Factors mediating copulatory behavior and close-range mate recognition in the male gypsy moth, Lymantria dispar (L.)

Physical models incorporating various structural features of female gypsy moths, Lymantria dispar, were used to identify the specific factors that evoke conspecific male copulatory behavior and play a part in mate recognition. Models invested with virgin female wings or body scales elicited male copulatory responses comparable to those evoked by virgin females. The presence and diameter of models also influenced male copulatory reactions. Exposure to sex pheromone was necessary to prime copulatory behaviors but, by itself, was not sufficient to release these reactions. Males expressed copulatory behaviors most faithfully when the pheromone was supplemented with female abdominal scales applied to cylindrical models either comparable in size or larger than a female. To establish the nature of the cues that prompted copulatory reactions and the sensory basis of these responses, female scales were chemically and structurally altered and male sensory structures were selectively ablated. Solvent, acid, or base extraction of female abdominal scales did not diminish the copulatory response whereas pulverization of the scales eliminated it. Models impregnated with solvent extracts of female abdominal scales elicited copulatory behavior from a higher proportion of males than did controls without extracts, although the mean time spent attempting to copulate did not differ significantly. Males whose compound eyes, tympana, tarsal chemoreceptors, labial palps, or genitalia were ablated displayed fundamentally the same copulatory behaviors as their sham-operated counterparts whereas antennectomy eliminated mating behaviors. Taken together, these findings indicate that tactile cues associated with females serve as primary releasers of copulatory behavior for sex pheromone stimulated males and that chemicals affiliated with female body scales appear to play a relatively minor role in this process.