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Unknown Fly
Posted: Tue Apr 04, 2017 9:36 am
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
Re: Unknown Fly
Posted: Tue Apr 04, 2017 9:18 pm
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
Re: Unknown Fly
Posted: Wed Apr 05, 2017 10:33 am
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
Re: Unknown Fly
Posted: Wed Apr 05, 2017 11:15 am
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