of the dorsal surfaces of the parietals.  It i s the area directly posterior to the lateral o c e l l i and  between the compound eyes.  Since the head i s wide i n  cestus, the vertex  i s correspondingly large. The genae (Fig. 2, 3, 4, 5, 6 GE) are the ventral areas of the parietals.  They are considerably reduced i n Aj_ cestus due to the large compound  eyes. The occipital arch (Fig. 4 OC) i s a large, concave, horseshoe-shaped sclerite forming the posterior wall of the cranium.  Its dorsal and  lateral positions surround the small occipital foramen (FOR), the posterior ary  aperture through which pass the alimenta^ canal, nerve cord, and salivary glands.  It i s separated from the parietals by the ridge-like occipital  suture (OGS), which meets the subgenal suture a short distance from the mandible (Fig. 4, 5).  The ventral areas of this sclerite are termed the  postgenae i n generalized insects, and are sometimes, according to Snodgrass (1935), divided from the upper part, or occiput, by a suture. In this species, the two are solidly fused, and one can only refer to the postgenal area as the ventral portion of the occipital arch.  The area of  the occipital arch surrounding the occipital foramen i s bent posteriorly, and forms three occipital condyles (Fig. 4 OCC), one dorsal and two lateral, for articulation with the prothoracic segment. This area i s referred to by Snodgrass (1935) as the postocciput, and i s usually separated from the occiput by a postoccipital suture, which i s identified by the presence of  10. the posterior tentorial pits.  The posterior tentorial pits (PT) are  present i n Aj_ cestus, but no trace of a suture separating the occiput from the postoccipital area was located. Snodgrass (1935) has referred to this suture i n generalized insects as the only suture of the definite insect head that persists after fusion of the various head segments of the insect ancestor.  Apparently, most of this suture i s obliterated i n A.  cestus, and a l l that remain are the tentorial p i t s . The subgenae (Fig. 4, 5 SGE) are long, narrow sclerites on the ventral edges of the occipital arch from which they are divided by subgenal sutures. They extend to the neck region where their inner margins are extended mesally, and are united i n a broad hypostomal bridge (HB), which separates the labio-maxillary complex from the occipital foramen and cervical region. Bucher (1948) refers to this region in Monodontomerous dentipis Boh., an entomophagous chalcid, as the gular region, a term generally associated with a prognathous condition of the head.  It should be noted that i n  Snodgrass's explanation of the gula, the posterior tentoral pits are always anterior to the gular region, and i n his explanation of the hypostomal bridge these pits are always posterior to this region.  Therefore,  the area designated the gula by Bucher i n Mj_ dentipis i s more likely a hypostomal bridge.  This bridge, according to Snodgrass (1935), begins i n  the adult Tenthredinidae as elongations of the hypostomal region of the subgenae. Therefore, i f we are to accept the fact that the Tenthredinidae are the ancestors of the higher Hymenoptera, we must refer to this region as the hypostomal bridge and not as a gula.  'The region immediately  posterior to the hypostomal bridge and between the posterior tentorial pits i s strengthened on each side by sclerotized interal ridges (ITR),  11. externally revealed by a darkening of the chiton. Endoskeleton. In  cestus, the epistomal, postoccipital, and subgenal sutures of  the head a l l produce small internal ridges which make up part of the head endoskeleton, provide for muscle attachment, and undoubtedly add to the support of the exoskeleton. The ocular sclerite (Fig. 2 OSC), which frequently appears i n generalized insects as part of the exoskeleton surrounding the compound eyes and marked off from the rest of the cranium by an ocular suture, forms i n A. cestus an internal funnel-like flange, which separates the ommatidia of the compound eye from the rest of the organs of the head. Though this sclerite i s part of the exoskeleton i n generalized insects, i t definitely forms part of the endoskeleton of  cestus. Except for a narrow margin  around i t s basal part, this sclerite i s almost completely black i n colour. It i s marked off from the rest of the cranium by an ocular suture (OS). The tentorium (Fig. 2, 4. 5. 6). The exoskeleton of insect heads i s generally supported by an endo— skeletal framework, the evolution of which i s s t i l l doubtful. This framework i s referred to as the tentorium.  In JU cestus, i t consists of a pair  of anterior arms (Fig. 6 ATA), a pair of dorsal arms (DT), and a tentorial bridge (TB). The anterior tentorial arms are developed from invaginations of the epistomal ridge formed by the epistomal suture. Their formation causes a a pit-like impression on each side of the clypeus i n the epistomal suture. The arms are narrow and rod-like.  They are expanded mesally and laterally,  producing broad transverse lamellae (TL), which probably give support to  PLATE I  Fig. 1.  Dorsal aspect of head (25x).  Fig. 2.  Lateral aspect of head—compound eye removed to show ocular sclerite (25x).  Fig. 3.  Anterior aspect of head (25x).  Fig. 4.  Posterior aspect of head (2$x).  Fig. 5.  Posterior aspect of head—occiput and labiomaxillary complex removed to show endoskeleton (25x).  Fig. 6.  Anterior aspect of head—frons, vertex, and labio-maxillary complex removed to show endoskeleton (25x).  AN—antennifer;  ASG—antennal socket; AT—anterior tentorial pit; ATA—  anterior tentorial arm; BS—basal antennal segment; CD—cardo; CLP--clypeus; DT--dorsal tentorial arm; E—compound eye; ES—epistomal suture; FR—frons; FOR—occipital foramen; GA—-galea; GEr—genae; HB—hypostomal bridge; ITRt— internal ridge; LB—labium; LBPLP^-labial palp; LIG—ligula; LM—labrumj LO—lateral ocellus; MD—mandible; MO—median ocellus; MXPLP--maxillary palp; OG)--occiput; OCC—occipital condyle; OCS—occipital suture; OS—ocular suture; OSC—ocular sclerite; PRTL—parietal; PT--posterior tentorial pit; SGE:—subgena; ST—stipes; TB>-tentorial bridge; TL~tentorial lamella; VX—vertex.  12. the g a n g l i o n and o t h e r organs o f t h e head. to the t e n t o r i a l bridge.  The t e n t o r i a l b r i d g e i s  (HB), which i s  pit-like  l o c a t e d on each s i d e o f the o c c i p i t a l foramen, at  impressions  produced by  these points to form the b r i d g e .  t o t h e p o s t e r i o r t e n t o r i a l arms o f g e n e r a l i z e d i n s e c t s t o Snodgrass bridge,  (1935),  are  "continuous i n a transverse  through t h e back o f t h e  The d o r s a l a r m s a r e A. cestus they arise  just dorsad  ventrally  invaginations is  which,  homologous according  bar o r t e n t o r i a l  secondary outgrowths o f the a n t e r i o r arms.  In  j u s t a n t e r i o r to t h e t e n t o r i a l b r i d g e and pass  of the antennal The Head  The  It  posterior  head".  d o r s a l l y t o t h e c r a n i a l w a l l where t h e y a r e parietals  are  supported by them.  a s e m i - r i n g - l i k e b a r between t h e  ( F i g . 4, 5 P T ) , w h i c h a r e  of the exoskeleton  postero-dorsally  The v e n t r a l p a r t s o f t h e i r p o s t e r i o r h a l v e s  continuous w i t h the hypostomal bridge  tentorial pits  They e x t e n d  secondarily attached  antero-  to  the  sockets. Appendages  trophi. E x c e p t f o r some m o d i f i c a t i o n s i n t h e l a b i o - m a x i l l a r y c o m p l e x ,  mouth p a r t s o f A ^ c e s t u s a r e v e r y g e n e r a l i z e d . biting,  rasping,  and  They are adapted  for  lapping.  The l a b i u m ( F i g . 3, 6 L M ) i s  a moderately large  hinging on the v e n t r a l margin of the clypeus.  Its  flap-like  plate  e n t a l margin i s  o u s w i t h t h e membrane w h i c h f o r m s t h e r o o f o f t h e p r e o r a l c a v i t y . some i n s e c t s  continuIn  t h i s membrane b e a r s a s m a l l l o b e w h i c h h a n g s down i n t h e  o r a l c a v i t y , the epipharynx. but does not form a l o b e , epipharynx.  the  I n JU c e s t u s t h i s membrane i s  and, therefore,  cannot  pre-  cushion-like  r i g h t l y be c a l l e d  an  13. The m a n d i b l e s the b i t i n g  ( F i g . 2, 3, 5, 6 MD; 1 3 A , 1 3 B ,  13C) a r e t y p i c a l o f  jaws found i n t h e g e n e r a l i z e d group o f i n s e c t s .  they are  subtriangular  lated at  A and C o n t h e v e n t r a l m a r g i n o f t h e genae  D i s t a l l y they are  i n shape w i t h t h e base o f t h e t r i a n g l e  (Fig. 2 A, G). sub-  bidentate.  The l a b i o - m a x i l l a r y c o m p l e x ( F i g . 4 ) . labium and m a x i l l a e are  base  articu-  p o i n t e d , and bear on t h e i r p o s t e r i o r margins a  a p i c a l t o o t h making them  separate u n i t s ,  the margin o f the cranium, but i n JL optera,  At the  the postlabium i s  In generalized  and a r e  separately  c e s t u s , as  the  attached  i n the majority of  l a c k i n g , and t h e p r e l a b i u m i s  brane between t h e s t i p i t e s  insects  o f t h e two m a x i l l a e .  