Yesterday afternoon I took numerous photos of these wasps which were feeding on Jewelweed along a stream. Almost all of them were covered to some degree with this white substance which appeared to be attached to them. I watched them as they crawled inside of the flowers and the substance did not rub off. There were lots of bumble bees, too, in the area but only one bumble bee was covered with this white substance. One honey bee also had white on it. Is this a fungus? The wasps did not seem to be affected at all by the substance and they were quite active.

I received this reply from PJ Liesch at the UW-Madison Dept. Entomology Insect Diagnostic Lab

"This one has me scratching my head at the moment. The material does visually resemble fungal material, although if it were an entomopathogenic fungus I wouldn't expect to see the insects out foraging. In my experience, if an insect is infected with a fungus, it's usually long dead by the time fungal hyphae become readily visible on the surface of the exoskeleton."

"I also wonder if the whitish fuzz might be materials picked up somewhere: plant trichomes or other materials, waxy materials (if they had collected honeydew near wooly aphids), etc... This one might remain a mystery for the time being!"