Mate recognition in the two-spot ladybird beetle, Adalia bipunctata: role of chemical and behavioural cues

On encountering a mature female, a male of the two-spot ladybird, Adalia bi punctata (L.), first palpated her elytra with his maxillary palps, then mou nted her, extruded his penis and mated. Copulation never occurred between a ctive males but males copulated with dummies bearing male elytra as frequen tly as with dummies with female elytra of their own species. Similarly, mal es attempted mating with immobilised conspecifics of both sexes. However el ytra washed in chloroform failed to stimulate mating. Analysis of the chlor oform extracts of the elytra revealed that male and female ladybirds are co ated by the same blend of hydrocarbons among which 9- and 7-methyl tricosan e are dominant. Our results are consistent with a role of these cuticulars hydrocarbons in species recognition and show that behaviour, in particular movement, is necessary for discrimination between males and females. (C) 19 98 Elsevier Science Ltd. All rights reserved.