suspended  This c l o s e l y  to Hymen-  b y mem-  associates  t h e l a b i u m w i t h t h e m a x i l l a r y appendages and t h e r e b y forms a l a b i o - m a x i l l a r y complex. cardines  When t h i s u n i t i s  in  s i t u i t completely hides the maxillary  from v i e w .  The m a x i l l a e  ( F i g . 7, 8 ,  9) p o s s e s s a l l t h e p a r t s t y p i c a l o f  p r i m i t i v e insect ambulatory l i m b . part,  the cardo  articulates  at  stomal bridge,  (CD), and a d i s t a l p a r t , its  the stipes  and d i s t a l l y w i t h the s t i p e s .  t i o n with the labium.  it  gives  Like the cardo,  subgenae by ample membrane. a movable five-segmented  stipes i s  divided into a proximal (ST).  The  cardo  base w i t h a condyle on the g n a t h a l margin o f t h e hypo-  shaped i n s u c h a manner t h a t  l a r y p a l p has  The b a s e i s  the  palp  (MXPLP). part  i t i s attached  t i p , the  of the stipes; On i t s  is  associa-  l a t e r a l l y to  In generalized  i n t h i s manner.  s t i p e s b e a r s two movable f l e s h y l o b e s :  sclerite  the m a x i l l a a very close  L a t e r a l l y , near i t s  a p a l p i f e r which i s  not d i f f e r e n t i a t e d  The l a t t e r  stipes  insects in this  bears  the  maxil-  species  d i s t a l margin  an i n n e r lobe,  the  the l a c i n i a  the  the (LC);  14.  and an o u t e r l o b e , t h e g a l e a composite  ligula  (GA).  The l a b i u m ( F i g . 1 0 ,  11,  12),  as  s t a t e d above,  because i t bears a l l the l a b i a l appendages.  l a t e r a l margins,  are  t h e movable four-segmented  d i s t a l margin i s a large  fleshy lobe,  consists  strengthened  by a p a i r of  l a b i a l palps  sclerites  (LSC).  insects.  when i n s i t u ,  (LIG),  is  reinforced Its  a fleshy lobe.  base  is  ligula,  These  The d o r s a l  are surface  forms w i t h t h e l i g u l a a s m a l l s a l i v a r y  l o c a t e d the opening of the s a l i v a r y duct  pocket  (SLO).  antennae. The a n t e n n a e  like,  i n A^ cestus  many-segmented  articulates  antennal socket meter,  and are  (ASO).  2, 3 B S ;  segment  ( F i g . 1,  14A, 14B,  15)  (BS)  is  t h e longest  thread-  They average  large  and  bulbous.  3 AN) o n t h e l a t e r a l e d g e o f  The s e c o n d  segment o f a l l .  segment i s  c o n s i d e r e d t o be p r e s e n t  smaller  The f o l l o w i n g  smaller to the t i p of the antennae,  organ,  are  the  The f o l l o w i n g s e g m e n t s a r e much s m a l l e r i n d i a -  c y l i n d r i c a l i n shape.  become p r o g r e s s i v e l y Johnston's  The b a s a l  with a condyle  the t h i r d which i s  tus,  ( F i g . 1,  appendages on the f r o n t o f t h e h e a d .  41 segments f o r each s e x . It  It  On  continuous w i t h a hypopharyngeal l o b e , the hypopharynx  at the base of which i s The  (LBPIP).  On e a c h s i d e o f t h e is  single  t i p , on the  ligula  p r o b a b l y t h e p a r a g l o s s a e o f t h e more p r i m i t i v e i n s e c t s .  (HPH), w h i c h ,  a  generalized  w h i c h make i t a r a s p i n g o r g a n .  immediately posterior to these s c l e r i t e s ,  of the l i g u l a i s  of a  Near i t s  the composite  formed b y f u s i o n o f t h e g l o s s a e o f g e n e r a l i z e d by l i g h t l y - s c l e r o t i z e d ridges  the  organ.  p r e s u m e d b y t h e a u t h o r t o b e t h e p r e m e n t u m (PMT) o f  insects  its  closely associated with  ( L I G ) o f t h e l a b i u m when i n s i t u , a n d f o r m w i t h i t  b r u s h - l i k e r a s p i n g and l a p p i n g  part  These a r e  segments  A sensory  i n the second  than  appara-  segment o f  PLATE II  Fig, ?•  Ental aspect of l e f t maxilla (50x)«  Fig, 8,  Posterior aspect of l e f t maxilla (50x),  Fig, 9«  Lateral aspect of l e f t maxilla (50x).  Fig, 10,  Anterior aspect of labium (50x),  Fig, U ,  Posterior aspect of labium (50x),  Fig, 12,  Lateral aspect of labium (50x).  Fig, 13A,  Anterior aspect of l e f t mandible (50x)»  Fig, 33F»  Lateral aspect of l e f t mandible (50x).  Fig. 130, Fe-sterior aspect of l e f t mandible (50x), Fig, 14A, Lateral aspect of the fourteenth segment of the female antenna (50x), Fig, 14B, Lateral aspect of the fourteenth segment of the male antenna (50x), Fig, 15,  Cross-section of the twenty-second segment of the female antenna (50x),  A—mandibular acetabulum; C—mandibular condyle; CD—cardo; GA—galea; HPH—hypopharynx; LBPLP—labial palp; LC—lacinia; LIG—ligula; LSC— ligular sclerite; MXPLP —maxillary palp; PGL—paraglossa; PMT—prementum; ;  SLO—opening of the salivary duct; SO—sensory organ; SP —sensory p i t ; ;  ST—stipes.  15. nearly a l l insect^ is not present in /L cestus.  Each segment, except  the first and second, bears a series of sensory pits (Fig. 14A, 1AB SP) which have no set pattern.  These pits are much smaller and more plenti-  ful in the segments of the male antennae.  The eleventh to twenty-first  segments (Fig, 14B) of the male antennae bear an ellipitical-shaped organ (SO), probably sensory in function; it is from five to thirty times larger than the sensory pits on the male antennae. found in the female antennae.  None of these organs were  The segments of the female antennae from  the seventeenth to the end are flattened on the ventral side (Fig. 15). The sensory pits on this flattened surface are round and numerous. The Cervix The neck region of insects has been considered a separate body segment by some writers, but studies by Crarapton (1917) showed this to be impossible.  He pointed out that the neck region of insects is in every  way homologous with the other intersegmental regions between the true thoracic segments and, therefore, cannot represent a true body segment. The fact that ganglia or other segmental structures are not found in this region of known insects in the embryonic or imaginal stages seems proof enough that this is really an intersegmental region. To deduce otherwise would mean acceptance of the intersegmental regions between the pro-, meso-, and metathoraces as body segments. In A± cestus the neck is almost completely hidden from view by the overlapping prothorax.  However, when the head is pulled forward, the  cervix shows as a short, narrow, membranous region containing, laterally, prong-like sclerites (Fig. 19, 21, 22, 23 V) which are fused with the episternum of the prothorax.  These sclerites articulate anteriorly with  16. the occipital condyles of the head.  This articulation limits the head  to l i t t l e , i f any, movement in the horizontal plane. The Thorax The thorax of most Hymenoptera is highly modified in comparison with the generalized insect thorax.  In this respect i t is second only to the  Diptera in the evolutionary scale of development.  Many of the modifica-  tions that have occurred in the thorax of the Hymenoptera are demonstrated by the thorax of A. cestus, such as:  (1) the fusion of the first abdominal  segment with the metathorax, and its incorporation into the thoracic division of the body; (2) the separation of the pronotum from the propectus, and its close association with the front of the mesothorax; (3) the concealment of the mesopostnotum and its phragma by invagination within the thoracic cavity; (4) the reduction of the pro- and metathoraces caused by the enlargment of the mesothorax to accomodate the concenbation of power in it for prope/llsion of the fore- and hind-wings; (5) the formation of a single, Large mesopleural plate on each side of the mesothorax by the narrowing of the mesepimeron, and the incomplete suppression of the mesopleural suture; and (6) the formation of a prepectal plate in the mesothorax, cut off from the anterior parts of both the mesosternum and mesopleuron by the prepectal suture. The prothorax. In Aj_ cestus the prothorax is greatly reduced.  The pronotum (Fig.  16, 17, 18, 19, 20 N^) is closely associated with the mesothorax. Dorsally i t is a very narrow sclerite immediately anterior to the mesonotum (Fig. 25 N2); laterally i t broadens out and is extended towards the base of the wings.  Its posterior ventral angles curve ventrally and almost meet.  lateral prolongations practically make up the complete pleura of the  Its  PLATE: H I  F i g . 16•  Lateral aspect of thorax with head, abdomen, and thoracic appendages removed (17x).  F i g . 17.  Dorsal aspect of thorax with head, abdomen, and thoracic appendages removed (17x)»  F i g . 18.  Ventral aspect of thorax with head, abdomen, and thoracic appendages removed (17x).  EPS]_—proepisternum; PL3—metapleuronj  EPS2—mesoepisternum; NT_—pronotum;  PPCT—prepectus; S]_—prosternum;  N3—metanotum;  —mesosternum;  S3—metasternumj SCL2—mesoscutellumj SCT2—mesoscutumj TG—tegulaj V — c e r v i c a l s c l e r i t e ; I T — f i r s t abdominal tergum, or;?prdpod_um.  17 anterior region of the thorax.  