Presence of single-sex broods under local mate competition in Trypoxylon malaisei (Hymenoptera : Sphecidae): Adaptation or maladaptation?

In thr wasp Trypoxylon malaisei Gussakovskji mating occurs among siblings t hat have emerged fi om the same nest (local mate competition). Although loc al mate competition theories predict that mothers should produce the minimu m number of sons sufficient to inseminate all daughters in each nest, 30% o f nests that we examine contained only females, and 5% contained only males . We examined three nest properties (brood size, length of the unoccupied s pace and thickness of the outermost wall) to determine whether a nest was c omplete. All-female nests had smaller brood sizes, larger unoccupied spaces , and thinner outermost walls than mixed-sex nests. suggesting that all-fem ale nests were incomplete. All-male nests had brood sizes and unoccupied sp aces similar to those of all-female nests, although the thickness of the wa lls was inconsistent. We discuss problems arising from the inclusion of inc omplete broods in analyzing sex-ratio data.