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Species Efferia aestuans - [Nerax] aestuans

Robber Fly killing Damselfly - Efferia aestuans Robber Fly w/prey - Efferia aestuans - female Robber Fly 7-22-09 - Efferia aestuans robber fly - Efferia aestuans - male wasp feeding? - Efferia aestuans Cooperative Robber Fly - Efferia aestuans robber fly - Efferia aestuans Robber fly - Efferia aestuans
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 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).
Size
body length: 18 mm (male); 23 mm (female)
Identification
tibiae partially reddish, mystax (moustache) black, ventral surface of abdomen has long white hairs; female has long blade-like ovipositor
Range
Ontario and New Hampshire south to Florida, west to Wyoming and New Mexico
Remarks
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.