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Is this fly a Shore Fly, Ephydridae? He was indeed on the shore, of a large pond in the mountains. West Virginia USA, 16 August 2006.

Size was 5.3 mm. Such unusual eyes!

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Hi Stephen
Certainly Ephydridae. Probably Parydra.

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How long time to grasp with sure about ID families? :)
Sometimes it is easy to see which family but most of the time it seems not be so easy. About spiders: to arrive family ID is, almost times, very easy. :)

So, I will try to appoint the principal features that we must pay attention when we are seeing a dipter. I wish, at least, arrive to genus level for dipter. :))) But just when I know almost all families... it take a lot more time in relation to spiders.... I think. :)

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First of all, I agree with Tony's comment: Probably Parydra



Almost everything is easy if you practice hard enough :) For me spider ID to family level seems very very difficult.

For me the diptera took two years and some 10.000 more-or-less random identified specimens. Some family divisions are not very well -defined in external characters (Anthomyiidae/Muscidae or Hybotidae/Empididae) - they are mostly based on structure of male genitalia. I'd say that genus level is easier than family, since species of most genera share most obvious characters while many families display a huge range of sizes, colour and shapes and proper identification of the family rely on small or obscure characters.

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Tony, Kahis, Thanks for your help with this one!