More on Horseflies

Following on from Kim and Neil's record of a female Tabanus autumnalis at Summer Leys, Dave Jackson sent me a picture of another there, but this time a male. In many species of flies, but not all, the males can be distinguished from the females by having holoptic eyes - that is the eyes meet along the top and front of the head. Females are always dichoptic - having a separation between the eyes. Here is Dave's photo:

 Tabanus autumnalis Large Marsh Horsefly (c) Dave Jackson

I mentioned in the previous blog some of the smaller, more common species of horsefly (family Tabanidae) so I have added a couple of examples below. 

Chrysops relictus Twin-lobed Deerfly (c) John Showers

The above horsefly is one of the usual culprits when a nice walk in the country is spoilt by biting flies. They can be very persistant. It tends to like damp places, marshes and damp woodlands are favoured. I was once driven off doing a dragonfly count at Pitsford's Holcot Bay by deerflies attacking me. There are very similar other species that occur locally but in much fewer numbers so I always try to take one or two for closer examination.

Hybomitra bimaculata  Hairy-legged Horsefly (c) John Showers


Notice the eye patterns on the horseflies. They all have coloured eyes and some have distinctive bands or spots. These patterns fade on dead insects so you need to see them live and up-close and personal to appreciate their beauty! These patterns are useful clues to identification so worth noting.

Last Saturday we held our late June Hoverwatch survey at Old Sulehay Forest and Graham Warnes caught another of the medium sized horseflies there Hybomitra bimaculata Hairy-legged Horsefly. These are usually found in woodland rides. I have also found this species at Yardley Chase. Often the males can be seen hovering a few feet off the ground in bright sunshine. They are holding territories to await or attract a passing female.

Summer Leys horsefly

I received an email from Neil Hasdell on monday saying that he and Kim Taylor were walking round the reserve when Kim saw a large insect alight on a fence post. They quickly investigated and Neil realised it was a large horse fly about 20 mm long. He sent me his photos for identification. 

From the photos and size I suspected Tabanus autumnalis but as this is a very scarce species in this area, I sent the pictures to Martin Harvey, who runs the Soldierflies and Allies Recording Scheme. He is happy that it is T. autumnalis, but said that if seen again a specimen should be caught and the underside of the abdomen checked for a dark longitudinal stripe. This is diagnostic. It is only the third record for Northants.

This species is considerably bigger than the more locally common horseflies like T. bromius and Hybomitra bimaculata or the even smaller clegs and deerflies. It is generally the smaller species that are a pest to humans. The larger ones consider us too small! They generally go for cattle and deer. One good way of finding horseflies on hot days is to leave the door of your car open in a sunny area near to where there are cattle. The flies home in on infrared radiation from hot bodies and will enter the car, where you can easily (hopefully!) trap them. Alternatively, if you don't want horseflies in your car, keep the doors shut. At a field meeting of Dipterists Forum at Speyside we parked in a lay-by on the Glen Feshie road and immediately had the giant horsefly T. sudeticus investigating the front wheel arches of the car, attracted by the heat from the engine compartment. Incidently, horseflies tend to be attracted to dark objects, so wearing light coloured clothes when out in suitable habitat may reduce your chances of being bitten.

Tabanus autumnalis (c) Neil Hasdell. Note the eyes do not have any bands across them. The similar, but smaller T. bromius has a single coloured horizontal band. More of Neil's photos below.

May 2014

After a good early start to the season, May was fairly slow-going for hoverflies. The highlight for me was seeing two Criorhina ranunculi in Scotland Wood. I first noticed one hovering close to the ground at the base of a large Douglas Fir. It had whitish hairs on the rear end. It kept settling briefly on a bramble leaf, where I managed to photograph it, and then returning to hover close to the base of the tree. At one point, a second fly joined it and they briefly tussled in mid-air, dropping to the ground. Almost immediately the visitor flew off and I never saw it again. The visitor had yellow hair at the apex of the abdomen. This is a colour variant, mimicing the red-tailed bumblebees.

Criorhina ranunculi

A visit to Irthlinborough Lakes with the Northants Diptera Group at the beginning of the month produced the hoverflies Anasimyia transfuga and Platycheirus fulviventris in the damp areas adjacent to the lakes. Several craneflies were found, including Tricyphona immaculata, Erioconopa trivialis and Phylidorea ferruginea. The following week we visited Ramsden Corner for the first time. The weather was not promising and the flies were hard to find. Two long-palped craneflies were found: Tipula varipennis and T. vernalis.

We did not have a local field meeting the following weekend as most of the group joined the Dipterists Forum Spring Weekend in Dorset. The hot weather there meant that hoverflies were hard to find but we did manage to see Microdon myrmicae at the RSPB reserve at Arne. Unfortunately, no Microdon species have been recorded in Northants. This weekend coincided with the Bioblitz at Halse Copse, organised by the Northants Biodiversity Records Centre. I made a belated visit during the following week. The temperature had dropped somewhat but was still suitable for finding flies. I did not find anything unusual during my visit but managed to add a few records for the site. These included a male empid fly, Empis bicuspidata, which I have not seen before. There were several species of long-legged fly (Dolichopodidae), including Dolichopus ungulatus, D. plumipes, D. popularis, D. longitarsis, Argyra diaphana and Chrysotus gramineus.

The moth traps at Pitsford continue to provide a steady stream of flies in the by-catch. These inluded the tiny metallic green soldierfly, Microchrysa flavicornis.

