Sunday, 28 April 2013

End April 2013

The warmer weather in the middle to end of the week has produced more activity. In particular bee-flies have been numerous at several sites I have visited over the past few days. My first record of our commonest bee-fly, the dark-edged bee-fly Bombylius major was on 20th April in my garden. What a contrast with last year, when my first garden record was on 25th March! Locally, we only have one species of bee-fly, but there are 9 British species, although most are rare. One other, the dotted bee-fly Bombylius discolor could turn up locally. It has been recorded in Warwickshire. It is easily recognised as a bee-fly with spots all over its wings, hence its common name. It is more likely to be found in areas where there is sandy or chalky soil where its mining bee host can be found.

Two images of the dark-edged bee-fly Bombylius major. The upper image shows one hovering whilst drinking nectar from a wood anemone flower in Stoke Wood, whilst the lower shows one at rest in my garden. The dark front edge of the wing, which gives it its common name, is clearly visible in both photos.

The fly is a larval parasitoid of the larvae of some solitary bees. The female fly gathers sand into a special chamber in her abdomen where she mixes it with her eggs. She then finds an area of bare ground where the host is likely to nest and, whilst hovering over it, she flicks the egg/sand mixture at the ground. When the fly larva emerges it enters the nest and finds an open bee larval cell and enters it. The fly larva waits for the bee larva to grow then it attaches itself to it and feeds on the bee larva's body fluids, killing it in the process.

Apart from bee-flies, there have been a few species of hoverfly about locally. This past week I have seen four species of Eristalis - pertinax, tenax, arbustorum and intricarius. The last one is a blackish bumble bee mimic, whereas the others are more like drone honey bees. Also noted have been Syrphus torvus, Platycheirus albimanus, Melanostoma scalare, Cheilosia pagana and Cheilosia chrysocoma. This last species is not at all common. It flies early in the year, which may mean that it is missed. I usually record it between mid April and mid May. It is a very attractive fly, with rich foxy-red hair over its body. It is usually found sitting on dead leaves or branches on the ground in a sunny spot. The photo below was taken by Keith Walkling in a local wood.
Cheilosia chrysocoma male photographed by Keith Walkling.

If anyone thinks they have seen this species locally I would be interested to know. A photo or voucher specimen of it would be needed to confirm the record.

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