The dorsal edge of the pronotum is  slightly folded inwards forming a kind of resting seat for the ventral margin of the mesonotum. This fold partially encircles the first thoracic spiracle (Fig. 19, 20 SP) which opens on the dorsal posterior comer of the pronotum. The propectus (Fig. 21, 22, 23) in Aj_ cestus is made up of the much reduced propleura (EPSj) and prosternum (S^) which together form a loose suspensorium for the prolegs.  It is loosely attached to the pronotum by  membrane. Each of the propleura consists of a single sclerite, the episternum, which reaches forward in the neck region to the base of the head. Each proepisternal "plate is curved mesally over the ventral surface of the prothorax so that the two almost meet along the mid-line in front of the prosternum.  In more generalized insects the propleura consist of two  plates, an anterior proepisternum and a posterior proepimerony which are divided by a pleural suture.  No such suture was located on the propleuron  of A., cestus, and, therefore, i t is assumed that the two sclerites have fused together solidly or that the proepimeron has been completely lost. A horizontal ridge divides the propleura into an upper and lower region, but this is not the pleural suture found in the more generalized forms. Anteriorly the propleura overlaps the neck region.  Internally, at this  region, they each present a shelf-like horizontal apodeme (Fig. 21 V), inflected from submarginal grooves on their outer surface.  Distally  these apodemes expand anteriorly and posteriorly in such a manner that they give, anteriorly, excellent articulatory surfaces for the occipital condyles of the head, and, posteriorly, an apodeme for attachment of prothoracic muscles.  This has evolved, according to Snodgrass (1935), from  PLATE I V  Fig.  19*  L a t e r a l aspect o f prothorax  Fig.  20.  D o r s a l aspect o f pronotum  Fig.  21.  D o r s a l aspect o f t h e propectus showing t h e prothoracic endostemum, and a r t i c u l a t i o n o f p r o p e c t u s w i t h t h e h e a d (25x).  Fig.  22.  V e n t r a l aspect o f t h e propectus  (25x).  Fig.  23.  L a t e r a l aspect o f t h e propectus  (25x).  Fig.  24«  D o r s a l a s p e c t o f t h e mesopectus w i t h meson o t u m r e m o v e d t o show t h e m e s o t h o r a c i c e n d o s t e r n u m (25x).  A — p l e u r a l apophysis; B—posterior apophysis arm  o f endostemum;  A]_—anterior apophysis of cervical sclerite;  CX^—prothoracic coxa;  DA—dorsal apophysis;  SP—thoracic  PR—pleural ridge;  spiracle;  WP—pleural wing  (25x).  o f t h e mesoendosternum; BS—basisternum;  G—anterior  D — l a t e r a l arm o f endosternum;  E P S ^ — p r o e p i s t e r n u m ; EPS2—mesoepisternum;  sternum; FU—furca o r endostemum; PPGT—prepectus;  (25x).  —pronotum; O C C — o c c i p i t a l S-j_—prosternum;  FS—furca. condyle;  S2—mesosternum;  V—cervical s c l e r i t e ; ¥ — l a t e r a l extension of  process.  furca;  2 4  18  a f u s i o n o f the neck s c l e r i t e s propleura.  In Snodgrass  The p r o s t e r n u m i s t h e f r o n t coxae  (CX3.)  (1942) i t  sclerite,  the basisternum  23)  i t consists  (BS),  the  apodeme.  sclerite  of an a n t e r i o r ,  and a p o s t e r i o r ,  The l a t t e r  is  a right-angle with the basisternum. elaborate  named t h e c e r v i c a l  to  lying  between  and b e h i n d t h e v e n t r a l p a r t s o f t h e e p i s t e r n a .  ( F i g . 21, 22,  (FS).  is  a small, triangular-shaped  A. cestus  the furcasternum  f o u n d i n more p r i m i t i v e i n s e c t s  triangular-shaped  oval-shaped  sclerite,  f o l d e d d o r s a l l y so t h a t It  is  endoskeleton of the prothorax i s  from t h i s  it  forms  s c l e r i t e that  developed.  In  These  the  sclerites  are b l a c k i n c o l o u r . The p r o t h o r a c i c e n d o s k e l e t o n s i s t s mainly of four parts:  ( F i g . 20,  2 1 , 23)  a p a i r o f d o r s a l phragmas,  p l e u r a l apodemes, and a s t e r n a l a p o p h y s i s . and occupies  d o r s a l phragmas  ( F i g . 2 0 DA) g i v e a t t a c h m e n t  (V) a r e  parts.  It  for tergopleural  p l e u r a l apophyses  muscles  (B)  The  f o r f u r t h e r muscle attachment.  i n c l u d e s a p a i r of l a t e r a l l y divergent wings, or  furcae,  u n i t e d i m m e d i a t e l y a n t e r i o r t o t h e p o s t e r i o r p l e u r a l apodemes (D) o v e r t h e c o x a l c a v i t y .  i o r l y producing another p a i r of apophyses  They are  The  endoskeletal  w h i c h e x t e n d t o t h e d o r s a l edge o f t h e p r o p l e u r o n t o w h i c h t h e y  The  The  ( F i g . 21 A ) .  i s much m o r e c o m p l i c a t e d t h a n t h e a b o v e  wings form a bridge  of  s l i g h t l y produced p o s t e r i o r l y , and form a  s e c o n d p a i r o f p l e u r a l apodemes s t e r n a l apophysis  two p a i r s  much o f t h e i n t e r i o r o f t h e p r o p e c t u s .  i n s e r t e d on t h e p o s t e r i o r  cervical sclerites  con-  T h e l a t t e r i s much l a r g e r  than the others  which are  i n Aj, cestus  are  (A).  extended  These anter-  (C).  pterothorax. This i s  the wing-bearing s e c t i o n of the t r u n k , and i n A . cestus  19. i s made up o f t h r e e body segments: the  t h e mesothorax, t h e metathorax, and  f i r s t abdominal segment o f o t h e r i n s e c t s .  These t h r e e segments a r e  i n t i m a t e l y u n i t e d t o f o r m a m e c h a n i c a l u n i t s u p p o r t i n g t h e wings, t h e m i d d l e and h i n d l e g s , and t h e abdomen. segment,  Between t h e t h i r d  pterothoracic  o r propodeum, and t h e abdomen, t h e r e i s a deep c o n s t r i c t i o n which  i s t y p i c a l o f t h e sub-order C l i s t o g a s t r a t o which t h i s s p e c i e s b e l o n g s . The dorsum o f t h e p t e r o t h o r a x i s e a s i l y d i f f e r e n t i a t e d i n t o i t s component p a r t s . 25 N2);  These a r e :  a l a r g e a n t e r i o r p l a t e , t h e mesonotum ( F i g .  a s m a l l , narrow p l a t e , t h e metanotum ( F i g .  quadrangular p l a t e , t h e propodeum, o r t r u e f i r s t 28 I T ) .  29 M^); and a b r o a d ,  abdominal tergum ( F i g .  The l a t t e r i s s o l i d l y a n c h y l o s e d w i t h t h e m e t a p l e u r a l  sclerites.  Unlike the dorsal surface, the s t e r n a l surface o f the pterothorax i s made up o f two p l a t e s : 27 S2);  a l a r g e a n t e r i o r p l a t e , t h e mesosternum ( F i g .  and a s m a l l e r p o s t e r i o r p l a t e , t h e metasternum  (Fig.  30 S 3 ) .  These a r e c o m p l e t e l y f u s e d w i t h t h e p l e u r a o f t h e i r r e s p e c t i v e  segments.  They a r e s e p a r a t e d f r o m each o t h e r b y a s u t u r e between t h e coxae o f t h e middle l e g s . in this  The sternum o f t h e f i r s t  abdominal segment has been  lost  species.  The p l e u r a o f t h e p t e r o t h o r a x c o n s i s t s o f two p a i r s o f s c l e r i t e s : l a r g e a n t e r i o r p a i r , t h e mesopleura ( F i g . 28 PL3).  ior  p a i r , the metapleura ( F i g .  the  sternum o f t h e i r r e s p e c t i v e segments.  t i n u o u s w i t h t h e f i r s t abdominal tergum.  25  EPS2);  and a s m a l l e r p o s t e r -  Both p a i r s a r e c o n t i n u o u s w i t h The l a t t e r p a i r a r e a l s o c o n T h i s p a i r , though c o n t i n u o u s  w i t h t h e f i r s t abdominal tergum and t h e metasternum, from them b y prominant r i d g e s .  a  are differentiated  20. The  mesothorax. This i s  t h e power-house  ment, and i t s  sclerotic  o f JL c e s t u s .  surfaces are  strength to hold the increased  It  is  the l a r g e s t body  correspondingly large.  power has  The m e s o n o t u m anterior-half two a r e a s :  of generalized  ( F i g . 25 N2)  e x t e r n a l l y covers  divisional fissure The l a t e r a l m a r g i n s  (TS)  is  (SCT2),  sclerites  surface.  a little  This part  more t h a n  is  (SCL2).  and t h e m e s o s c u t e l l u m  immediately behind a broad,  a b r u p t l y curved v e n t r a l l y .  the case of the scutum,  form, p o s t e r i o r l y , the n o t a l wing processes  (PNP) f o r t h e n o t a l a r t i c u l a t i o n o f t h e f i r s t  (APH2)  of the f i r s t  p a i r of wings.  and a narrow, a n t e r i o r ,  surfaces which,  and t h i r d  Anteriorly i t  The  deep f u r r o w on t h e  o f the scutum and t h e s c u t e l l u m are They p r e s e n t l a t e r a l  the  divided into  scutum./  sclerites  of  presen-  p o s t e r i o r margin of the  and  for  insects.  of the thoracic dorsal  t h e mesoscutum  The n e e d  necessitated close association  t h e a d j o i n i n g segments and f u s i o n o f t h e c l o s e l y - r e l a t e d t e d by the mesothorax  seg-  forms  l a t e r a l surface which i s  in  (ANP)  axillary the  prephragma  closely  associated  w i t h t h e d o r s a l i n f l e c t i o n o f t h e p r o n o t u m when i n s i t u .  The l a t e r a l  faces of the scutellum extend a n t e r i o r l y a  beyond the  short distance  surpost-  b  e r i o r e x t r e m i t y o f t h e scutum where t h e y proaden out l a t e r a l l y and f o r m s m a l l hoods which p a r t i a l l y c o v e r t h e b a s i s o f t h e h i n d - w i n g s These a p p e a r t o be t h e homologues of Diptera.  