End April 2014

The second half of April has not been as productive for hoverflies for me. Our first Diptera Group meeting of the year at Ditchford Lakes and Meadows only produced three species. The near ubiquitous Melanostoma scalare was swept from near a hedgerow. Anasimyia transfuga was swept off lakeside reed grasses and a single Lejogaster metallina was swept out of the wet marshy area in the meadow. I found my first big-headed fly (Pipunculidae) of the year here - Dorylomorpha haemorrhoidalis. This area was much more productive for dung flies and their allies (Scathophagidae). Sweeping over the really wet areas produced Scathophaga stercoraria, S. inquinata, S. suilla, S. furcata, Nanna inermis and Trichopalpus fraternus. Snail-killing flies (Sciomyzidae) in the marsh were the distinctive Sepedon sphegea and Elgiva solicita. Three empids Rhamphomyia crassirostris, R. sulcata and R. pilifer and a few common craneflies made for a good start to our field meetings.

Pete Sharp gave me a parasitic fly (Tachinidae) that he had raised from the pupa of lunar yellow underwing Noctua orbona taken at Lakenheath in Suffolk on 12th April. It turned out to be Pales pavida. The lunar yellow underwing is not listed as a host for this fly but other Noctua species are given. I am always happy to try to identify parasitic flies that the lepidopterists find when raising larvae. Pete has provided me with some good records of parasitic flies and their hosts and I pass on all the details to the Tachinid Recording Scheme.

The Pitsford Reserve moth traps are yielding a good number of flies now. Craneflies seem particularly attracted to the lights and up to the end of April there had been several Tipula oleracea and T. vittata. The small cranefly Trimicra pilipes was taken several times in the trap by the water's edge. This distinctive species has very hairy legs, particularly in the male. It is associated with draw-down zones of water bodies so Pitsford is probably an ideal habitat for it.

Mid April

This sunny weather has certainly brought out far more insects than I usually see at this time of the year. Hoverflies started slowly but are now appearing in good numbers. Kev Rowley took Melangyna lasiophthalma at Pitsford and the moth trap there caught Parasyrphus punctulatus. A trip to Wakerley Great Wood with Roger Morris on 1st April produced a number of species visiting sallow blossom. Apart from the two species already mentioned, Roger found several Platycheirus discimanus. I was unable to catch these as my net handle was too short. They congregate high up, which probably explains why we get virtually no records of this species. There were also several Criorhina ranunculi visiting the sallow blossum. Apart from the hoverflies, Roger also found the furry tachinid Tachina ursina.

My garden is rather exposed to the wind but a trickle of hoverflies have been visiting. I am keeping a near daily count to send to Roger at the end of the season to contibute to his monitoring project. If you are interested in taking part details are on the Facebook UK Hoverflies pages. My first Epistrophe eligans of the year was on 9th April in my garden and this week it has turned up at several sites.

The first bee-fly Bombylius major for me this year was also in my garden on 29th March. They are prolific this year, as are the mining bees whose nests they parasitise. I took the following photos at Pitsford last week.

Craneflies are just starting to emerge. The moth trap at Pitsford took Tipula oleracea on 9th April and on 16th I found several Tipula vittata by a stream at Sulby Gardens. Whilst there I also found my first Rhingia rostrata for the season. It is amazing how quickly this species has spread across the county. When I started looking at hoverflies  around the millenium it had not been recorded in Northants and was considered to be a species confined to the extreme South-east and Wales.

End of March

It has been a fairly mixed few weeks, typical of March, with some warm sunny days and some cold and wet ones. Needless to say, the Diptera have been patchy.  Eristalis tenax has shown up in my garden a few times and I have seen the odd one out in the countryside. My first Eristalis pertinax for the year was on 24th March in my garden. At the same time I saw a small Bacchini species of hoverfly but it disappeared before I could get a decent look. The only other hoverflies I have heard about this year were a Melangyna lasiophthalma, taken by Kev Rowley at Pitsford and a Parasyrphus punctulatus found at Harlestone Heath by Jeff Blincow. With the blackthorn and sallows now in full bloom more should be turning up now.

My first bee-fly Bombylius major of the year was yesterday in my garden. It was visiting Aubretia flowers. 

Another greenbottle-like Muscid fly Neomyia viridescens, was found at Yardley Chase. It was visiting coltsfoot flowers. Also at Yardley Chase have been the Tephritid flies Tephritis formosa and T. neesii.

My first snail-killing fly of the year was Hydromya dorsalis, swept from a marshy area in Achurch Meadows on 21st March.

More On Picture Winged Flies

My previous blog mentioned a couple of picture winged flies that I had beaten from conifers. A few days later Mike Killeby gave me some flies that he had beaten from a yew in Yardley Gobion churchyard in January. Amongst the specimens were two more picture winged flies from the Tephritidae family: Tephritis formosa and T. hyoscami. Below are some examples of this attractive genus.

Pictured from left to right are: Tephritis formosa, T. vespertina, T. hyoscami and T. matricariae.

Their main host plants respectively are: sow-thistles, cat's ears, welted thistle and mayweeds where they form galls in the flower heads. If you want to find out more about these flies there is an RES handbook to the Tephritidae by I. White and an excellently illustrated book in Dutch by John Smit.

Apart from the Tephritid flies, Mike also found a Muscid fly (house flies and relatives) Eudasyphora cyanella, which is bright metallic green so could be mistaken for a greenbottle. Also he caught a cluster fly Pollenia griseotomentosa, a wood gnat Sylvicola cinctus and a couple of frit flies, Chloropidae, for which I do not have a key.

Today I saw my first hoverfly of the year in my garden. It was the drone fly Eristalis tenax. This is usually my first hoverfly of the year. As the sallows start to flower in March a few species of hoverfly should be on the wing.