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23 May 2012
length 4 mm

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head

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Dolichopus sp.

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Thank you, Stefan. What additional details are needed to have a chance of IDing it to species?

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Hello John! I suggest to ask a Canadian Dolichopodidae specialist.

Stefan

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Dolichopus aff. abruptus Aldrich, 1922

157.-Front tarsi with one or more segments compressed..................... 158.
Front tarsi plain............................................ 162.
158.-Hind femora ciliated below............................................ 159.
Hind femora without cilia............................................ 160.
159.-Front coxae yellow (Alaska) ........ ................ brayenemus Coquillett.
Front coxae wholly black (British Columbia) ..... ...... nigricoxa Van Duzee.
160.-Front tarsi blacK from the tip of first segment (Colorado) .... elegans Aldrich.
Front tarsi with at least first two segments yellow....................... 161.
161.-Front tarsi black from middle of third segment, first three segmentsvery slender,
last two forming an oval, broadly fringed tip to tarsi (Maine; Massachu-
Eetts; New Jersey) ................................. virga Coquillett.
First two segments of front tarsi yellow, last three black, last two segments
distinctly flattened, a little widened laterally, but not fringed; hind
femora and tibiae each blackened on apical third (New York).
abruptus Aldrich.

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Igor, which key have you used?

John, could you make a photo from the ventral side of the hind femur. It looks like ciliated.

Stefan

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He is using the key by Van Duzee and Curran, American Museum Novitates 683 (1934). Using that key I got Dolichopus albicoxa as the closest match. That species differs in extent of darkening on hind tibia and possibly in some hair colors. http://books.goog...p;pg=PA165

I took the hind femur not to be blackened at apex, merely slightly darker brown, but if it is blackened the branch above leads nowhere.

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Stefan, this is the best I can do, propping it up between two #0 pins. I haven't been able to find a source of proper minims (Bioquip is out of stock, and in any case charges outrageous shipping to Canada) - do you know of a European source that would mail me a small package of something like 0.1 mm or 0.15 mm? (also #000 pins would be great for things this small.)

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I have identified the specimen as Dolichopus albicoxa Aldrich using the keys to North American Dolichopus (Van Duzee & Curran 1934, Van Duzee, Cole & Aldrich 1921).

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Many thanks, all. I'm trying to get access to our local entomological library, when I expect to find Diptera merely difficult instead of impossibly confusing!

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John, I suggest to complete the title with the species name.

Stefan

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Done. Many thanks again.

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Stefan -- do you think it matches the description of the species within typical variation? The hind tibia is darkened more than the description says. The fore leg with enlarged tarsomeres 4 and 5 matches, but that's a common modification and there may be some other species with identical ornaments.

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John, I think this is within the range of variation.
"... still always distinctly blackened on inner side"
Stefan