ENERGY RESERVES AND MATING SUCCESS IN MALES OF THE YELLOW DUNG FLY, SCATHOPHAGA-STERCORARIA

1. Carbohydrate (glycogen, fructose and other sugars) and lipid conten ts of mate-searching males were analysed in the Yellow Dung Fly, Scath ophaga stercoraria, Males were classified into three relative age clas ses 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 femal e, males on cow pats differed significantly from those in the surround ing grass by having more glycogen, sugars and lipids. 5. The results s uggest that males successful in mate searching are in a better energet ic condition than unsuccessful males. Energy acquisition can be an imp ortant component of mating success in species where mate searching inv olves frequent flying,