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Massachusetts, USA June 26, 2012. Camera flash caused it to sit back on its rear end.


(Click to enlarge or view on Flickr.)


(Click to enlarge.)

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Looks like a Helina.

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Would you say there are "setulae adjacent to base of posterior notopleural bristle"? If I count bristles correctly there are, and none of the few North American Helina with such bristles looks like this.

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It seems to me Mydaea corni or near

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It is happier in the key to Mydaea. It could be Mydaea neglecta, known from my area. That species is supposed to be close to electa. I don't know what we have here that is near corni.

Quoting the revision of North American Mydaea:

Mydaea neglecta Malloch
Mydaea neglecta Malloch, 1920, Trans. Amer. Ent. Soc., vol. 46, p. 136.

MALE: Length 7 to 8 mm. Very similar to electa Zetterstedt, of which it may ultimately prove to be a subspecies. It differs from it in having the legs yellow, only the coxae, tarsi, and basal half to three-fourths of fore femora infuscated. The anteroventral bristles on basal half of hind femora absent or setulose. Sternopleurals usually 2:2, occasionally with the lower anterior one very much reduced or absent.

FEMALE: Length 7 to 8.5 mm. Similar to the male, differing from it in having the front at vertex one-fifth of head width. Second antennal segment slightly brownish to dark fulvous. The femora and tibiae entirely fulvous. Sternopleurals frequently 1:2 instead of 2:2.

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John, even with specimen in hand, the identification of Mydaea to species level - "it is without me".
In my opinion the Palaerctic Mydaea badly need revision. So, I guess, need Nearctic Mydaea. What is more, Mydaea is cold resistant genus, Beringia land bridge was easily penetrable for Mydaea. Alas, Palaearctic and Nearctic Mydaea live "in the parallel Worlds", nobody has compare it properly yet.

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Nearctic Mydaea were revised in 1949 and boreal North American Mydaea in 1965. But I suppose the task of revising the large genera of Muscidae on a worldwide basis is too frightening.