Male antler flies (Protopiophila litigata; Diptera : Piophilidae) are moreselective than females in mate choice

We investigated mate choice in the antler fly (Protopiophila litigata Bondu riansky), which forms mating aggregations and oviposits exclusively on disc arded cervid antlers, by pairing males with nongravid females and by collec ting copulating pairs on antlers. Because females probably receive larger e jaculates (which they partly ingest after mating) and more effective protec tion (mate guarding) from large males than from small ones, we expected fem ales to prefer large males as mates. Because males experience high mating c osts and often encounter females lacking mature eggs, we expected males to reject some females. Moreover, because relative abdomen width (fatness) pre dicts the number of mature eggs (egg load) of a female better than her body size does, we expected males to evaluate female quality by assessing femal e fatness. Of the 54 male-female pairings, 7 (13%) resulted in copulation, the female rejected the male in 6 (11%), and the male rejected the female i n 41 (76%). We found no significant differences between individuals that ma ted and those that did not. However, females disproportionately rejected ma les smaller than themselves. Males exhibited a preference (quantified as du ration of abdominal tapping bouts) for fat females as mates. Small males ap peared to be less choosy than large males. Because males rejected potential mates more frequently than females (apparently) did, males may have been c hoosier than females. Coupled pairs collected on antlers exhibited positive assortment by body size and positive correlation of male body size with fe male egg load. These mate-choice and mating-assortment patterns may occur i n many dipteran species, where copulation is costly for both sexes, females often lack mature eggs, and mating is initiated in dense aggregations of a ggressive males.