MALE DISTRIBUTION AND MATE SEARCHING IN THE YELLOW DUNG FLY SCATHOPHAGA-STERCORARIA - COMPARISON BETWEEN PAIRED AND UNPAIRED MALES

Movements by individual males were examined in the yellow dung fly, Sc athophaga stercoraria. Males were observed from their arrival until th ey found a female (paired males) or departed (unpaired males). The foc al variables were the male mating status, body size and the number of males and females at the site. Paired males, independent of size, spen t more time in the best mate-searching area (pat and the first up-wind zone) than unpaired males. Paired males in all size classes moved aro und and attacked other males more often than unpaired males. Among pai red males, males that caught a single female and those that took over a female from another male were very similar in their mate-searching b ehaviour. The total time spent searching at the pat was positively rel ated to its resource value as indicated by the number of pairs. Time s pent in the best mate-searching area was negatively related with male numbers. The causes of differences in movements and aggression between paired and unpaired males are discussed. The male distribution around cow pars can be understood only if the differences in movement patter ns by paired and unpaired males are taken into account.