Bombylius major -- "...the hairy and handsome harbingers of spring." --Frank R. Cole
I've finally gotten a half-way decent photo of a Bombylius bee fly; this is probably B. major, a common and widespread (as in much of the Northern Hemisphere) species.
As adults, Bombylius feed on nectar by hovering over early spring flowers. The larvae are parasites in the nests of solitary bees, feeding on the food stores and larvae of the hosts. Thus, the adults must find the burrows of solitary bees before they are sealed up, and lay their eggs in them. It would seem most straightforward if Ms. Bombylius just went directly into the nest burrow, but I suppose that the hosts have all sorts of defenses against such an intrusion. Instead, the female Bombylius hovers over the hole and flicks her eggs inside. Wow. I've watched them searching for burrows, investigating what I presume must be likely-looking (from a bee fly's point of view) holes, the forceful breeze from their wings tossing and scattering grains of soil as if a tiny tornado was attacking a square-inch patch of ground. But so far, I've not seen the old ovum toss. I'll keep looking; I'm a bit taken by these insects. Stylurus says they look like little plush toys. It's a compliment not paid to many flies, I'm sure.
Here's a nice article on bee flies, featured as "Bug of the Month", where I found the Frank Cole quote above.
