Mid/late May 2013

The frequently cool, cloudy weather and wet days has not been ideal for hoverflies and other fly families that like to sun bask or take nectar. Craneflies are less badly affected by such weather and the Spring species have been the major component of my forays of the past three weeks. In particular, our local woods have held many of the short-palped cranefly Limonia nubeculosa. This is one of the most easily identified of our craneflies. It is medium sized, with mottled wings and three dark rings on each of its yellow femurs. These three rings are unique in the British cranefly fauna. The large grey long-palped cranefly Tipula oleracea is also very common at present. Another large long-palped cranefly that I am finding at most woodland sites is Tipula varipennis. This has mottled wings, whereas T. oleracea has the typical wing pattern of the Tipula sub-genus: a dark leading edge with a whitish parallel stripe behind. The other really common cranefly about at the moment is the smallish, black hairy-eyed cranefly Tricyphona immaculata.

On the odd warmer days, hoverflies have been more easy to find and more species have been emerging. In the early May blog I mentioned the appearance of the 'Heineken Hoverfly' Rhingia campestris. Its close relative R. rostrata is also on the wing now in our ancient woodlands. The two species can be separated in the field if good close views of them are obtained. On the wing it is very difficult to separate them. The former species has narrow black edges to its abdominal segments (tergites), brown to black legs and a bronzy top to the thorax, whereas R. rostrata has a pure orange abdomen, more orange legs and a bluish grey top to the thorax. This latter species has only been found in Northants for the past few years. It was formerly confined to the South and West of Britain but has been expanding its range North and East. It is now frequent in our local woods, although I have yet to see it in my garden.

                     Rhingia rostrata showing bluish-grey thorax, orange abdomen and legs and long "snout"

Rhingia campestris showing more bronzy thorax, darker legs, black edges to the tergites and slightly longer "snout".

The most interesting hoverfly for me so far has been Criorhina berberina, a very good bumble bee mimic, which I saw feeding on wayfaring tree flowers in one of the Yardley Chase woods. These hoverflies have larvae that feed in rotting tree roots and are associated with ancient woodlands.

Now that the hawthorn is coming out, the St Mark's fly Bibio marci is becoming frequent. This largish black fly can be seen in swarms around the flowers of hawthorn. It gets its name from coming on the wing around St Mark's Day, 25th April. However the late Spring has delayed its appearance and I did not see one until 15th May. Another frequent visitor to hawthorn is the empid fly Empis tessellata. This is a large empid with a long, straight, downward-pointing proboscis, dark in colour with yellowish bases to its wings. It is a predator of other flies but can also been seen drinking nectar at a variety of flowers. I have seen one capture a Syrphus hoverfly and kill it.

                                         
                                                     Empis tessellata

Another very common empid at present is the smaller, yellow Empis trigramma. It gets its scientific specific name from the three dark stripes on top of its thorax. However, that is not enough to identify the species as there is another very similar empid also on the wing E. punctata. The two are separated from each other by the arrangement of bristles on top of the thorax. I have recorded both locally in the last couple of weeks.

Early May 2013

The warmer weather has brought out more blossom and the hoverflies are coming out with them. Around the blackthorn flowers, male Eristalis pertinax are holding territories. There are also many Eristalis intricaria about, more than I have noted in previous years at this time of the season. This is a dark bumblebee mimic.

Last Saturday I noted the first Epistrophe eligans of the year in Old Sulehay forest. This species is one of the iconic Spring hoverflies. Nationally, its appearance has been getting earlier in the year, presumably because of climatic warming, so I wondered if the long cold Winter had delayed its appearance this year. Looking back over the past 10 years of my observations, the first dates for me in Northants were:
2003 11th May
2004 no record
2005 17th May
2006 no record
2007 22nd April
2008 26th April
2009 26th April
2010 27th April
2011 07th April
2012 10th May
2013 04th May.
So it was slightly late but by no means the latest I have recorded it.

Epistrophe eligans, showing the broad yellow marks on the second abdominal segment, narrower ones on the third and no yellow on the fourth.

Another typical Spring species is Leucozona lucorum. I saw my first for the year on 4th May near Yardley Hastings.

Leucozona lucorum, showing the bright white marks on the base of the abdomen contrasting with the black apex. L. lucorum has a yellow scutellum, whereas the similarly coloured Volucella pellucens has a black scutellum.

