Saturday, August 29, 2009
So I was standing in the driveway next to the cactus collection about an hour before sunset on a day last month when I heard an unusual buzz go by. I'm not saying I can id any bug by its buzz, but when you've been observing insects awhile you get tuned into the particular sounds each species makes as it flies. So I recognized that this one was different: a loud-ish, dry/clattery sound of a lower than average pitch. The maker of the sound became apparent as it landed on a pod of the nearby feathery cassia (Senna artemisioides): a large (body length about 3/4", wingspan a bit more) fly with highly decorated wings and unusual (kinda scary-looking) eyes.
This is a bee fly (family bombyliidae) in genus Xenox. I'm semi-educated-guessing the species as X. habrosus based on comparison of the wing markings and appearance of the thorax in photos here. (Thanks guys at NatHist of OC). The generic name xenox comes from the Greek for stranger or alien, and those weird bug-eyes must have inspired the name. This fly has been a stranger to my property, this being the first time I've seen (or heard) it. This particular individual hung out on the cassia pod until after dark . . . maybe spent the night there, but was gone by the next day.
These bee flies parasitize solitary bees, such as the valley carpenter bees (xylocopa varipuncta) which are so plentiful around here. The female fly places her egg inside the entrance to the bee's nest where the fly larva feeds on the provender placed there for the bee larvae for part of its life cycle. Then the fly larva switches to feeding on the bee larva itself.
There has not been another sighting of this alien since July 24, but I've got my ears on for them.