o f t h e i n n e r squamae f o u n d i n t h e  These l a t e r a l s u r f a c e s are  differentiated  surface of the s c u t e l l u m and the p o s t e r i o r which extends to near the p o s t e r i o r along the p o s t e r i o r margin of the ends b y t h e s e  ridges.  (Fig.  part  from the  scutum i s  thorax  dorsal  of the scutum by a  margin of the scutellum.  26).  ridge  The f u r r o w  abruptly terminated at  its  21.  The m e s o p o s t n o t u m attached  is  a semi-sclerotic  to the p o s t e r i o r margin of the scutellum.  a very large cavity.  ( F i g . 25, 26 PN2)  (PPH2)  postphragma  The l a t e r a l e x t r e m i t i e s  dorsal posterior  corners  which extends  far  It  p o s t n o t u m a n d t h e p o s t e r i o r phragma a r e  continuous  into the  of the postnotum are  o f t h e mesepimera  is  with  metathoracic  continuous with  the  (EPLlj) o f t h e m e s o p l e u r a .  The  completely invaginated i n t o the  t h o r a c i c c a v i t y , a n d a r e v i s i b l e o n l y when t h e m e t a t h o r a c i c removed f r o m t h e  surface  segment  meta-  is  mesothorax.  The m e s o p l e u r a  ( F i g . 16,  18,  17,  25, 26, 27 E P S 2 , E P M 2 ) a r e t h e  large  l a t e r a l p l a t e s o f the mesothorax continuous v e n t r a l l y w i t h the  sternum  (Fig.  27 82).  suture  (Fig.  25 P S ) i n t o a l a r g e a n t e r i o r s c l e r i t e , t h e e p i s t e r n u m  Each p l e u r o n i s  d i v i d e d by a sculptured p l e u r a l  (EPS2),  which  p r a c t i c a l l y makes u p t h e w h o l e o f t h e p l e u r o n , and a n a r r o w p o s t e r i o r sclerite,  the epimeron  produced d o r s a l l y ,  (EPM2).  The a n t e r o - d o r s a l  margin of the former  forming a broad p l e u r a l wing process  (WP) w h i c h  is  acts  as a f u l c r u m f o r the f r o n t - w i n g . The p r e p e c t u s  ( F i g . 16,  18,  24, 25, 27 PPGT ) i s t h e b r o a d  S2)* m e s e p i s t e r n a (EPS2),  between t h e mesosternum  ( F i g . 16  notum ( N j ) .  is  a p u r e l y secondary  It  is  tera  This plate  ( S n o d g r a s s 1911).  plate  and the  pro-  p r o d u c t i o n i n t h e Hymenop-  d i v i d e d from the former areas by a  sclerotic  ridge. The m e s o s t e r n u m  ( F i g . 16,  forming the broad undersurface  18,  24, 25,  27 S2)  of the mesothorax.  curved d o r s a l l y and forms a s m a l l s c l e r o t i c  is  the s c l e r o t i c  Posteriorly i t  region is  r e g i o n between the coxae  of  coith  the middle legs which are (Fig.  24).  synonymous te- t h e f u r c a s t e r n u m o f t h e  The s t e r n u m a n d p r e p e c t u s  prothorax  are d i v i d e d a l o n g t h e i r median  line  PLATE V  Fig. 25.  Lateral a s p e c t o f m e s o t h o r a x — a p p e n d a g e s r e m o v e d (25x).  Fig. 26.  Dorsal a s p e c t o f m e s o t h o r a x - t - a p p e n d a g e s , r e m o v e d (25x).  Fig. 27.  Ventral a s p e c t of m e s o t h o r a E X — a p p e n d a g e s r e m o v e d (25x)«  ANF —anterior n o t a l w i n g p r o c e s s ; APH2—mesothoraeic p r e p h r a g m a ; !  EPM2~mesoepimeron;  EPS2—mesoepisternum; N2—mesonotum;  c i c p o s t n o t u m ; PNP—posterior n o t a l w i n g p r o c e s s ;  PK2—mesothora-  PPCT—mesothoraeic  p r e p e c t u s ; PPH2—mesothoraeic p o s t p h r a g m a ; P S — p l e u r a l s u t u r e ; S2—mesos t e r n u m ; S G I g — m e s o s c u t e l l u m ; ' SGT2—mesoscutum; T G — t e g u l a ; suture; WP—pleural wing process.  TS—transverse  22. by a deep suture which marks the point of invagination of adjoining sclerites to form the large endostemum of the mesothorax. The endoskeleton of the mesothorax (Fig. 24, 25, 26, 27).  In A.  cestus the internal ridges formed by the transverse fissure (Fig. 26 TS), the pleural suture (Fig. 25 PS), the prephragma (Fig. 25, 27 postphragma (Fig. 25 , 26, 27  PPH2),  APH2),  the  and the endostemum (Fig. 24 FU) make  up the endoskeleton of the mesothorax.  The endostemum extends from the  prepectus to the posterior part of the mesosternum.  Immediately posterior  to its middle part i t is produced laterally into wing-like structures (Fig. 24 W) which extend to the pleura where they are attached in front of the pleural ridge (PR). The wings coalesce dorsally and extend anteriorly into an anterior median apophysis {Aj),  Between the dorsal coalescence  and the base an oval-shaped aperture is formed through which passes the ventral nerve cord. The ventral terminations of the pleural ridges extend into the coxal cavities and form articulatory condyles for the coxae of the mesothoracic legs. The metathorax (Fig. 16. 17. 18, 28, 29. 30)., In Aj_ cestus the metathorax, like the prothorax, is much reduced in size.  Its apparent functions are to present articulatory surfaces for  the hind-wings and hind legs, and to house the muscles used to move the latter.  Its pleura are fused dorsally with the notum of the first  CLboCominaJ  thoraeio segment which contains the second pair of thoracic spiracles (true first abdominal spiracles), and forms a cap over the posterior part of the thoraxe The metanotum (Fig. 28, 29 N3) is a very narrow, sculptured sclerite between the mesoscutellum and the propodeum. It bears on its lateral  23. extremities the anterior and posterior notal wing processes of the hindwings. The metapleuron (Fig. 28, 29, 30 PL-) is extensively modified and its sclerites show l i t t l e homology with those of the generalized insect wing-bearing thorax.  It is fused with both the metasternum (Fig. 30 S3)  and the propodeum (IT), forming with them a complete unit which composes the posterior third of the thorax.  Each pleuron is separated into a small  anterior triangular portion and a larger posterior part by a sculptured furrow which crosses the anterior margin of the propodeum and terminates at the lateral extremities of the metasternum.  The anterior portion is  extended dorsally to the metanotum (Fig. 29 N3). It bears the metapleural wing process (WP) which acts as a fulcrum for the hind-wings. The posterior part of the metapleuron bears a small condyle which extends into the coxal cavity of the hind leg for its articulation with the segment. The metasternum (Fig. 16, 18, 28, 30 S3) is the large ventral plate of the metathorax.  It is slightly concave anteriorly on each side of the  mid-line to accomodate the large coxae of the hind legs.  It extends to  - the posterior aperture of the thorax in which is inserted the abdominal petiole, or constricted second abdominal segment. The propodeum (Fig. 16, 17, 28, 29 IT) is a large, heavily-sculptured, convex plate covering the posterior part of the pterothorax.  Laterally  it contains the spiracles (Fig. 28, 29 ISP) of its segment.  Posteriorly with  it descends steeply to the abdominal petiole which articulates oa two internal condyles presented by the former.  On each side, at the top of  the descending slope, the propodeum is extended into prominent blunt spines.  Though this plate is commonly termed the propodeum, i t is really  P L A T E V/I  Figi  28.  L a t e r a l aspect of r e m o v e d (25x).  Fig.  29.  Dorsal aspect of r e m o v e d (25x).  Fig.  30.  Ventral aspect of r e m o v e d (25x).  FU—metaendosternum;  —metanotum;  metathorax—appendages  metathorax—appendages  metathorax—appendages  PL-—metapleuronj  WP^-pleural wing process; ISP*--first abdominal s p i r a c l e ; abdominal tergum,  I  or  propodeum.  —metasternum; IT—first  WP  WP  24. the propodeal tergum.  In the honey bee (Snodgrass 1942), the propodeal  sternum i s represented by a narow ventral plate behind the bases of the hind legs, but i n A. cestus the propodeal sternum appears to be lost or completely fused with the metasternal plate. The propodeal tergum of many Clistogastra i s divided into various areas which present sound morphological characteristics for species descriptions.  These areas are obscured by sculpturing i n Aj_ cestus, and are  therefore insignificant i n this species. The metathoracic endoskeleton (Fig. 30 FU) mainly consists of a pair of arch-like endosternal arms. They are broadened i n the middle, and attached laterally to a strong ridge which i s produced by the sculptured external furrow.  This furrow differentiates the propodeum and posterior  part of the metapleura from the metanotum and anterior part of the metapleura. The Legs The legs of  cestus are of the cursorial type. The metathoracic  legs are considerably larger than the prothoracic and mesothoraeic pair. The insect probably uses these legs to jump into the a i r prior to f l i g h t . Each leg (Fig. 34 to 36) i s made up of a basal segment, the coxa (Cx^, Cx£, CXj), a trochanter (TR), a femur (FM), a t i b i a (TB), and a tarsus (TAR).  Therefore, except for the basal subdivision of the femur (FM]_),  the legs of Aj_ cestus are very similar to those found i n generalized insects.  The tibiae of the prothoracic legs bear, distally, a large  movable spur, or calcar (Fig. 34 CC).  