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Family Pyrgotidae

Pyrgotid Fly  - Boreothrinax maculipennis Sciomyzidae? - Sphecomyiella valida Mottled-winged fly - Sphecomyiella valida Pyrgotid Fly? - Pyrgota undata Pyrgotid Fly - Boreothrinax maculipennis Sphecomyiella nelsoni? - Sphecomyiella - female Pyrgotidae, frontal-lateral - Sphecomyiella valida Fly
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Diptera (Flies)
No Taxon ("Acalyptratae")
Superfamily Tephritoidea
Family Pyrgotidae
Synonyms and other taxonomic changes
reviewed in(1)
Explanation of Names
Pyrgotidae Loew 1868
9 spp. in 5 genera in our area(2), ~350 spp. in ~60 genera total(3)
NA species have brown patterning on the wings and lack ocelli

Head-patterning comparison between genera Sphecomyiella and Boreothrinax:

In general, the head pattern of Sphecomyiella will be darker in the top-down view, stretching to the top of the head, while in Boreothrinax it is lighter and only reaches the middle of the frons (though in Boreothrinax maculipennis there is commonly some lighter streaks that can reach close to the top of the head.
For the posterior pattern of the head, Sphecomyiella is shaped in a triangle, with the center always filled and the corners of this triangle sometimes constricting to form more of a stellate pattern. In Boreothrinax, there are two relatively thick dark bands (sometimes parallel, sometimes divergent) connected at the bottom by a darker area, which always has an "m" shaped light mark cut out.
Life Cycle
Larvae are internal parasites of adult Scarab beetles. Only a single larva develops in each beetle--killing the beetle within two weeks. The female fly is reported to insert eggs into the abdomen of the beetle while both are in flight, generally at night.(4)
Usually found around lights at night. Very rarely seen during the day.
Works Cited
1.Synopsis of the North American Pyrgotidae (Diptera)
Steyskal G.C. 1978. Proc. ent. Soc. Wash. 80: 149-155.
2.American Insects: A Handbook of the Insects of America North of Mexico
Ross H. Arnett. 2000. CRC Press.
3.Order Diptera Linnaeus, 1758. In: Zhang Z.-Q. (ed.) Animal biodiversity: An outline of higher-level classification...
Pape T., Blagoderov V., Mostovski M.B. 2011. Zootaxa 3148: 222–229.
4.Manual of Nearctic Diptera Volume 2
Varies for each chapter; edited by J.F. McAlpine, B.V. Petersen, G.E. Shewell, H.J. Teskey, J.R. Vockeroth, D.M. Wood. 1987. Research Branch Agriculture Canada.