The sexual behavior of the robber-fly Mallophora ruficauda Wied. (Asilidae, Asilinae) in normal and experimental conditions

Abstract

Field observations have revealed that males of the robber-fly Mallophora ruficauda Wied. perform the following sequence of motor actions during courtship: (1) hovering; (2) rhythmic flicking of the third pair of legs; and (3) copulation attempts. Contrasting with the activity exhibited by males, females of Mallophora remain practically motionless during the sexual display. We have only detected vibrations of the wings triggered by the contact of the third pair of legs of dancing males. (These different motor actions have been grouped in three sequential phases of courtship termed 1, 2 and 3; Fig. 2.) Copulation occurs after thirty to forty minutes of courtship. Rustic dummies showing the main color pattern of the species are able to release the different phases of the sexual display. In these circumstances, however, copulation attempts occur very soon, a few seconds after detection of the potential mate. It is important to note that courtship is also elicited by atypical dummies not showing the color patterns characteristics of this species (BDs, IDs). Conversely, RDs and YDs are ineffective for triggering courtship. The experiments performed with dummies of different sizes demonstrated that phase 3 of courtship only occurs with normal or oversized dummies. It was also found that dummies pinned on a vertical twig, with their longest axis oriented parallel with respect to the ground, rarely elicit complete sexual display. Concerning the biological significance of courtship in this species, our findings suggest that the sexual display of the male inhibits the fleeing tendency of the female (FaM type of courtship according to Morris [10]).