There are two such movable spurs on  each tibia of the meso- and metathoracic legs (Fig. 35, 36 CO). The tarsus of each leg i s five-segmented. case i s much larger than the following ones.  The f i r s t segment i n each On the end of the f i f t h  PLATE VII  Fig, 31, Ventral aspect of metathoracic pretarsus (50x), Fig, 32, Dorsal aspect of metathoracic pretarsus (5Qx), Fig, 33, Lateral aspect of metathoracic pretarsus (50x), Fig, 34, Anterior aspect of prothoracic leg (15-0. F i g , 35, Anterior aspect of mesothoracic leg (15x), Fig, 36, Anterior aspect of metathoracic leg (15x),  AR—arolium; CA—camera; CO:—calcar; GX^—prothoracic coxa ; CX —meso- 1  2  thoracic coxa; CX-j—metathoracic coxa; FM—femur; FM]_—basal segment of femur; OR—orbicula; TAR—tarsus; T B — t i b i a ; TR—trochanter; UN—ungues; UNG—unguitractor.  25. segment there are a number of sclerites, collectively termed the pretarsus. The pretarsus i s similar i n a l l six legs, and differs very l i t t l e , i f any, from that of the generalized insect.  It consists, essentially, of a pair  of large lateral claws, the ungues (Fig. 31, 32, 33 UN), and a median fleshy lobe, the arolium (AR). ends and are pointed.  The ungues are curved ventrally at their  They articulate dorsally with the last tarsal  segment, or last tarsomere. The arolium i s supported dorsally by a flask-shaped sclerite, the oricula (Fig. 32, 33 OR), and ventrally by a rectangular sclerite, the calcanea, or unguitractor (Fig. 31/33 UNG). Distally i t i s supported by an incomplete ring-like sclerite, the camera (Fig. 31 to 33 CA).  The terminology for the pretarsus was taken from  Bucher (1948). The leg articulations. The leg articulations are very similar to those of generalized insects.  Each coxa (Fig. 37 Cxp 38 0x2, 39 Cx^) i s articulated primar-  i l y with a pleural condyle which extends into the coxal cavity. In generalized insects, this condyle i s usually an extension of the pleural ridge formed by the pleural suture; however, i n  cestus the relation of  the pleural-coxal condyle to the lower end of the pleural ridge i s obscured in the pro- and metathoraces due to the modification of the pleural sclerites i n these segments. The meso- and metathoracic coxae are closely associated with the sterna of their respective segments, and their movements are almost completely restricted to an oblique transverse plane. This i s a secondary association which i s a specialization occurring i n the higher insects (Snodgrass 1935). The procoxae, on the other hand, are very loosely associated with the sterna of the prothorax, and their movements are not by any means as restricted as are those of the meso- and  PLATE VIII  Fig. 37. Dorsal aspect of coxopleural articulation of the prothoracic leg  (50x).  Fig. 38. Dorsal aspect of coxopleural articulation of the mesothoraeic leg (50x). Fig. 39. Dorsal aspect of coxopleural articulation of the metathoracic leg (50x). Fig. 40. Coxotrochanteral articulation of the l e f t prothoracic leg (50x). Fig. 41. Coxotrochanteral articulation of the l e f t mesothoraeic leg (50x). Fig. 42. Coxotrochanteral articulation of the l e f t metathoracic leg (50x). Fig. 43. Trochantero-femural articulation of the l e f t prothoracic leg  (50x).  Fig. 44. Trochantero-femural articulation of the l e f t mesothoraeic leg  (50x).  Fig. 45. Trochantero-femural articulation of the l e f t metathoracic leg  (50x).  Fig. 46. Tibio-femural articulation of the l e f t prothoracic leg (50x). Fig. 47. Tibio-femural articulation of the l e f t mesothoraeic leg (5Qx). Fig. 48. Tibio-femural articulation of the l e f t metathoracic leg (50x). Fig. 49. Tibio-tarsal articulation of the l e f t prothoracic leg (50x)« Fig. 50. Tibio-tarsal articulation of the l e f t mesothoraeic leg (50x), Fig. 51. Tibio-tarsal articulation of the l e f t metathoracic leg (50x).  CX]_—prothoracic coxa; CX2—mesothoraeic coxa; CX3—metathoracic coxa; EPSi—proepisternum;  EPS2—mesoepisternum; EPS3—metaepisternum; FM—femur;  FM^—basal segmentation of the femur; TAR—tarsus; T B — t i b i a ; TR—trochanter; J3l—posternum; S2—mesosternum; Sj—metasternum.  26. metathoracic coxae. The coxotrochanteral articulation of each leg i s dicondyiic (Fig. 40, 41, 42), and the movements at this joint are restricted to a perpendicular plane.  The trochantero-femoral joint (Fig. 43, 44, 45) of each leg i s  without any condylar articulation, and, though pliable i n a l l directions, i t s movements are very restricted.  The joints of the femur and t i b i a ,  and those of the t i b i a and tarsus are dicondyiic i n each leg (Fig. 46, 47,  48, 49, 50, 51). The Wings In insects the wing veins and the cells formed by them often present morphological characteristics which are of considerable importance i n the identification of species. In the past much work has been done on the wings and their veins.  One of the more important contributions made was  that of Comstock and Needham (1898-1899). Adopting the terminology of Redtenbacher, they developed a venational nomenclature that i s s t i l l widely used for naming the veins of most insect wings. At the same time, they devised a hypothetical wing from studies of wing tracheae which precede and, i n a general sense, determine the courses of the veins. This was to represent the primitive insect wing. Since them considerable contention has arisen concerning the correctness of the Comstock-Needham interpretation of the primitive wing. From Imms (1937) we note that Tillyard questioned the Comstock-Needham interpretation of the cubital vein, and from ontogenetical studies he concluded that this vein originally had three branches instead of two as was concluded by the former authors.  Snodgrass (1935) from studies  of wing veins and their associations with the axillary sclerites concluded that the Comstock-Needham f i r s t anal vein was really the post cubitus. Furthermore, we note that studies of Lamere i n 1922 upheld the views of  27. Redtenbacher concerning t h e f a c t t i v e l y a l t e r n a t e d as  that the main veins of i n s e c t wings  convex and concave v e i n s ,  a deduction formerly  primidismissed  by Comstock and Needham. The w i n g s o f t h e Hymenoptera a r e those of generalized i n s e c t s .  h i g h l y modified i n comparison  The f i r s t  with  a t t e m p t s made t o h o m o l o g i z e  the  w i n g v e i n s o f t h i s o r d e r w i t h t h o s e o f more p r i m i t i v e a n d g e n e r a l i z e d were t h o s e o f M a c G i l l i v r a y  (1906) a n d C o m s t o c k (1917). T h e i r u s e o f t h e  Comstock-Needham system r e s u l t e d i n a r t i f i c i a l some a n d u n s a t i s f a c t o r y  f o r use  analogies  which were  by hymenopteran s y s t e m a t i s t s ,  cumber-  A more a p p l i -  c a b l e n o m e n c l a t u r e was d e v e l o p e d b y R o h w e r a n d G a h a n (1916), b u t i t , is artificial,  orders  and though w i d e l y used does n o t h e l p p r e s e n t  too,  systematists  c o n s t r u c t n a t u r a l keys f o r proper c l a s s i f i c a t i o n o f the Hymenoptera,  to  Forbes  (1925) a t t e m p t e d t o c o r r e l a t e t h e d e v e l o p m e n t o f t h e h y m e n o p t e r a n w i n g v e i n s w i t h those of the C o l e o p t e r a , but h i s c o n c l u s i o n s , and Needham, a r e  based on t h e s t u d i e s  l i k e those of  of wing tracheae,  and are  Comstock considered  problematic. A recent  study on the homologies of the wing v e i n s of the  (Tenthredinidae)  by Ross  long-known p r i n c i p l e s , the convex-concave  (1936) h a s r e s u l t e d i n a g e n e r a l a c c e p t a n c e o f Ross based h i s s t u d i e s  on:  a l t e r n a t i o n of the main v e i n s  wing, a p r i n c i p l e advocated  by Redtenbacher  (1) t h e s i g n i f i c a n c e  affinities  by Snodgrass  (1935),  i n 1886;  and  (2) t h e  associa-  of the wings,  a  T h u s he was a b l e t o show d i s t i n c t  between t h e w i n g s and v e i n s o f t h e Hymenoptera and t h o s e o f  M e c o p t e r o i d and Panorpdd o r d e r s , and T r i c h o p t e r a .  The a s s o c i a t i o n  of  i n the p r i m i t i v e insect  t i o n of the main wing v e i n s with the a x i l l a r y s c l e r i t e s p r i n c i p l e advocated  sawflies  especially the Megaloptera,  Mecoptera,  o f t h e Hymenoptera w i t h t h e s e o r d e r s  based on t h e P a n o r p o i d Complex o f T i l l y a r d .  the  Using these p r i n c i p l e s ,  was  28.  wings a n d v e i n s o f  R o s s c o n s t r u c t e d a new h y p o t h e t i c a l w i n g w i t h w h i c h t h e t h e m o d e r n H y m e n o p t e r a c a n e a s i l y be h o m o l o g i z e d .  T h i s new i n t e r p r e t a t i o n  o f t h e p r i m i t i v e - t y p e hymenopteran  wing i s g a i n i n g more a n d more r e c o g n i -  t i o n i n the f i e l d  The v e n a t i o n a l n o m e n c l a t u r e  of systematics.  by Ross has r e c e n t l y been used by  Riegel (1948) i n h i s i n t e r p r e t a t i o n o f  the wing v e i n s o f c e r t a i n hymenopteran i n s e c t s family.  The p r e s e n t  author,  belonging to the  l i k e R i e g e l , has adopted  i n h i s i n t e r p r e t a t i o n of the wing veins of The f o r e - w i n g ( F i g .  