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Species Asilus sericeus

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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 Asilus
Species sericeus (Asilus sericeus)
Synonyms and other taxonomic changes
Say 1823 Asilus sericeus; Walker, 1849 Asilus herminius
Explanation of Names
Asilus sericeus Say 1823
Greek 'silky'
20-28 mm(1)
Head: Covered with golden pile, including behind the eyes. Row of brownish bristles across back of head. Mustache (mystax) has a thin layer of very long brownish-yellow bristles.
Antenna: Base segments more brownish-yellow. Segment 3 long, black, with bristle at tip.
Thorax: Brownish-yellowish pile with wide dark stripe down center. Thorax sides more reddish-brown, no pile.
Wings: Light reddish-brown, cells along inner margin and wing tip dusky; veins wide, light reddish-brown. Halteres yellow.
Legs: Thighs (femora) reddish-brown, may have dark streak. Shins (tibiae) and feet pale yellowish. Last few segments of feet darker. Toes yellow. Only a few thin, short spines on legs.
Abdomen: Long, slightly tapering. Variable color, depending on light conditions. First 4 segments dark brown, lower margin golden. Last few segments lighter brown, barely marked on lower margin. Male tip spoon-shaped. Female tip long and sharply pointed, reddish-brown.
e. NA (ME-FL to ON-ND-TX)(2)
Wet meadows, especially with fern; fields, etc. with flowers.
Jun-Aug(3)(4); one report November in Michigan.
Often preys on nectar-seeking insects such as butterflies, catching them in mid-air. Not known to feed on bees and wasps like other robber flies. Larvae feed on smaller, ground-dwelling insects. Mistakenly reported feeding on roots of rhubarb.
Life Cycle
Larvae 18 – 20 mm long; grub-like, white, tinted yellowish. Head is brown with 2 small hooks. Lives about 16 cm underground. Pupates in late May, moving to surface to emerge by mid June.
Holotype as Asilus sericeus by Say, 1823. Type Locality: Pennsylvania. Type lost.

Holotype as Asilus herminius female by Walker, 1849. Type Locality: Massachusetts. In the British Museum of Natural History, London, England.
See Also
Similar Species: A larger robber fly than Machimus species, but similar. Appearance is more yellowish in color, including legs. Legs have very few bristles, unlike Machimus.
Print References
Journal of the Academy of Natural Sciences of Philadelphia, 1823-24, Vol. 3 by Say, pg. 48.
List of the Specimens of Dipterous Insects in the Collection of the British Museum, 1849, Pt. 2 by Walker, pg. 410.
Guide to the Study of Insects, 1869 by Packard, pg. 396.
The Kansas University Quarterly, 1893, Vol. 2 by Williston, pp. 68-69.
Annals of the Entomological Society of America, 1909, Vol. 2 by Hine, pg. 136.
The Great Lakes Entomologist, 1975, Vol. 8 #2 by Baker & Fischer, pg. 73.
Works Cited
1.American Insects: A Handbook of the Insects of America North of Mexico
Ross H. Arnett. 2000. CRC Press.
2.Information on robber flies, compiled by F. Geller-Grimm
3.Insects of North Carolina
C.S. Brimley. 1938. North Carolina Department of Agriculture.
4.Kaufman Field Guide to Insects of North America
Eric Eaton, Kenn Kaufman. 2006. Houghton Mifflin.