July 11, 2010
Sure thought this was a smallish wasp, but finally found out it’s a thick-headed fly. Thought you might like a picture.
As we were working on your post, we realized we needed to create a new category for Thick Headed Flies. We will need to search through our archives to see if we have any older postings of Thick Headed Flies in the family Conopidae, but this might be a first for our website. We believe your specimen may be in the genus Physocephala, which BugGuide describes as “adults feed on flower nectar Females usually oviposit on hosts (mostly bumble bees and wasps) during flight. Larvae become internal parasitoids (usually kill the host).“ There is additional clarification of the life cycle on BugGuide: “P. tibialis has been reported to parasitize workers of the bumble bee Bombus bimaculatus. Adults apparently alight and inject an egg into the abdomen of their host while in flight. A study in Alberta showed that bumble bees parasitized by P. texana had the same lifespan as unparasitized individuals (Otterstatter et al, 2002; …).“
Ed. Note: A previous posting of a Thick Headed Fly from 2009 was added to the new category.