Diptera report 2016

HYMENOPTERA REPORT 2015–16

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DIPTERA REPORT 2016 PETER VINCENT Has 2016 been a good year for flies? The honest answer is that I do not know.

Certainly, there have been a good number of flies around and I have seen and caught a number of interesting ones. The warm dry summer certainly suited some flies, while others thrive in cool wet conditions and so swings in weather conditions tend to balance out. In common with other groups of insects, many species of Diptera exhibit fluctuating fortunes in their populations over the years and it is clear from the historic records that some come and go, and there are often peaks and troughs, sometimes separated by many years. To accurately assess status and population trends in diptera it would be useful to have a monitoring scheme however, as for most invertebrate groups this is not straightforward undertaking, for unlike birds or even butterflies it is not possible to count all the flies along a transect. Even for a comparatively easy to identify family of flies such as Syrphids (hoverflies), it would be a difficult task to even make a reasonable estimate of numbers of particular species as they are often small and mobile and frequently elusive.

Some uncommon Suffolk species I have recorded recently include, the Dolichopid, Dolichopus planitarsis Fallén, 1823, the Empids, Hilara brevistyla Collin, 1927, H. fuscipes (Fabricius 1794) and H. quadrifasciata Chvála, 2002, the Lauxaniid, Sapromyza quadricincta Becker, 1895, the Micropezid, Neria commutata (Czerny, 1930), the Psilids, Chamaepsila buccata (Fallén, 1826) and Loxocera aristata (Panzer, 1801), the Sciomyzid, Tetanocera robusta Loew, 1847, the Tephritid, Tephritis bardanae (Schrank, 1803) and the Limoniid and Tipulid craneflies, Erioconopa diuturna (Walker, 1848), Tipula couckei Tonnoir in Goetghebuer & Tonnoir, 1921, T. helvola Loew, 1873 and T. obsoleta Meigen 1818.

These flies have rarely or have not been recorded in Suffolk (VC 25 and 26) to the best of my knowledge, although the Suffolk species list is far from complete.

A mention to anyone that you are interested in collecting flies usually results in a discussion along the lines ‘well you can come round to our house, we have plenty!’ In the summer these are usually the Muscids, Musca domestica Linnaeus, 1758 - the Common Housefly, with numbers of M. autumnalis De Geer, 1776 building up in the autumn just as the M. domestica population is declining, and hibernating for the winter; although either or both species can occur indoors at anytime. However, there is some evidence that although still common and widespread these flies especially M. domestica are not anywhere as common as they used to be. They are certainly not well recorded species in Suffolk, with only five records of M. domestica, of which four records date before 1945 and seven of M. autumnalis. The identification of this pair, especially males is straightforward - male M. domestica has a yellowish abdomen with dark midline and some irregular dark markings on the sides, whereas the surprisingly striking M. autumnalis has a black abdomen with bright orange patch on each side.

Perhaps the most common fly found indoors is Fania canicularis (Linnaeus, 1761) Lesser Housefly; it is not a muscid but belongs to the Fanniidae family. The flies, slightly smaller than the Muscids are best known for its habit of entering buildings and circling around the light fitting near the centre of rooms.

Trans. Suffolk Nat. Soc. 52 (2016)

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Suffolk Natural History, Vol. 52

In my experience another fly related subject that soon gets brought into the conversation is that of Cluster flies. Perhaps it is the number of old timber framed buildings we have in Suffolk, although they also occur commonly in modern buildings, but many people do seem to suffer and worry about plagues of slow moving and dying flies in their sunny upstairs rooms and attics. Cluster flies are the genus Pollenia belonging to the Calliphoridae, the same family as bluebottles, greenbottles and blowflies. However, instead of the larvae developing in decaying carrion as in most Calliphorids, Pollenia parasitise earthworms, where the eggs are deposited on the soil and the larvae burrow into earthworms on which they feed. They can be recognised by irregular light and dark grey areas on the abdomen and yellow crinkly hairs over the top and sides of the thorax, which can give the appearance of a golden sheen.

What the Cluster flies are doing, is not coming into the houses to breed but rather in autumn they are attracted often in great numbers to the sunny sides of buildings in search of protected over-wintering sites, then on warm days they become active and crawl out of wall voids and attics in a confused attempt to go back outside. Hence the report of hundreds of dying flies in bedrooms. Not all of the eight species of Pollenia on the British list are ‘clustering’; although Pollenia rudis (Fabricius, 1794) seems to be the main clustering species; P. pediculata (Macquart, 1834) and P. angustigena Wainwright, 1940 are also clustering species. The Suffolk list consists of five species with the great majority of records refer to the three clustering species mentioned.

The third group of flies that seem to distress the general public are fruit flies Drosophila. I have no evidence to support this claim, but I suggest that fruit flies have become more of a nuisance in recent years. There seems to be more of them around the fruit bowl and worse still dropping into our beer in the pub. The three Cosmopolitan domestic species Drosophila melanogaster Meigen, 1830, D. immigrans Sturtevant, 1942, and D. simulans Sturtevant, 1919 are the most common fruit flies found indoors where they are attracted by fruit and fermented drinks. Of the small number of indoor collected specimens I have checked, the majority are D. melanogaster, with a few examples of D. busckii Coquillett, 1901. As far as I can ascertain no Suffolk records of these domestic species have been published, perhaps all Suffolk dipterists have all been too busy wielding their nets in the great outdoors to concern themselves with flies in their fruit bowl.

I am afraid I have only recently realised that messages sent to me via my recorder’s email address on the SNS website have not been reaching me. If anyone has sent me a query through diptera@sns.org.uk and has not received a reply, then I must apologise, I was not intentionally ignoring them, and if they would like try again I will reply and endeavour to answer their question.

Peter Vincent 10 Laxfield Road, Fressingfield, Suffolk IP21 5PT

Trans. Suffolk Nat. Soc. 52 (2016)