Body size and alternative mating tactics in the beewolf Philanthus zebratus (Hymenoptera; Sphecidae)

Abstract

A study of the mating behaviour of males of the beewolf Philanthus zebratus revealed that in one population males display variability in mating tactics and that this variability is related to male body size. There was a tendency for large males to patrol the airspace above the nesting area while smaller males were territorial adjacent to it. The mean sizes of the two groups of males were significantly different, although the size ranges of the two groups overlapped. Only 2.5% of the males were observed to undertake both mating tactics, at different times. Observations are presented on daily and seasonal activity patterns and on the relative location of nests, territories, and patrolling males. A second population, with lower nest density, was observed for several days, revealing only territorial males. It is suggested that the presence of patrolling males is related to the higher nest density of the one population. The fact that patrolling males tend to be relatively large is possibly related to flight energetics or simply to the ability of large males to seize females, which are usually larger than males, in mid-air.