developed  Ross's  Braconidae  nomenclature  cestus.  52A).  I n o r d e r t o h o m o l o g i z e t h e w i n g v e i n s o f A^ c e s t u s w i t h t h o s e o f h y p o t h e t i c a l wing developed by Ross,  we m u s t a s s u m e t h a t  m i g r a t i o n and subsequent f u s i n g o f v e i n s has o c c u r r e d . the cross-veins  considerable In the f r o n t  The r a d i u s  forming a strong,  56 S C ) a n d t h e s t i g m a  represented  its  r e d u c e d t o t w o (1A, two:  r a d i u s one  base w i t h the r a d i u s . 2A).  of the wing.  costa,  scale  ( F i g . 53  been to  c u b i t a l v e i n has f u s e d (M •  The a n a l v e i n s have  (M).  (RS).  been  The b r a n c h e s o f  The m i d d l e p a r t  with  Cu^) w h i c h  The b r a n c h e s o f t h e r a d i u s h a v e b e e n r e d u c e d  i n t o one v e i n  (C + R) a n d p r o d u c e s  them  The s u b c o s t a l v e i n h a s  produced a heavy median v e i n  m i g r a t e d a n t e r i o r l y i n s u c h a way t h a t  (M + Ouj),  The f i r s t  (R]_), a n d t h e r a d i a l s e c t o r  media are a l l fused  vein  (C + R ) .  by the large basal  ( F i g . 52A S T ) .  t h e base o f t h e media and has continuous at  the  has m i g r a t e d a n t e r i o r l y and f u s e d w i t h t h e  broad marginal v e i n  g r e a t l y r e d u c e d , and i s  is  wing  have been so a r r a n g e d t h a t t h e y a d e q u a t e l y c o u n t e r a c t  backward f o r c e p l a c e d on them b y t h e attachment o f t h e h i n d - w i n g t o by the h a m u l i .  the  to  the  of this vein  has  i t unites with the strong marginal  a l o n g c r o s s - v e i n between i t and t h e median v e i n  The d i s t a l p a r t o f t h e m e d i a c o n t i n u e s t o t h e d i s t a l m a r g i n o f It  i s connected t o t h e r a d i a l s e c t o r by two  cross-veins  29, (1R-M) and (2R-M) which enclose a small c e l l characteristic of the Ichneumonid fore-wing.  The cubital vein i s represented by i t s anterior branch  only (Cu^), the base of which forms with the base of the media (M) the heavy median vein (H t Cu ).  After branching from this vein, i t i s branched  into two subsidiary branches (Cu-ja) and (Cu^b). The former continues to the distal margin of the wing.  It i s parallel to the distal part of the  median vein (M), and i s connected to i t by the cross-vein (2M-Cu). The second branch (Cu^b) forms a cross-vein between the distal end of the f i r s t anal vein and Cu^.  Cu^ i s united to the d i s t a l part of the median vein by  the cross-vein (lM-Cu). A second cross-vein (Cu-A), between Cu-^ and the f i r s t anal (1A), i s almost continuous with the middle part of the median vein, and the two form a long cross-vein between the marginal vein (C * R) and the f i r s t anal vein (1A). This undoubtedly strengthens this part of the wing so i t can bear the strain placed on i t by the attachment of the hind-wing in this area.  The posterior margin of the fore-wing i s heavily  sclerotized to accomodate the connecting mechanism of the hind-wing, the hamuli. The hind-wing (Fig, 52A). The changes that occurred in the primitive-type wing to produce the hind-wing of Aj_ cestus are essentially the same as those that occurred in the production of the fore-wing.  The main differences are:  (1) the  radial and costal veins are united for a short distance at their bases; (2) the median vein (M) i s continuous with the distal margin of the wing, and i t is not connected to the marginal vein and has no association with i t ; (3) only one cross-vein (R-M)  i s present between the radial sector (RS) and  the median vein (M); (4) cubitus one (Cu-^) i s unbranched and i s connected to the f i r s t anal vein (1A) by the cross-vein (Cu-A); and (5) on the base  30, of radius one  (R^) are located the hamuli (Fig. 52A,  52B  HAM),  a row  of  large, posteriorly-curved spines which hold the hind- and fore-wings together during f l i g h t . The axillary sclerites (Fig. 53 to  56).  These are the sclerites found at the base of a l l insect wings. They facilitate the upward, downward, and rotating wing motions by presenting satisfactory articulatory surfaces for these various movements. These sclerites are collectively known as the pteralia (Snodgrass 1935). In Aj_ cestus the pteralia of each fore-wing consists of: axillary sclerites; and  (1)  three  (2) a median plate.  The f i r s t axillary sclerite (Fig, 52 1AX)  i s the anterior hinge  plate of the wing base. Its body i s supported by the anterior notal wing process of the mesonotum (Fig, 25 ANP), arm,  It extends anteriorly as a slender  and articulates with a humeral complex (Fig. 53) formed by the fusion  of the costal (C), subcostal (SC), radial (R), and medial (M) veins, and the median plate (M-^). It i s associated with the costal region of this complex. The second axillary (Fig. 53,  54 2AX) i s the vertical sclerite  articulating with the outer margin of the f i r s t axillary. rotates on the f u l c r a l wing process (Fig. 54 WP)  Ventrally i t  of the pleuron, and  dorsally i t i s flexibly attached to the radial section of the humeral complex.  To this sclerite i s attached a small sclerite (Fig. 53 AXD)  which  accomodates the insertion of muscles. The third axillary (Fig. 53, 54 3AX) i s an elongate sclerite articulating ventrally with the posterior end of the second axillary. end i s associated with the anal veins (1A,  2A),  Its d i s t a l  and i t s proximal end  articulates with the posterior notal wing process (Fig, 25  PNP),  31. Immediately anterior to the pleural wing process i s located a free pleural sclerite (Fig. 54 P) which i s associated with the axillary complex. Ventrally i t bears a small disk for muscle attachment. refers to this sclerite as the parapteron.  Snodgrass (1911)  It i s homologous with the  basalare sclerite of generalized insects (Snodgrass 1935). A large scale-like lobe i s flexibly attached to the scutum immediately anterior to the wing.  This i s the tegula (Fig. 25 TG).  It overlaps the  base of the wing. The pteralia of the hind-wings (Fig. 55, 56), like that of the front, consist of three axillary sclerites and a median plate.  No true tegula  is present, but the lateral margins of the mesoscutellum are expanded i n such a manner that they secondarily form a hood-like structure over the base of the hind-wings. The f i r s t axillary sclerite (LAX) articulates bodily with the anterior notal wing process of the metanotum. Anteriorly i t articulates with the sub-costal region of the axillary complex formed by the costal (C), subcostal (SC), and radial (R) veins.  The median vein (M) and median plate  (M^) are not part of the axillary complex of this wing. The second axillary sclerite (2AX)  articulates with the posterior  margin of the f i r s t axillary sclerite, and the metapleural wing process (Fig. 56 WP).  Dorsally i t i s flexibly fused with the radial region of the  axillary complex. It bears a small axillary disk (Fig. 55 AXD) used for muscle attachment. The third axillary sclerite (Fig. 55, 56 3AX) i s an elongate sclerite associated distally with the anal veins (1A, 2A).  Proximally i t articulates  with the posterior notal wing process of the metanotum, and with the  ELATE DC  Fig.  52A.  Fig.  52B.  Dorsal aspect of the l e f t  (15x).  f o r e - and hind-wings  Dorsal aspect of the hamuli of the l e f t  hind-wing  (5Cx). (25x).  Fig.  53.  Dorsal aspect of the l e f t mesothoraeic wing a r t i c u l a t i o n  Fig.  54.  L a t e r a l aspect of the l e f t mesothoraeic wing a r t i c u l a t i o n  Fig.  55.  Dorsal aspect of the l e f t metathoracic  Fig.  56.  L a t e r a l aspect of the l e f t metathoracic  Wing  (25x). (35x).  wing a r t i c u l a t i o n  (35x).  wing a r t i c u l a t i o n  veins.  1 A — f i r s t a n a l v e i n ; 2A—second a n a l v e i n ; C — c o s t a l  vein; C t  R—costal  v e i n plus the r a d i a l v e i n ; Cu-^—first branch of the c u b i t a l v e i n ; subsidiary  b r a n c h o f Cu-^; C u - ^ — s e c o n d  v e i n b e t w e e n C u a n d 1A; plus the f i r s t  subsidiary  branch of Cu^;  Cu-A—cross  HAM—hamuli; M — m e d i a l : v e i n ; M • Cu-^—medial v e i n  branch of the c u b i t a l v e i n ; I M - C u — f i r s t cross v e i n  m e d i a l v e i n and t h e f i r s t  between  b r a n c h o f t h e c u b i t a l v e i n ; 2M-Cu—second c r o s s  v e i n between t h e medius and t h e f i r s t  branch of the c u b i t a l v e i n ;  vein;  RS—radial sector;  R^—first  Cu-j^—first  branch of the radius;  R—radial  1R-M—first  v e i n b e t w e e n r a d i a l s e c t o r a n d m e d i a l v e i n ; 2R-M—second c r o s s v e i n r a d i a l s e c t o r and m e d i a l v e i n ; SC—subcosta;  Axillary  cross between  ST—stigma.  articulations.  1AX—first a x i l l a r y s c l e r i t e ; axillary sclerite; P^—parapteron;  2AX—second a x i l l a r y s c l e r i t e ;  AXC—axillary cord; AXD—axillary disk;  PD—disk of parapteron;  3AX—third  M-^—median  WP—pleural wing process.  