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.

Monday, 15 April 2013

Mid April 2013

The milder weather over the weekend should have stimulated some hoverfly activity. I spent the weekend helping with wetland invertebrate monitoring in the Nene valley, so did not get chance to hunt for hoverflies. However today I had a good look round the garden - nothing found, so I visited Stoke Wood in the afternoon. Although there was a stiff breeze blowing, the main ride was sheltered and catching the sun when it appeared.  There were plenty of primroses and wood anemones to provide nectar and some sallows were in flower too. I did not see a single fly visiting flowers! However, I did find Eristalis tenax, the drone fly, sunning on the ride edge. The only other hoverfly I found was Ferdinandea cuprea which was sitting on a newly cut stump. This species is associated with ancient woodlands, where its larvae live in sap runs. It is not a frequent visitor to flowers and is more often seen on tree trunks or logs.

Eristalis tenax, the drone fly

Ferdinandea cuprea

Apart from the two hoverflies, there were a few common yellow dungflies Scathophaga stercoraria and the odd anthomyid fly. Other wildlife included a common toad, a peacock butterfly, singing chiffchaff and green woodpecker. Over the field on the track into the wood a single buzzard circled and three lapwings flew across.

With only four species of hoverfly to date, I felt that it had been a slow start to the season but, looking back to last year, when we had a good start to the Spring, I had only seen 4 species by mid April then. I had received records of another 3 species from other people, whereas so far this year I have no other hoverfly records. So, despite the cold weather, things are not so bad.

Friday, 5 April 2013

Early April 2013

I have been away in Sri Lanka for a couple of weeks and coming back to snow was a bit of a shock. It is still too cold for much insect activity but there are a few things to report.

Firstly, the Cranefly Identification Workshop, run by John Kramer at Pitsford Water's Holcot Lodge went well with 11 attendees. John gave a well illustrated introductory talk to the cranefly families before we got stuck in to the keys, using John's reference collection. It was also an opportunity for John to get some feedback on these draft keys so they can be revised for publication. Updates will be posted on the Dipterists Forum website from time to time.

Secondly, Roger Morris and Stuart Ball's new WildGuide to British Hoverflies arrived through the post. I am very impressed. The photos illustrating key identification features are generally first class. I am sure it will convert many people into identifying hoverflies. There is much detail in the well-illustrated text that will be valuable not only to beginners but to experienced dipterists as well. It is particularly good at helping with field identification.  It does not replace Stubbs and Falk's British Hoverflies, which is much more comprehensive, but it does complement it very well.

On the subject of Hoverflies, the Wildlife Trust for Beds, Cambs and Northants will be continuing its Hoverwatch monitoring work at Old Sulehay this year. If anyone is interested then do get in touch with me or Henry Stanier at the Trust's Cambourne office. We are also looking out for people who would like to set up a constant effort hoverfly monitoring site on any of the Trust's reserves. This is basically the same as the "Big Hoverfly Watch", described by Roger Morris in the Bulletin of the Dipterists Forum. The only difference is that for the Trust sites is that we want a visit in July as well as May and June. The same survey can be used for both projects. In preparation for the Hoverwatch and constant effort projects I shall be running a one day workshop at Ring Haw field centre on April 27th.. If anyone is interested in attending please contact me or Henry Stanier.

I have not found any flies of interest locally, but Mike Killeby has been beating dead leaves and branches of pines on our forays on the Compton Estate. He has passed the flies on to me for identification. The most interesting were 3 picture-winged flies found Denton Wood on 14th March. These keyed out to Tephritis matricariae. A number of these gall-forming flies over-winter as adults and emerge in the Spring to lay their eggs on the developing host plants.

Yesterday Mike gave me a window gnat, which keys out to be a male Sylvicola cinctus. This is probably the most common member of the genus, although many books illustrate what is claimed to be Sylvicola fenestralis. This latter species is not common and has been misidentified in a number of publications. Indeed my attention was drawn to it by Jon Cole when I listed S. fenestralis in one of the newsletters. He sent me a paper showing the differences in genitalia. I have re-examined my specimens using this paper and they have all proven to be S. cinctus. I urge anyone who thinks they have S. fenestralis to double check. For females it is necessary to exert the genitalia a little. With dried specimens this means relaxing. I put the specimen in a jar with some damp tissue in the bottom, the specimen should not be in contact with the damp paper. Left tightly sealed overnight, the specimen was quite flexible and I was able to work on it without bits shattering all over the place.