Cerotainia

Very tiny twig-perchers with long antennae. Atomosia also have long, stalked antennae.

The two species of Cerotainia are virtually identical, with C. albipilosa having much more white hair overall than C. macrocera. Eric Fisher noted it’s not certain they are separate species. Bugguide mentions that C. albipilosa has green eyes and C. macrocera has brown eyes, but I’m not sure that’s a consistent feature. These are both uncommon in Florida, though are much more common throughout their range in the eastern U.S. and Canada.

Cerotainia albipilosa

Face and top of head with grayish white hair. Black abdomen polished with either white pile (male) or black pile (female) dorsally. Femora entirely white-haired.

Size: 7-8 mm

Season: June – September over entire range

FL Season: March – September

FL Range: Throughout, though infrequently found.

Behavior: Forages from the tips of leaves, stems, and grass in sunlit areas around the margins of clearings and paths (Bromley, 1934; Scarbrough, 1978). Most foraging flights occur when prey fly near the Cerotainia‘s perch. Fourteen percent of flights were successful in capturing prey (Scarbrough, 1978).

Cerotainia macrocera

Face and top of head with brownish hair. Black abdomen semi-polished with more erect, largely black pile on the mesonotum (top of thorax). Femora with white hairs laterally and ventrally, but brown hair dorsally, but this can be difficult to see.

Size: 5-9 mm

Season: June – August throughout range

FL Season: All year? (Jan, May, June, Sept, Nov records in FSCA)

FL Range: Throughout, though infrequently found.

Behavior: Perches on tips of leaves and twigs

Habitat: McCravy and Baxa (2011) found this species was associated with previously burned prairies, but Scarbrough (1974) found this species to be common at various study sites in Maryland.

References:

Baker, N. T., & Fischer, R. L. (1975). A taxonomic and ecological study of the Asilidae of Michigan. The Great Lakes Entomologist, 8(2), 1.

Bromley, S. W. (1950). Florida Asilidae (Diptera) with description of one new species. Annals of the Entomological Society of America, 43(2), 227-239.

Curran, C. H. (1930): New American Asilidae (Diptera). American Museum Novitates 425: 21 pp.

McCravy, K. W., & Baxa, K. A. (2011). Diversity, seasonal activity and habitat associations of robber flies (Diptera: Asilidae) in West-Central Illinois. The American Midland Naturalist, 85-97.

Scarbbough, A. G. (1974). Faunistic study of Asilidae (Diptera) at three locatins in northern Baltimore County, Maryland: incidence, relative abundance and seasonal distribution. Proceedings of the Entomological Society of Washington.

Scarbrough, A. G. (1977). Ethology of Cerotainia albipilosa Curran (Asilidae: Diptera) in Maryland: diurnal activity rhythm and seasonal distribution.

Scarbrough, A. G. (1978). Ethology of Cerotainia albipilosa Curran (Diptera: Asilidae) in Maryland: predatory behavior.