plate;  32. posterior end of the second axillary sclerite. The parapteron (P) i s identical with the parapteron of the fore-wing, and i s associated with the anterior margin of the axillary complex. It also bears a disk (PD) for muscle attachment. The Abdomen The abdomen i s the portion of the insect body which contains the major viscera and the anal and genital openings. Furthermore, i t i s the chief part of the body producing movements of respiration.  Generally i t  has ten to eleven segments i n the imago stage, but this i s not always constant.  From embryological evidence i t has been concluded that the  abdomen of the most primitive insect originally had twelve segments, but through specialization and modification the modern insect has anywhere from six to eleven segments. For descriptive purposes the author has divided the abdomen of A. cestus i n the following manner: the pregenital or visceral segments, the genital segments, and the postgenital segments. The pregenital segments. In iU cestus there are eight pregenital segments i n the male, and seven i n the female. The f i r s t segment (Fig. 16, 17, 28, 29 IT) has migrated anteriorly and forms the propodeal, or middle segment of the body. The sternum of this segment has been lost or has coalesced with the metathoracic sternum. The second (Fig. 57, 58 11T) i s a petiole-like segment, much constricted at i t s base where i t i s abruptly elbowed dorsally.  Near i t s  posterior margin i t i s almost as broad as the rest of the body and i s  33. elbowed posteriorly.  The constriction and bending of this segment gives  the abdomen a petiolate appearance. Unlike the sclerites of the generalized abdominal segments, the tergum (11T) and sternum (11S) of this segment are fused, and are differentiated by incomplete lateral sutures which terminate before reaching the base of the segment.  On the lateral margins  of the tergum at the posterior elbow are located the second aMominal spiracles.  The location of these spiracles are significant morphological  characters used by present-day hymenopterists i n the construction of keys to Ichneumonid genera. The base of this segment bears three bulbous condyles, one dorsal and two lateral, which articulate with the propodeal condyles extending into the posterior thoracic aperture. The third, fourth, f i f t h , sixth, and seventh abdominal segments of both sexes are very similar i n size and shape. Each has a broad tergum (HIT, 1VT, VT, V1T, V11T) which i s continuous with a semi-sclerotic sternum (HIS, 1VS, VS, VIS, V11S). The latter, which i s much softer and more pliable than the tergum, shows signs of having lateral divisions which are the homologues of the pleural sclerites of the primitive insect segment.  The terga of the pregenital segments and that of the  eighth segment each bear a pair of spiracles near their lateral margins. The majority of these are hidden due to an increased telescoping of the posterior segments.  Near the anterior margin of the third tergum  (HIT) i s located a pair of broad, deep, oblique quadrate p i t s .  The  anterior margin of the fourth abdominal tergum bears a broad black band which i s used to help identify this species from i t s close relatives.  In the series of specimens examined by the author this band  was absent i n some teneral males.  This may be due to colour variation  34. caused by environmental f a c t o r s which are  The g e n i t a l  t h e a b d o m i n a l segments w h i c h a r e  in  f o r t h e male  composite  I n t h e male  genitalia  structures  is  of t h i s  generalized  The p o s t g e n i t a l  segments  form the p r i n c i p a l copula-  The f e m a l e  genitalia  from the e i g h t h and n i n t h  r e s p e c t t h e g e n i t a l segments o f  cestus are  membrane  (Fig.  57,  5$ I X a n d X T ) ,  are  syntergum as  d e f i n e d by Peck  I n t h e membrane oval-shaped  (1937).  I n the female a small  perhaps t h e remnant  (SOC) w h i c h a r e  insects.  much  fused w i t h the n i n t h tergum  These a r e  the  of the  the  tenth segment  homologues  excellent  and  semi-sclero-  between the tergum and sternum of t h i s  appendages  of the lepidopterous  postgenital  This i s  segments  a b s e n t , and t h e former i s  i m m e d i a t e l y v e n t r a l t o t h e a n a l a p e r t u r e has  located  socii  is  I n both sexes the t e n t h tergum i s  t i z e d area which bears setae. sternum.  of  insects.  I n Aj_ c e s t u s . t h e l a t t e r  forms w i t h i t a  segments.  s i m i l a r to those  These g e n e r a l l y i n c l u d e t h e t e n t h and e l e v e n t h a b d o m i n a l when p r e s e n t .  the  s p e c i e s t h e o n l y segment  the n i n t h .  which develop  the m a j o r i t y of  reduced.  insects  closely associated with  T h e i r appendages and outgrowths  t o r y organs of both sexes.  In t h i s  pigmentation  light  segments.  openings.  responsible  h u m i d i t y , and  1939).  These a r e  are  temperature,  i n f l u e n t i a l during the production of  (Wigglesworth  genital  such as  landmarks  of  the  for  the  t h e c o p u l a t o r y organs o f t h e male  and  segments. The G e n i t a l i a  As p o i n t e d o u t a b o v e , t h e s e a r e female which are V11S, V111S;  developed  from the  genital  F i g . 58 V H T , V 1 1 1 T , V 1 1 S ) .  segments  Considerable  (Fig.  57 V 1 1 T , V 1 1 1 T ,  harmony  exists  35. among authors concerning the development of the female genitalia, but discord and controversy have developed over the evolution of the male genitalia.  The present author has followed the work of Snodgrass (1935)  in his discussion of the female organs, and that of Peck (1937) in the discussion of the male organs. The female genitalia. From studies by Snodgrass (1935) fairly good evidence substantiates his conclusion as the the derivation of the female genitalia.  In most  pterygote insects the ovipositor shaft, sheath, and basal apparatus are apparent derivatives of the primitive insect gonopophyses, styli, and coxopodites of the genital segments. The female genitalia (Fig. 59, 60) of Aj. cestus consists of a long ovipositor attached to a basal apparatus and enclosed in an ovipositor sheath. The ovipositor is an elongate shaft composed of a ventral and dorsal pair of valvulae (1VL, 2VL) which are homologous to the gonopophyses of primitive insects.  The dorsal valves are fused in a single shaft which  is united to the ventral pair by a tongue-and-groove system (Fig. 60). There are two channels formed by these shafts, the lower being the egg tube (ET). The apex of the ovipositor is lance-shaped, and bears strong lateral serrate ridges for penetration of the host skin. the second  valvulae  The base of  bears a large knob-shaped median process (Fig. 59 RP)  called the rotary process by Bucher (1948).  The bases of the first  and second valvulae a r e attached by rami (Rl, R2) to the basal apparatus. The  rami  of the first valvulae  muscle attachment.  bear a  pair of  The basal apparatus  apophyses  (A) for  36. consists  of a p a i r of  small triangular plates  (1VLF) a r t i c u l a t e d by t h e i r  p o s t e r i o r v e n t r a l c o r n e r s t o a second p a i r o f elongate by  t h e i r p o s t e r i o r d o r s a l corners to the n i n t h tergum.  termed the f i r s t  second v a l v i f e r s are which enclose  generalized insects,  They a r e  posteriorly into sheath-like  and second v a l v u l a e . and are  and are  homoloThe  valvulae  These a r e t h e t h i r d  derivatives of the s t y l i of the  valvulae  coxopodites.  sensory i n f u n c t i o n .  The s t e r n a g e n i t a l i a are (Fig,  and are  o f t h e p r i m i t i v e e i g h t h and n i n t h segments.  elongated  the f i r s t  (2VLF),  These p l a t e s  (1935),  and second v a l v i f e r s by Snodgrass  gous t o t h e c o x o p o d i t e s  of  plates  o f t h e e i g h t h and n i n t h segments, f r o m w h i c h t h e  derived, are absent.  The s t e r n u m o f t h e s e v e n t h  58 V U L S ) f o r m s a s u b - g e n i t a l p l a t e .  (V111T) i s  The n i n t h t e r g u m ( I X a n d X T ) i s  tergum, and t h e two a r e  segment  The t e r g u m o f t h e e i g h t h segment  e l o n g a t e d v e n t r a l l y and forms a semi-sheath  abdominal p a r t s .  female  f o r the  coalesced  c l o s e l y a s s o c i a t e d w i t h the female  following  with the  tenth  copulatory  apparatus. The m a l e In  genitalia. insects  t h e male gonopore,  or g e n i t a l opening, i s  a s s o c i a t e d w i t h t h e n i n t h a b d o m i n a l segment w h i c h i s for  directly  responsible  a p p e a r t o be i n s t r o n g d i s a g r e e m e n t  concerning  t h e f o r m a t i o n o f the r e s u l t i n g male Authoritative authors  t h e e x a c t e v o l u t i o n a r y development as  a result,  genitalia.  o f t h e hymenopteran male organs,  a v a r i e t y o f t e r m i n o l o g y has a p p e a r e d .  