Wednesday, 22 July 2009

Notes from Early July 2009

The immigration of thousands of Painted Lady butterflies into the UK has been well recorded but hoverflies are also migratory and we have seen a large increase in the very common Marmalade Hoverfly, Episyrphus balteatus, in the last couple of weeks. In past years, when this has happened there have been hysterical headlines in the popular press about mass invasions of wasps, although they were in fact hoverflies and completely harmless (unless you are an aphid!).

On 2nd I visited a local spring-fed marsh. In just over half an hour I found 5 species of Soldier Fly there. Oxycera nigricornis (Delicate Soldier), Oxycera rara (Four-barred Major), Nemotelus pantherinus (Fen Snout), Oplondontha viridula (Common Green Colonel) and Chloromyia formosa (Broad Centurion) were present in good numbers. Apart from the widespread Broad Centurion these are not well recorded in the county.

I found a Tachinid Fly, Sturmia bella, in the south of the county on the 9th. This is an introduced species, believed to have entered the country via someone importing larvae of Vanessid butterflies. It is a parasitoid of these butterflies and may be linked to the recent decline in Small Tortiseshell.

On 10th/11th I took part in a survey for the Wildlife Trust of a damp meadow area in Northampton. The weather conditions were poor so not much was found but I was pleased to find another Soldierfly, Pachygaster leachii (Yellow-legged Black Soldierfly) and the Hoverfly, Eupeodes latifasciatus. This latter species is believed to be partially migratory. It is widespread but scarce and fluctuates in numbers from year to year. It is associated with rushes in damp meadows. A couple of common snail-killing flies, Sciomyzidae, were also found: Ilione albiseta and Pherbina coryleti.

Sunday, 28 June 2009

Putting Flies on the Northants Map

Diptera are true, or two-winged, flies. They do not have a good press. In some cases that is well-deserved: tropical mosquitoes transmit diseases that kill more humans than any other animal; blow-flies and bluebottles cause food poisoning and other diseases through transmission of bacteria in food; agromyzids and anthomyzids are important pests of food crops whilst midges, blackflies and horse flies can ruin a pleasant day in the country with their bites.

But this is only part of the story. In 2008 the 7000th species for the UK was discovered and of these 7000 species the vast majority are not harmful and many provide important benefits for humans and other wildlife. Hoverflies are important pollinators and some of their larvae are major predators of aphids. Empids and Dolichopodids are predators of other small flies; tachinids or parasitic flies kill millions of moth larvae, which would otherwise defoliate plants.

So, knowing what flies we have and where they live is important in understanding our environment. In Northants we do not know how many species there let alone where they live or whether any have any real impact on our environment. Even the most popular and widely recorded flies, the hoverflies, are poorly known in the county. Indeed in the national atlas of hoverflies published in 2000, Northants does not show as many records as surrounding counties. This is almost certainly due to lack of recording rather than missing species. The position is almost certainly worse with other fly families.

The Northamptonshire and Peterborough Diptera Group was formed recently to allow those people in the area with an interest in flies to share information and to help each other with identification and recording in the old vice-county of Northamptonshire (Vice-county 32). We welcome anyone with an interest in any group of flies to join us in field meetings and workshops. If you interested please let me know. All our records are given to the Northamptonshire Biological Records Centre and, where one exists, the national recording scheme for that group of flies.