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Species Efferia aestuans - Eastern Hammertail

Friendly Robber - Efferia aestuans - male

Black Mustache Robber Fly - Dorsal - Efferia aestuans

Robber Fly? Neotamus sp.? - Efferia aestuans - male

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 (Hammertails)

No Taxon (Nerax group)

Species aestuans (Eastern Hammertail)

Synonyms and other taxonomic changes

Nerax aestuans

Explanation of Names

Efferia aestuans (Linnaeus 1763)

aestuans = 'scolding, boiling'

Eastern Hammertail: https://www.robberfliesoftheworld.com/NA_CommonNames.php

Size

male 19 mm, female 21 mm (1)

Identification

tibiae partially reddish, mystax black, ventral surface of abdomen has long white hairs; female has long blade-like ovipositor

Efferia kondratieffi Bullington and Lavinge (1984) is very similar. Robberfly.org says:

" E. aestuans are longer overall. Compared to E. aestuans, males have a shorter epandrium with a different shape to the tip of the epandrium. Females have a shorter ovipositor (3-4 mm) than E. aestuans (5-7 mm) giving it a more stout appearance, and a shoter arista (tip of antennae) (0.6-0.85 mm in E. kondratieffi vs. 0.7-1.2 mm in E. aestuans)."

Bullington and Lavigne (1984) also identify a possible additional species (Tex-coastalis) from Oklahoma and Texas. Current (2024) status of this taxon is unclear.

Reference: Bullington and Lavigne (1984). Description and Habitat of Efferia kondratieffi sp. nov. with Notes on Efferia aestuans (L.) (Diptera: Asilidae). Annals of the Entomological Society of America 77(4):404-413. DOI:10.1093/aesa/77.4.404 (Research Gate link)

Range

NH-ON-FL to ND-WY-UT-NM(2)

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 commonest species of Asilinae in the northeast (comment by Herschel Raney)

The type species of Efferia

Internet References

Species profile (3)

Robberfly.org

Works Cited

1.	Efferia Coquillett in America North of Mexico Wilcox, J. 1966. Proceedings of the California Academy of Sciences, 4th series., 34:85-234.

2.	Information on robber flies, compiled by F. Geller-Grimm

3.	Lavers N. (2007) The robber flies of Crowley's Ridge, Arkansas: An illustrated field guide

Contributed by john and jane balaban on 14 June, 2005 - 5:36pm
Additional contributions by cotinis, Robin McLeod, v belov, Chris Cohen
Last updated 5 June, 2024 - 8:58pm

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