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Picture-winged flies

Picture-winged fly, Merzomyia westermanni, Kilkenny country park, August 7 2022.

John C. writes:

As people might know, there was a ‘BioBlitz’ organised by WODC and TVERC at Kilkenny Country Park on Sunday 7 August. Sue and I went along to a couple of the sessions to see what we could ‘blitz’.

The two sessions we went to were on recording wildlife observations – essential if we want to conserve it! – and the ‘bug hunt’ in the afternoon.

It was a blisteringly sunny afternoon and following this summer’s weather everything was parched and brown, with few plants in flower except wild carrot and parsnip, and a few knapweeds and thistles.

I suppose that there were about twenty of us, including a number of children, on the bug hunt, which was led by Ellen Lee of TVERC. We were given insect nets and hand lenses and spent an enjoyable hour or so sweeping the nets through the vegetation. I have to say that the kids were much better at catching things than we were, especially grasshoppers. Perhaps that’s because they are closer to the ground.

Lesser golden knapweed fly.

I don’t think that we found any very great rarities, although it was nice to find a Roesel’s bush-cricket (with the aid of Sue’s bat detector). However, we did find some picture-winged flies which are rather attractive when viewed through a hand lens or a macro lens. It’s clear why they are called ‘picture winged’.

At the time Ellen wasn’t sure of their exact identification, but since I posted this blog yesterday, with my identifications, Henrietta and Ellen asked Judy Webb her advice and say “It looks like the first one (with the red eyes) is a good record”.

“The first one is unmistakeable – it’s beautiful  Merzomyia westermanni which breeds in ragwort flowerheads but is not common (unlike ragwort), – it’s increasing in records over the past few years so might be Nationally Scarce or just very local. The other fly (with the green eyes) is the Lesser golden knapweed fly and unsurprisingly breeds in knapweed heads.” (Judy Webb)

The Lesser golden knapweed fly (Chaetostomella cylindrica ) causes galls in the heads of Knapweeds; there is an interesting article here .

The photos are a bit fuzzy because they were taken through the walls of plastic specimen bottles (the flies were later released unharmed).

Thanks are due to Henrietta Pringle of TVERC, Rachel Crookes of WODC for organising the event, and Ellen Lee of TVERC and Judy Webb for the insect ID.

John Cobb 11 August 2022

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