SUFFOLK DIPTERA CHECKLIST
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DIPTERA REPORT 2024 PETER VINCENT During August the movement of sheep and cattle was restricted in Norfolk and Suffolk after several confirmed cases of bluetongue disease. As a result, the Department for Environment, Food and Rural Affairs put in place a restricted zone to mitigate the risk of further cases of disease occurring. Further cases have now been reported and the current (November) restricted zone covers much of eastern England as far north as Yorkshire. Bluetongue is an insect-borne viral disease to which all species of ruminants are susceptible, although sheep are most severely affected. Cattle and deer are less likely to show clinical signs but are thought to be important ‘reservoirs’ of the virus. It does not affect humans. The impact on susceptible animals can vary greatly – some show no clinical signs or effects while for others it can cause productivity issues such as reduced milk yield. It can cause infertility and breathing problems in sheep, cattle and goats. In the most severe cases, it can kill infected animals. This is bad news for livestock farmers, both economically and emotionally as no wants to see their animals suffering, but what of the insects that carry the bluetongue virus? These are flies of the Ceratopogonidae family and, more specifically, flies of the Culicoides genus. The Ceratopogonidae form a family of small nematocerous flies, usually less than 4mm, dark in colour, with broad wings. They are best known as ‘biting midges’ but are also called ‘sand flies’, ‘biting gnats’ and in America as ‘no-see-ums’. These are familiar and plentiful insects - as anyone who has been to Scotland in summer and encountered the Highland midge Culicoides impunctatus Goetghebuer, 1920 will quickly testify. Biting midges breed in damp organic matter such as soil, leaf litter, compost, and animal dung (different to mosquitos who breed in water such as ponds). Female midges feed on the blood of vertebrates, including humans, to get protein for egg-laying and are responsible for the transmission of arboviruses of livestock such as bluetongue. Biting midges are short-lived, producing multiple generations per year with populations that fluctuate annually between periods of high and low adult abundance. In normal conditions they are only capable of short distance dispersal, usually within 1km of their breeding site, but many species, particularly during periods of high abundance, exhibit long-distance wind aided dispersal. Flights of infected Culicoides on prevailing winds have been inferred to reach several hundred kilometres in a single night over water bodies (Burgin, Gloster, Sanders et al., 2013). Culicoides obsoletus Trans. Suffolk Nat. Soc. 60 (2024)