Identify a Wasp with a white face?
Location: Fairfield, Maine
August 3, 2010 7:45 pm
I found this on some goldenrod along with dozens of paper wasps. I seemed very camera shy or very busy, so I was only able to get this one picture. I looked through a lot of the potter wasps but did not find anything with the same markings and colors. Is this even a wasp at all?
This is not a wasp, but a fly that mimics a wasp. We suspect it is in the family Syrphidae, the members of which are called Flower Flies or Hover Flies. We are posting your photo as unidentified until we get an actual species or at least genus name. Perhaps our readers can assist us.
Correction thanks to Karl
August 4, 2010
This is a Thick-headed Fly [see BugGuide] (Conopidae), so named because of their relatively large heads. According to the Kaufman Field Guide to Insects of North America “They are mostly parasites of adult solitary bees, and sometimes wasps. The female fly assaults the host in midair, often forcing it to the ground and ramming an egg between the victim’s abdominal segments before releasing it.” I believe the genus is either Physocephala or Phyoconops, the difference apparently being that in Physocephala the hind femur is somewhat swollen at the base, whereas in Physoconops it is not. This feature is not always easy to distinguish but the femurs do appear slightly swollen in this individual. There are many very similar looking species but based on color patterns of the face, legs, wings and abdomen, I think this may be Physocephala marginata. Regards. Karl