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Genus Holcocephala

Fly Spp. - Holcocephala Pretty cute ... robber fly? - Holcocephala 9003727 Holcocephala - Holcocephala fly - Holcocephala calva Robber Fly - Holcocephala abdominalis - male - female Robber fly Holcocephala fusca? - Holcocephala Asilid - Holcocephala Small robber fly with big red eyes - Holcocephala
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Diptera (Flies)
No Taxon (Orthorrhapha)
Superfamily Asiloidea
Family Asilidae (Robber Flies)
Subfamily Trigonomiminae
Genus Holcocephala
Other Common Names
known commonly as "gnat ogres"
Explanation of Names
Holcocephala Say 1823
'grooved head'
Numbers
3 spp. in our area, ~40 total(1)
Size
under 10 mm
Identification
The very widely spaced eyes almost eliminates all other genera in the US
Species ID: here
"fusca is very similar to abdominalis (they are functionally a pair of cryptic species). H. fusca was described (in a very short, two sentence paragraph!) as being distinct from abdominalis by having a general darker color. It was soon treated as a synonym of abdominalis and essentially forgotten. Recent observations show that individuals with the darker 'fusca' coloration also have more slender antennae and legs (1st flagellomere of antenna of abdominalis distinctly broader in middle - with a spindle-shape; fusca has a more elongate, parallel-sided flagellomere 1; hind tibia & basitarsis of abdominalis about 35% broader than hind femur, while only about 15% broader in fusca); and a slightly different aedeagus shape. So, now I am tentatively treating them as distinct spp." --Eric Fisher
"Based on what I've seen working through the University of Michigan museum collection, I personally reserve abdominalis for the ones that are clearly yellow/light tan with a big ol' swollen hind tibia. I call dingy darker brown ones with slightly swollen tibiae fusca, and throw my hands up in the air for the ones in the middle. One of these days, I might get around to doing a bunch of dissections to see what's going on myself." --Tristan McKnight, 18.ix.2014
Range
primarily neotropical group, most diverse in S. America; in our area, e. US (west to WI-KS-TX) + ON; all three spp. are widespread(1)
Habitat
Grassy open areas near woods.
Season
Mid- to late summer
Food
Gnats and small flying prey