Energy Reserves and Mating Success in Males of the Yellow Dung Fly, Scathophaga stercoraria

Abstract

1. Carbohydrate (glycogen, fructose and other sugars) and lipid contents of mate-searching males were analysed in the Yellow Dung Fly, Scathophaga stercoraria. Males were classified into three relative age classes according to wing wear. 2. Fructose content increased towards the afternoon suggesting that males feed on nectar during the daytime. 3. Both carbohydrate and lipid contents were positively related with male body size. When controlled for body size, males that caught a female contained more glycogen and fructose as compared to males that failed to do so within each age class. 4. Among males copulating with a female, males on cow pats differed significantly from those in the surrounding grass by having more glycogen, sugars and lipids. 5. The results suggest that males successful in mate searching are in a better energetic condition than unsuccessful males. Energy acquisition can be an important component of mating success in species where mate searching involves frequent flying.