Sunday, October 22, 2017
Bristle Butt the Fly
We had a frequent visit from Bristle Butt the fly last month. It was landing on my chair, clothes and arm, curious without intending harm. Finally it settled on my finger, begging to be photographed. I submitted pictures to Bugguide and came up with an identification of an Archytas spp. There are 15 species, all native of the Western Hemisphere but some species are now introduced into Hawaii.
The genus Archytas was named for Archytas, a classical Greek philosopher/mathematician. "He was reputed to have designed and built the first artificial, self-propelled flying device, a bird-shaped model propelled by a jet of what was probably steam, said to have actually flown some 200 meters."
Disclaimer: Most think it flew on a wire.
Archytas spp. are in the Tachinidiae family, the second largest family of Diptera (true flies). Diptera (two wings) have only one pair of apparent wings, the hind wings having been modified into stabilizers called halteres that control their balance. Their diagnostic features are described in Wikipedia but the most apparent one when sitting on my finger was its bristles all over the body, especially on the abdomen. They resemble an overweight housefly with a bad haircut.
In most species, their larvae are parasitoids, developing in a living host, careful to nibble only on nonvital organs to keep it alive until they pupate. Their host eventually dies. The majority of their host species are the larvae of plant eating insects such as grasshoppers, moths, true bugs and beetles. Many of these are juicy caterpillars, making them the gardener's friend. There are lots of hosts around so they are mainly a problem only if you are raising lepidoptera. The Bug Lady describes other Dipterian characteristics in more vivid detail. Our Archytas spp. above specializes on various moths, including Noctuidae or owlet moths, notorious for the armyworms and cutworms that attack our crops.
Once again, an insect that many people would swat just wants to make friends and is willing to help around the garden in trade for a little respect.