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Species Physocephala furcillata

Diptera - Physocephala furcillata Conopidae - Thick-headed Flies  Physocephala furcillata - Physocephala furcillata Physocephala cf furcilliata - Physocephala furcillata - female Thick-headed Fly (Physocephala) - Physocephala furcillata Unidentified Fly - Physocephala furcillata Physocephala? - Physocephala furcillata - male Physocephala? - Physocephala furcillata - male Physocephala furcillata? - Physocephala furcillata - male
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Diptera (Flies)
No Taxon ("Acalyptratae")
Superfamily Sciomyzoidea
Family Conopidae (Thick-headed Flies)
Subfamily Conopinae
Genus Physocephala
Species furcillata (Physocephala furcillata)
Synonyms and other taxonomic changes
Synonymy below from (1), hyperlinks go to original descriptions:
  Conops furcillatus Williston, 1882, Trans. Conn. Acad. Arts & Sci., 4:336
  Physocephala sororcula Williston, 1892, Biol. Cent.- Amer., Diptera, 3:83
  Physocephala lucida Van Duzee, 1931, Can. Ent., 63:284
Explanation of Names
The specific epithet furcillata is Latin for "forked".
Perhaps this refers to the black facial markings at and just below the antennae? Note that the original description in Williston(1882) includes the sentence (green italics added): "Vertical callosity black, bordered in front with opaque black, extending as a medial stripe to the antennae and there divaricating and passing as a black line upon each side of the face". But note that many Physocephala species have this trait — it is not unique to P. furcillata.
10-12 mm
Dark species: blackish...but often with subtle bronze or reddish-brown overtones. Discal cell hyaline, costal cell hyaline to pale brown. White spots on shoulder pads small to absent. No white marks on thorax sides. Cheeks black, facial grooves pale.
Head: Vertex (top of head) black. Frons marked in the shape of a "T", with its lower medial portion extending below the base of the antenna as two black lines along each side of the facial ridge (= an inverted-"V" between the base of the antenna and the mouthparts). Face mostly white to yellowish. Facial grooves (within ridge) pale yellow to white. Cheeks black. Back of head (occiput) black, dusted white pollinose. No white stripe on hind eye margin. Proboscis black.
Antenna: Black. 1st segment noticeably shorter than in other species. Segment 1 and 3 reddish-black on underside.
Thorax: Black. Humeral spots ("shoulder pads") inset toward center of thorax, yellowish/white pollinose, small and short, may be faint or entirely absent. Scutum (large central portion of dorsum of thorax) black, may have some reddish around outside edges. Scutellum (thinly-oval hind portion of dorsum of thorax) usually black, rarely with indistinct brownish-yellow bar. Pleura (sides of thorax) with some reddish color or thin reddish lines, no white marks.
Wings: Anterior half of wings dark. The long, sliver-like costal cell (along forward edge of wing) is lighter brown to pale. Hyaline spot on lower edge of R5 (longer than in marginata). Posterior half of wings hyaline, including the discal cell.
Legs: Mostly reddish to reddish-brown. Front and hind coxae dark with silvery-white spots. Thighs (femora) reddish-brown, sometimes darker toward base, tips light. Shins (tibiae) with basal half yellowish, rest reddish-brown. Feet (tarsi) reddish, except terminal segments which are darker (typically blackish).
Abdomen: Black. Segment 2 (petiole) lower half on the sides, and sometimes on the base of segment 3 may be light reddish-brown. All segments have transverse yellowish-white stripes at segment ends, segment 2 stripe wider. Top of segments 4 to 6 with light yellowish-white dust. Female pad (theca) on underside of segment 5 medium-sized.
Alberta to Nova Scotia, south to Wisconsin and Pennsylvania. Also Mexico, and possibly California. (1)
Flight Time: July to August
Adults nectar at flowers. Larva are thought to be parasitoids on bees and wasps.
Reported parasitizing bumble bees...see remarks and comment thread here
Original 1882 description by Williston here.
Holotype male from Van Duzee as Physocephala lucida in California Academy of Sciences #04449 - no photo – also one from Gull Lake, Ontario.
Three cotypes male and female, Jefferson, New Hampshire, ‘White Mts.” Museum of Comparative Zoology, Cambridge, Massachusetts (Snow Entomological Collections, Lawrence, Kans.).
Camras collection of fifty-seven Physocephala furcillata specimens donated to the Field Museum, Chicago, Ill.
See Also
P. tibialis can look very similar, but has:
Discal cell of wing dark; facial grooves black; 1st antennal segment longer than in furcillata. Also, the body is usually more pure black, with less of a bronzy or reddish cast (though the sutures between sclerites are often quite red).

P. marginata can also look very similar, but has:
Discal cell hyaline as in furcillata, but the sliver-like, leading-edge costal cell is dark; the humeral spots ("shoulder pads") conspicuously larger; cheeks brown/black with pale-yellowish central area; facial grooves dark; first antennal segment longer; yellowish-white mark on side of thorax below wing base, narrowed above (sometimes subtle); and a partial white stripe on the hind eye margin.
Print References
Williston, S. W. (1882). North American Conops. Trans. Conn. Acad. Arts & Sci., 4:336 (Orig. descrip. as Conops furcillatus)
Williston, S. W. (1885). North American Conopidae. Trans. Conn. Acad. Arts & Sci., 6:391 (Key w/ P. furcillata)
Van Duzee, M. C. (1931). A new species of Physocephala from Ontario, Canada. Can. Ent., Vol. 63, #12, pg. 284 (Descrip. as P. lucida)
Parsons C.T. (1948) A classification of North American Conopidae. Ann. Ent. Soc. Am. 41: 223-246 (Full text)
Camras, S. and P. D. Hurd, Jr (1957). The Conopid Flies of California (Diptera)(2), Bull. Cal. Insect Survey Vol 6, No.2 (Full Text)
Camras, S. (1957). A review of the New World Physocephala (Diptera: Conopidae). Ann. Ent. Soc. Am. 50:213-218.
Camras, Sidney (1996). New information on the New World Physocephala (Diptera: Conopidae), Entomological News, 107(2): 104-112 (Full Text)
Mei, M., Gibson, J.F., and Skevington, J.H. (2008). Observations on Hilltopping in Thick-Headed Flies (Diptera: Conopidae), J. Insect Sci., Vol.10, No. 27, pp 1-15 (HTML or PDF)
Internet References
Type images from the Harvard Museum of Comparative Zoology. [Note: The 6th image on that page current shows a wing of Physoconops brachyrhynchus...only the first 5 images show Physocephala furcillata.]
Works Cited
1.A Catalog of the Diptera of America North of Mexico
Alan Stone, et al. 1965. United States Department of Agriculture.
2.The Conopid Flies of California
Sidney Camras and Paul D. Hurd, Jr. 1957. University of California Press.