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Hello. Can someone clarify how you separate female Tanyptera atrata and nigricornis, please? In the draft British key, it says that atrata has the trochanters orange and females have tergites 1-3 mainly red; while nigricornis has the trochanters black and female tergites 1-2 mainly red.

But in most photos of nigricornis, it has more red than atrata.

For example, compare
Diptera.info - Photo Albums: Tanyptera atrata (female) (1)

with
Diptera.info - Photo Albums: Tanyptera nigricornis (female) (1)

And what about
Diptera.info - Photo Albums: Tanyptera atrata (female) (3)
It has much red on the abdomen, but black trochanters.

Best wishes
John Bratton

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Dear John

Both spcies are extremely variable, but the colouration of the trochanters is decisive. There was a time I could not believe it myself either...


Theo

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Thanks very much.

John