c o n t r o v e r s i a l papers on t h i s t o p i c are  (1941)•  generally  those o f Peck  The t w o m o s t p r o n i i n e n t  (1937)  Peck upholds t h e t h e o r y t h a t t h e male organs o f t h e  e s p e c i a l l y those o f the Ichneumonidae, are  and,  and  Snodgrass  Hymenoptera,  derivatives of the p r i m i t i v e  37. coxopodite appendages.  Snodgrass, on t h e o t h e r hand, h o l d s t o  o r i g i n a l t h e o r y (1935) t h a t t h e male c o p u l a t o r y o r g a n s i n t h e d e v e l o p f r o m t h e c o n j u n c t i v a l membrane b e t w e e n t h e s t e r n a and n i n t h segments. conclusions,  but,  Both w r i t e r s give  because the evidence i s  mains i n a c o n t r o v e r s i a l  cestus belongs,  t e r m i n o l o g y , and u n t i l current theories,  it is  t e r a n male g e n i t a l i a .  various  of the  evidence  for  the author finds  f u r t h e r evidence impossible  cestus i s  is  their  Ichneumonidae,  the  family  i t convenient to adopt  given to  disprove  his  one o f  these  t o s t a t e the homologies  of the  hymenop-  the -following discussion  of the  male  p u r e l y a naming and d e s c r i p t i o n o f  the  parts.  I n t h i s s p e c i e s t h e male g e n i t a l i a main p a r t s : claspers,  a basal ring,  (Fig. 6l,  62)  an outer p a i r of c l a s p e r s ,  and an i n t r o m i t t e n t  The b a s a l r i n g ,  is  composed  elongate s c l e r i t e s gonocardo.  attached  (GC), i s  loosely attached  o r gonoforceps  (Fig. 6l,  and a r e  intromittent organ,  of  b y membrane  62 G F ) , a r e  (Fig.  continuous/membrane  the aedeagus  (AED).  te the dorsal  of  57  broad  b y membrane t o t h e p o s t e r i o r m a r g i n o f  Dorsally they coalesce along the a n t e r i o r part  dorsal margins,  four  organ.  o r gonocardo  The o u t e r c l a s p e r s ,  of  an i n n e r p a i r  t o t h e n i n t h segment i m m e d i a t e l y p o s t e r i o r t o t h e g e n i t a l p l a t e 1XS).  eighth  c o n t r a d i c t o r y , the problem r e -  h i s study to the  Therefore,  copulatory organs i n  Hymenoptera  state.  Because Peck r e s t r i c t e d to which  substantial  his  the  their  surface of  the  Their anterior ventral angles i  are  e x t e n d e d a n t e r i o r l y t o f o r m a p a i r o f a p o p h y s e s , t h e g o n o s t i p : L a l arms  (GSTA), f o r muscle attachment. gonoforceps  are  I m m e d i a t e l y p o s t e r i o r t o t h e s e arms  continuous with the inner c l a s p e r s ,  the b a s i v o l s e l l a  the (BV).  38.  These are broad plates which are invaginated into the interior cavity formed by the outer claspers.  Their dorsal margins are reinforced by  a heavy sclerotic bar, the basivolsellar strut (VSTR) which prevents bending of the basivolsella during copulatory activities.  Distally the  basivolsella bears a pair of hook-like sclerites used to grasp and hold taut the conjunctival membrane of the female so that the aedeagus can be inserted into the female gonopore and retained there.  The more dorsal  sclerite, the gonalacinia (GL), i s a separate unit which articulates on the posterior dorsal angle of the basivolsella.  The ventral sclerite, the  distivolsella (DV), i s an elongation of the posterior ventral margin of the basivolsella curved back on i t s e l f giving i t a hood-like appearance. The intromittent organ, or aedeagus (AED), consists of a pair of elongate bars connected by membrane to the dorsal margins of the gonoforceps and dorsal margins of the basivolsella.  Dorsally they are conti-  nuous for the most part, and ventrally they coalesce at their bases. Distally they curve ventrally and are slightly expanded. Anteriorly they extend far into the body cavity as a pair of apophyses (Fig. 6 l APA) for muscle attachment.  A pair of lateral extensions, the ergots (ERG), at the  base of these apophyses, serve as pivots for the intromittent organ during coition.  PLATE X  A—apodeme  Fig*  57.  L a t e r a l a s p e c t o f t h e male  Fig.  58.  L a t e r a l aspect o f the female  Fig.  59.  Longitudinal section of the genitalia.  female  Fig.  60.  Cross  ovipositor.  Fig.  61.  L o n g i t u d i n a l s e c t i o n o f t h e male talia.  Fig.  62.  V e n t r a l a s p e c t o f t h e male  of the f i r s t  abdomen.  s e c t i o n o f the female  valvulaj  AED—aedeagus;  abdomen.  geni-  genitalia.  APA:—apophysis o f  aedeagusj B V — b a s i v o l s e l L a ; D V — d i s t o v o l s e l l a ; ERG—ergot of the ET—egg t u b e ;  GC—gonocardo;  GF—gonoforceps;  s t i p i a l arm; R^—rami o f the f i r s t RP~rotary process;  the aedeagusj  G L — g o n o l a c i n i a ; GSTA:—gono-  v a l v u l a ; S2—rami o f t h e second  11S, I l l s , 1VS, V S , V I S , V11S, V111S,  valvula;  1XS—secohd,third, SOC--socii;  fourth,  fifth,  s i x t h , seventh,  e i g h t h , and n i n t h abdominal s t e r n a ; / L I T ,  1VT, V T , V1T, V11T, V111T, 1XT, X T — s e c o n d , t h i r d ,  fourth, fifth,  seventh,  1VL—first valvula;  eighth, ninth,  and t e n t h abdominal t e r g a ;  second v a l v u l a ; 3 V L — t h i r d v a l v u l a ; 1VLF—first valvifer;  VSTR—basivolsellar  strut.  valvifer;  111T,  sixth,  2VLF—second  2VL—  39.  Summary The author has made a study of the external anatomy of Aoplus cestus (Cresson), an Ichneumonid parasite of the oak looper, Lambdina somniaria (Hulst), and of the hemlock looper, lambdina f i s c e l l a r i a lugubrosa (Hulst), The various parts are described, and where possible an attempt has been made to homologize them with the parts of more generalized and primitive insects.  A detailed description i s given of:  (1) the exoskeleton and  endoskeleton of the head and i t s appendages; (2) the exoskeleton and endoskeleton of the three thoracic segments; (3) the abdomen; (4) the legs; (5) the wings and axillary sclerites; and (6) the male and female genitalia. Sixty-two illustrations accompany the text.  40 Literature  B r o w n , W. J.  Cited  The R o l e o f M o r p h o l o g y i n S y s t e m a t i c s .  1949.  Can. E n t .  82(12): 299-303. Bucher, G. E .  The Anatomy o f Monodontomerus d e n t i p i s B o h . ,  1948.  Entomophagous C h a l c i d . Comstock,  J. H . , a n d A . B . C o m s t o c k .  Insects. Comstock, Nat.  J. H . , a n d J . G . N e e d h a m .  J. H .  1898.  The W i n g s o f  Insects.  Am.  1899.  The W i n g s o f I n s e c t s ,  Am.  An I n t r o d u c t i o n t o E n t o m o l o g y .  1936.  Crampton, G . C. ites.  1917.  Trans. E. T.  Pacific  Ithaca,  Am. E n t . S o c .  Pis.  Ichneumonidae,  C h i e f l y from the  University Publications. Forbes, T. M. Soc.  Imms, A . D . Churchill, MacGillivray,  Ser.  Biol.  Sci.  Stanford  5(3): 101-269.  The H y p o t h e t i c a l W i n g o f t h e H y m e n o p t e r a .  1925.  Am.  Univ.  Proc.  (Description.)  P r i n c i p l e s of Systematic Entomology.  1928.  Scler-  10-17.  Slope o f t h e U n i t e d S t a t e s and B r i t i s h N o r t h A m e r i c a .  G. F.  Revised.  N. Y.  52: 199-248.  Description of  1878.  8th E d .  A Comparison o f t h e Neck and P r o t h o r a c i c  A c a d . N a t . S c i . P h i l a d e l p h i a , p . 353.  Ent.  N. Y.  33.  Comstock P u b l i s h i n g C b , I n c . ,  Ferris,  Ithaca,  of  32.  Comstock,  Cresson,  .230-281.  A Manual o f the Study  1899.  The C o m s t o c k P u b l i s h i n g C o . ,  J. H . , a n d J. G . N e e d h a m .  Comstock, Nat.  C a n . J. R e s . D , 26:  an  Ann0  18:: 22.  1937.  Recent Advances i n Entomology.  2nd E d .  J. & A .  London. A . D.  1906.  A Study o f t h e Wings o f t h e  a Superfamily of Hymenoptera.  P r o c . U . S.  N a t l . Mus.  Tenthredinidae,  29: 569-654.  41. Peck,  The M a l e G e n i t a l i a i n t h e H y m e n o p t e r a  1937.  0.  E s p e c i a l l y the F a m i l y Ichneumonidae. Riegel,  G. T.  Rohwer, S. Wing.  Proc. Ent. Soc.  39:: 37-91.  Coll. 99 (14).  Coll.  J.'R.  64(10):  Hymenoptera.  99. Hymenoptera.  Proc. U.  S.  16 P i s . Insect Morphology.  McGraw-Hill  Smiths.  The S k e l e t o - M u s c u l a r M e c h a n i s m o f t h e H o n e y  Bee.  103(2).  1937.  Society,  A Glossary  of Entomology.  B r o o k l y n Entomo-  Brooklyn, N. Y. 1944.  Ichneumonidae  Walker, E . M .  3 Pis.  33 P i s .  1942.  H . K. J r .  Nearctic  20-76.  Hymenopterous  The M a l e G e n i t a l i a o f H y m e n o p t e r a .  1941.  Snodgrass, R. E .  Townes,  Ann. Ent.  N. Y.  Snodgrass, R. E .  Smiths. Misc.  18 (1):  Principles of  1935.  Book C o . I n c . ,  logical  221-274.  (Hymenoptera).  Horismology of the  1916.  The T h o r a x o f t h e  19H.  Snodgrass, R. E .  Torre^-Bueno,  Wash.  29:  Am.  R. E .  N a t l . Mus.  D , 15:  The A n c e s t r y a n d W i n g V e n a t i o n o f t h e  1936.  Ann. E n t . Soc. Snodgrass,  Res.  439-449.  A . , and A . B . Gahan.  Ross, H . H .  Misc.  The W i n g s o f B r a c o n i d a e  1948.  S o c . Am. 41:  Can. J .  (Insecta),  A Catalogue and R e c l a s s i f i c a t i o n (Hymenoptera).  of  Mem. A m . E n t . S o c .  the 11.  Prognathism and Hypognathism i n I n s e c t s .  1932.  Can.  Ent.  223-229.  Wigglesworth, V . B.  1939.  & Co. L t d . , London.  The P r i n c i p l e s o f  Insect Physiology.  Methuen  

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