Female Mating Behaviour and Multiple Matings in the Fly, Dryomyza Anilis

Abstract

Multiple matings by females of the fly, Dryomyza anilis, were studied at small carcasses where they arrived to lay their eggs. Males of the species are territorial and fight over females and their oviposition sites. Arriving females were quickly captured by males and male fights over females as well as take-overs were common. The average number of matings per female was 2.8 and the average time a female spent at the carcass was 1 h 49 min (from arrival to the end of oviposition). The total mating time was almost twice as long in females which mated over five times than in females which had only one mating. The increase in mating time with increasing number of mating was totally due to the increase in time spent in copulation bouts (the species copulates and oviposits in several bouts). In attacks by lone males resulting in the separation of a pair, the attacker continued with the female in only one half of the cases (take-overs). In the other half a third male captured the female after she had escaped from the struggling males. In successful take-overs the new mate was usually larger than the earlier mate whereas in the other cases the new mate was almost always smaller than the earlier mate. Female resistance during matings was common and the various conflict behaviours are described. Female resistance became stronger in consecutive matings and within the same mating females resisted earlier in the second copulation bout than in the first one. In addition, larger females resisted more per mating, spent less time in copulation bouts per mating and had fewer matings than small females. Some possible costs and benefits of multiple matings were studied. Owing to male mating behaviour, where females are taken away from the carcass, females may loose feeding opportunities which can reduce their egg production. Male mating behaviour also delays female oviposition which can put the larvae in a worse position in food competition with other earlier larvae. Females arriving at carcasses to lay eggs face a situation where they can benefit from male guarding during oviposition but male fighting and take-overs can result in a long chain of matings which is disadvantageous for them.