Stimuli eliciting sexual pursuit in the digger wasp Bembex rostrata (L.) males (hymenoptera, sphegidae). I. The choice of an adequate method for the ethometry survey

Abstract

Ethometry (i.e., quantitative, numerical analysis) of approach of the insect to objects moved in the air with a fishing rod and their pursuit proved a successful field method for objective evaluation of the valence of an object's features for Bembex rostrata males tested during their "sun dance". The maximum distance from which the insect reacts with a leap toward the object being a parameter of its approach, is directly proportional to the conspicuity of the object. The time of "behavioural interest" of the insect in the object, a measure of pursuit, reflects the persistence of the insect's attraction to the object, which is directly related to its valence. It is suggested that the sun dance is mainly a comfort behaviour, when the male is at the same time highly sensitive to sexual stimuli. Approach to a flying object is not a simple reflex-like tactic behaviour but a motivated one. Probably it is partly an exploratory, and to some extent a sexual behaviour, whereas pursuit is to a considerable extent dependent on a sexual mood. Hence, both can be regarded as the steps of a sexual appetitive behaviour. Experiments revealed a considerable variability of reactions among individual B. rostrata males. Differences between years of experimenting exert significant influence on results, too.