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Species Efferia aestuans - [Nerax] aestuans

wasp feeding? - Efferia aestuans Female Robber Fly gets prey - Efferia aestuans - female Efferia sp? - Robber Fly - Efferia aestuans - female Robber Fly Diptera Asilidae  - Efferia aestuans robber fly - Efferia aestuans Tabanid? - Efferia aestuans Robber Fly (with prey) - Efferia aestuans Female Efferia? - Efferia aestuans - female
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 Asilinae
Genus Efferia
No Taxon (Nerax group)
Species aestuans ([Nerax] aestuans)
Synonyms and other taxonomic changes
Efferia aestuans (Linnaeus, 1763)
Asilus aestuans (original combination)
Nerax aestuans is listed as a junior synonym at the USDA's The Diptera Site (dead link)
Explanation of Names
Likely from Latin aesta, "the summer heat" (1).
body length: 18 mm (male); 23 mm (female)
tibiae partially reddish, mystax (moustache) black, ventral surface of abdomen has long white hairs; female has long blade-like ovipositor
Ontario and New Hampshire south to Florida, west to Wyoming and New Mexico
The most likely robber fly to land on humans. (comment by Herschel Raney)
Sometimes fearless. The males are much less common and harder to approach. (comment by Herschel Raney)

The most common species of Asilinae in NE North America. (comment by Herschel Raney)

This is the type species of the genus Efferia.
See Also
Efferia albibarbis has white mystax, and female has shorter, more cone-like ovipositor
Internet References
classification and distribution (The Diptera Site, USDA--link dead)
Works Cited
1.Dictionary of Word Roots and Combining Forms
Donald J. Borror. 1960. Mayfield Publishing Company.