Some Effects of Group Size on the Output of Beginning Nests of Mischocyttarus mexicanus (Hymenoptera: Vespidae)

Abstract

It is not known how pleometrosis (nest initiation in groups) and haplometrosis (nest initiation alone) are both maintained in the paper wasp Mischocyttarus mexicanus (Saussure). To answer this question, reliable measurements of the reproductive success of each tactic are needed. It is shown here that females that begin nests alone are more likely to raise a few daughters in rapid succession rather than many daughters at the same time. Females in small groups or alone also tend to have smaller first daughters than those females working in large groups. This difference in resource allocation between small and large groups causes measurements of per capita rates of production to correlate differently with group size depending on whether the number of cells, number of offspring, or weight of offspring added per day is measured. These data are consistent with the observation that haplometrotic females receive more predator and conspecific attacks than pleometrotic females, and thus produce their first daughters quickly to guard the nest. In addition the chronic mystery of a negative correlation between per capita productivity and group size in social insects is shown to be an expected outcome and not necessarily an indication that efficiency decreases with an increase in group size.