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The Society for the study of flies (Diptera)

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#1 2008-06-01 23:56:28

Judy Webb
Committee
Name: Judith Webb
Registered: 2008-02-21
Posts: 422

Sphaerocerids with reduced wings

I found some weird flies in a pitfall trap recently.  Unfortunately a vole drowned in it (I have changed the trap position and secured the lid) but in the trap with the dead body were 4 flies that looked like ants (same shape and size as common black garden ants) but very bristly and on closer examination I can see they have little wing stubs.  From their tarsi I'm guessing they are Sphaerocerids (flattened first tarsal segments on hind legs).

Anybody met this kind of fly before?  I'm searching through my resources for a key, but would welcome advice on how difficult or not they might be to identify.  Also, anybody know if they really were attracted to the dead vole or is this just a coincidence they were all in this particular trap?

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#2 2008-06-03 21:34:01

schultmay
DF Members
Name: Barbara Ismay
Registered: 2008-02-14
Posts: 132

Re: Sphaerocerids with reduced wings

Dear Judy,

Your short winged fly is almost certainly Crumomyia pedestris, Sphaeroceridae, which is found in grass tussocks and fen. They are attracted to decaying organic matter, but I am not sure if the larvae are known. It is not a common fly, and I considered it for Nationally Scarce status, but there are quite a few records and the short wings must mean it is under-recorded.

You'll have fun keying it out as the keys depend on venation, which is optional (some specimens have longer wings) in this species. Pitkins RES key is the best source for Sphaeroceridae in general, but nearly 20 species have been added since.

Best wishes,
John

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#3 2008-06-04 15:20:55

Judy Webb
Committee
Name: Judith Webb
Registered: 2008-02-21
Posts: 422

Re: Sphaerocerids with reduced wings

Thank-you, John.  Just last night I was looking through my Dipterists Digests and came across a paper on Crumomyia pedestris by B A Woodcock and D J Mann (DD 2004, 11,103-106) in conservation field margins and it seemed very likely to me to be the ones I have found. Without wing venation, I'll have to wait until I can compare my specimens with some in Diptera collections, I suppose.  It is still an interesting possible find.

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#4 2008-06-19 04:31:10

schultmay
DF Members
Name: Barbara Ismay
Registered: 2008-02-14
Posts: 132

Re: Sphaerocerids with reduced wings

Why don't you bring it over when you bring your microscope?

B.

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