Sibling matings in a hunting wasp: adaptive inbreeding?

Upon emergence as adults, brothers of Euodynerus foraminatus compete among themselves for the microterritory around their natal nest. The winning male inseminates his sisters as they emerge several days later. Unlike most species that inbreed in a similar fashion, both sexes of this common wasp are strong fliers. The possibility is raised that siblings may be preferred as mates even when out-breeding is possible.