One of several hypotheses proposed to explain polyandry in eusocial insects is the parasite–pathogen hypothesis (PPH), in which a colony of workers with multiple patrilines due to queen polyandry is less likely to fall victim to a parasite or pathogen threat because of genetic variability of the colony’s workforce. We challenged colonies with different strains of an entomopathogenic fungus to determine pathogen virulence and worker survival. We found that workers from different patrilines differed in their survival following the pathogen challenge, supporting the hypothesis that a major benefit of multiple mating by queen wasps is in disease resistance for the benefit of the colony.

We infected isolated workers with the entomopathogenic fungus Beauveria bassiana and quantified their survival in the laboratory. We used five fungal strains (A–E) of B. bassiana for experiment 1, and then selected the two most lethal strains (A and C) for experiment 2. We used nine microsatellite markers to determine patriline membership, we analyzed microsatellite genotypes using the software Colony v2.0.6.5 (Wang 2004).