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Studies of some aspects of behaviour in the ambrosia beetle, Trypodendron lineatum (Olivier) Francia, Faustino C.

Abstract

Tim factors and mechanisms which consistently deliver newly overwintered adults of the ambrosia beetle Trypodendron lineatum (Olivier) to specific host trees under specific conditions have been considered. Studies and analyses of the behavioural patterns of the beetle in respect to light, host tree factors, and factors of the environment were made in recognition of the fact that preliminary research results demonstrated the predominant role that reactions to light played!, in the behaviour of the beetle. The results of the studies showed that the beetles, before flight, were strongly phototacstic at temperatures in the range of 5° to 56°C. Positive photic response was inhibited in an increasing percentage of individuals at temperatures above 56°. At 38°C, positive response to light by the beetles ceased to exists. The non-flown beetles reacted quickly to angular deviations of alignment in respect to a light source and turned, with almost equal readiness toward the light regardless of its angle. The beetles' responses to light may be classified as follows: (1) not inhibited, the beetles immediately, move toward the source of light; (2) initially inhibited positive response; (3) inhibited positive response, the beetles may or may not initially inhibited but the general movement toward She light source is not direct; (4) completely inhibited response, the beetles move with no apparent response to light. The photopositive response was found to mask: the other potential capabilities of the non-flown beetles. Exclusion of the photic stimulus from flight-inexperienced beetles resulted in response to host odour in an odour field. Flight experience was found to modify partially the simple photic reaction of some individuals in the absence of host odour, but the majority of the beetles' responses remained unchanged. The behaviour of Trypodendron is not strictly stereotyped in the sense that it follows a definite pattern. While flight may be normal as a conditioning mechanism preparatory to alighting and host finding, response to an "attractive” odour source and subsequent boring behaviour may be exhibited, in the absence of previous flight experience, under certain conditions.

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