Unknown Fly

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bobhelencoan
Posts: 657
Joined: Thu Mar 12, 2015 6:25 pm
Location: Waverton, Chester

Unknown Fly

Post by bobhelencoan »

Unknown Fly:

Two of these flies hatched from Knapweed flower heads we were keeping for possible micro moths. Have never seen anything like them before. Green eyes, variegated wings. Would love to know what they are.

Bob & Helen Coan

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wirralbirder
Posts: 323
Joined: Thu Jul 31, 2008 9:50 am

Re: Unknown Fly

Post by wirralbirder »

Hi Bob & Helen,

I am no expert but Urophora jaceana looks a perfect fit. It belongs to the Tephritid family (Fruit flies). It is found on Knapweed (Centaurea nigra); the larvae producing galls on the flower head.

Cheers,
Harry

Lupercal
Posts: 27
Joined: Tue Jan 26, 2010 11:58 am

Re: Unknown Fly

Post by Lupercal »

Hi Bob and Helen,

Sorry Harry - right family, wrong species.

It's a female Chaetostomella cylindrica, a common species throughout Britain whose larvae feed in the capitula of many Cardueae, especially Centaurea nigra. Looking at the plates in the RES key, you could be forgiven for thinking it was the closely related Chaetorellia jaceae or C. loricata, to which the wing pattern appears to be a closer match. However, the former is a very local species in SE England and the latter a southern rarity. Fortunately your excellent photograph clearly shows the details of the top of the thorax which lacks the presutural dorsocentral bristles and black basal spots to (almost) all scutal bristles which is characteristic of Chaetorellia species. It is however a perfect match for C. cylindrica, bristles, spots and all, including the lateral basal and apical black spots on the scutellum.

The only surprise is that you have not come across it before if you are in the habit of collecting Black Knapweed seedheads for microlepidoptera. Years ago when working the latter, I regularly used to breed out this pretty little fly.

Cheers,
Bill Hardwick

bobhelencoan
Posts: 657
Joined: Thu Mar 12, 2015 6:25 pm
Location: Waverton, Chester

Re: Unknown Fly

Post by bobhelencoan »

Many thanks to you both. This is the first time we have kept Knapweed flower heads. We have only recently started looking at micro moths and are realising that some flies can be equally colourful and patterned.

Bob & Helen

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