Length: 14-15 mm
Look for these attractive flies from the end of May to the end of August.
Two of the records of Drees et al. (1980) were particularly interesting. One was of a larva collected in West Virginia "in a decaying beech tree well above the soil level." Previous collections of the larva of G. chrysocoma were from soil and leaf litter. Another West Virginia specimen had been the prey of a wasp, Vespa monticola, the first published record of a West Virginia Tabanid as prey.
As is often the case in this family, the males of G. chrysocoma are encountered less often than the females. The male shown here was found along the Black Fork of the Cheat River, in West Virginia.
John F. Burger (1995) gives the range of this species as "Ontario to Vermont and Connecticut, south to Arkansas and Georgia."
The species epithet means "Golden-haired." It was first described in 1875 by the great entomologist (and Russian diplomat in New York) Karl Osten-Sacken.
In 1932 in Arkansas, H.H. Schwardt found the mother lode of Goniops chrysocoma, a hillside where he found more than 400 larvae of this species. Schwardt found most on the surface of the soil under leaf litter. He also found a few under logs and rocks. Rearing larvae in jelly jars, Schwardt saw 52 through to adulthood. Though he examined many similar habitats nearby, he failed to find a single larva or pupa.
Schwardt noted that egg masses typically contained more than 300 eggs, and took seven days to hatch. He reported that nearly all the egg masses were laid on the underside of "hard maple" leaves, though he noted that other authors had reported other preferred leaves. After the eggs are laid,
"The female assumes a standing position over the eggs, so that her abdomen touches and forms a complete roof over them. She forces her tarsal claws entirely through the leaf, so that her position is very secure, and remains until death intervenes, or she is forcibly removed. A twig, bearing leaf, egg mass, and female fly can be removed from the tree, hauled several miles to the laboratory, photographed, and subjected to other unusual treatment without any apparent disturbance to the fly.... Usually the female fly dies and falls from the mass a few hours after the eggs hatch" (Schwardt, 1934).
Several authors including Schwardt have reported an apparent warning sound sometimes made by the female by vibrating the wings; the sound is like a fingernail being dragged along the teeth of a comb.
Schwardt mentioned a parasitic wasp he referred to as Telemonus goniops that attacks the eggs of Goniops chrysocoma. He stated that the damage to eggs was not bad early in the egg-laying season, but late in the season he collected blackened Goniops egg masses that soon yielded as many as 200 of the wasps, but no Goniops larva.
Schwardt found pupae in the same habitat as the larvae, without any protective cell. The pupal period lasted an average of 23 days. Emergence, in his Arkansas study area, came between May 12 and June 7.
Above: What may appear to be a piercing beak on this male Goniops chrysocoma is actually the pair of second palpal segments. Male horseflies don’t need a beak because they don't feed on blood.