In the local woods and even in my garden the "Heineken Hoverfly" Rhingia campestris is also on the wing.

We are now seeing the first of the Spring craneflies emerging, with the large long-palped cranefly Tipula oleracea being taken at the Pitsford Reserve's moth traps.

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.

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.

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.

Early Hoverfly

The warm weather at the beginning of the week seemed to wake up a few insects and I have heard of several sightings of butterflies and bees. However, I had to go to a funeral in Suffolk on Tuesday so missed the best of the weather. Back at home on Wednesday I noticed a fly on the inside of the window. On taking a closer look I realised it was a hoverfly and it looked superficially like a Melanostoma. Anyway, I caught it and looked at it yesterday. It was a male and had rounded front tibia and tarsi and yellow, heavily dusted spots on the abdomen. I went through the Melanostoma key and it failed on abdomen shape and dusting on the frons. It also did not look right, with a fairly inflated frons and face. Going through the Platycheirus key it failed again. However, I remembered that Platycheirus ambiguus is an early species and has rounded front tibia and tarsi, so I tried that part of the key (ie abdomen with silver/bronze spots not yellow spots). It keyed out perfectly. I then checked in van Veen's key to the Northwest European hoverflies and again it keyed out. In this key it does say that the abdominal spots can be dusty yellow. One of the characteristic features of this species (and shared with only one other NW European hoverfly) is the curled bristly hair at the apex of the front femur and that was present on my specimen to confirm it. Platycheirus ambiguus is not well recorded, probably because of its early flight season. It is best searched for flying high around blackthorn when it is in flower. Peak records are from around the end of April, so this is still an exceptionally early record. I have found it locally around blackthorn and flowering fruit trees in late April so keep a look out for it.

That species has brought my garden total for hoverflies to 34. Must try harder!

With the change back to cold, damp weather and colder weather forecast, I suspect there will be no more hoverflies around for a while. However, the pussy willow buds are just starting to open in sheltered spots and they should provide nectar and pollen for the first few hoverflies of the season. An early hoverfly to look out for at sallow blossom is Cheilosia grossa. I have no records of this species, although it probably occurs locally. Its tendency to fly high and early in the season probably means it is overlooked. It is apparently more easily detected as a larva developing in the base of thistle stems later in the season. Stuart Ball has produced a guide to finding it and Cheilosia albipila. The guide can be downloaded from the Dipterists Forum website at:
http://www.dipteristsforum.org.uk/t104-Recording-Cheilosia-larvae-from-thistles.html

Early March

When I was making artificial rot holes in the stumps at Pitsford Reservoir, I took a winter gnat from the moth trap. It was a female and I struggled to identify it. However, at the Dipterists Forum workshop, I asked Alan Stubbs if he could take a look and he immediately identified it as Trichocera regelationis. This is a common species but not recorded at Pitsford before. Alan explained the identification features. The Dipterists Forum workshops and field meetings are great opportunities to pick up tips from the experts.

In May the DF will be holding a Spring field meeting in the Rockingham Forest area where we will have the opportunity to visit some really good sites. If anyone is interested in coming along contact me or Roger Morris and check out the DF website.

 On Sunday, I visited Pitsford but it was very quiet. However, I did check out the artificial rot holes in water bottles that I had put up a few years ago. One of the bottles had a rat-tailed maggot, the larva of a hoverfly from the Eristalini tribe. It is probably Myathropa florea. One of the bottles was too dry for use by flies but the others looked to be suitable.

 There are a few flies starting to be active now the weather is warming up. Anthomyids are among the first Spring flies but I find them very tricky. I was advised at the DF workshop to only attempt males and the easiest approach is to expose the genitalia and compare them to the diagrams in Ackland's key. The key itself can then be used to confirm identification. On that basis I shall try to record some of these species this year.

 The UK Hoverfly Recording Scheme's big hoverwatch project that attempts to use constant effort recording to track changes in hoverfly numbers and distribution got off to a soggy start last year. Let's hope we have better conditions this year. The Wildlife Trust also want to use the same technique on some of their reserves so it is an opportunity to contribute to two projects with one survey if a Trust reserve is chosen as the site. Details can be obtained from Roger Morris on the Hoverfly Recording Scheme's website or from me or Henry Stanier for the Wildlife Trust's project.