Glenn sacrificed a little blood in his effort to snap this photo. Most female horse flies or deer flies (family Tabanidae) feed on the blood of warm-blooded vertebrates, with slashing-sponging mouthparts making for a painful bite. Similar to a mosquito, a blood meal is required for the development of eggs. Males, on the other hand, solely visit flowers and do not bite.
Deer flies in the genus Chrysops are on average smaller than horse flies and usually have dazzling, spotted eyes and blotched wings. Both sexes have large eyes, but the eyes meet on top of the head on males and are separated on females (a female is pictured here). This fly is on the wing from late June to early August from southern British Columbia to California and Wyoming. Larvae live in wetland soils, stream edges, seeps, and associated mosses, where they prey on invertebrates.
Photo by: Glenn Marangelo on 7/17/21 near Philipsburg, MT