Robber Fly: Stenopogon Species

Robber Fly, Stenopogon species, Imperial Beach. I had a tough time figuring out which genus this little robber fly is in. I started off with the genus Omnatius which came up in my online searches for Robber flies but are largely limited to the East Coast. However, Jim Berrian at the San Diego Natural History Museum kindly suggested the genus Machimus and Stenopogon, both of which have been found in Southern California. After some comparing of antennae, carapace shape and foot structure I'm convinced it's a Stenopogon (not that our Gentle readers really care but it gives me a feeling on completeness, go figure).

They are apparently called Robber flies because these capable little carnivorous flies catch other bugs on the wing. Think of it like robbers catching a coach on the trail. They bear some superficial resemblance to dragonflies which also snag food on the fly, no pun intended (Ar, Ar...). How they eat that food is, however, quite different. Robber flies inject saliva and disolve their food (think of it as liquid food on the go). Dragonflies use large mandibles to chew and ingest their food. In fact, Dragonflies are in the order Odonata, meaning "toothed jaws."

Side note: apparently, there was a large sewage spill off of Tijuana Beach (Playa de Tijuana) last week, leaving the Tijuana Estuary Beach largely deserted and peaceful. There were a few people strolling down the long strand of white sand. Otherwise, there were just the passing flocks of pelicans and the occasional shore bird. Overall, it was nice and quiet, with a gentle (and smell-free), cooling ocean breeze, which is a real find on a hot, Summer day during the Labor Day Weekend. While we stayed out of the water, there was no obvious evidence that a spill had happened just a week prior. There was just empty beach out to the horizon.