UK's largest fly spotted in Teifi Valley after 20 years

Natural Resources Wales (NRW) has recorded the presence of the endangered Hornet Robber Fly in a Site of Special Scientific Interest (SSSI) after a 20 year absence.

The Hornet Robber Fly, an important species to the area and to the UK, was last seen in Wales in 2007 but had not been recorded in the Old Cilgwyn & Cae Helsop SSSI since 2003, an area that’s also notable as the site of the last gun duel in Wales.

As one of a number of priority species in the UK Biodiversity Action Plan (UK BAP), conservation efforts have been put in place to improve population numbers and bring the species back from potential extinction.

The species has suffered from a loss of habitat to agriculture and development and because of the Robber Fly’s breeding cycle they are especially affected by the use of chemical treatments in grazing stock.

This particular species of fly lays its eggs in the dung of grazing animals like cows and horses. Chemicals used to treat parasites in these animals can have the added effect of deforming or outright killing the offspring, with even a single poorly timed treatment leading to a huge loss to the population.

By working with landowners and managers and timing the treatment of livestock against the Robber Fly’s breeding season, NRW can lower the risk to the species and help ensure more of the offspring make it to adulthood.

Michael Sneade, conservation advisor for NRW, said:

"The Hornet Robber Fly is one of the UK’s biggest flies and is a top predator in the insect world both as larvae and as adults. They play a large role in keeping the delicate ecological balance and their presence is usually proof that the area has a high biodiversity value.

“The species has been at risk since the widespread use of pesticides to treat internal parasites in livestock and numbers are continuing the dwindle across the UK. We have a special responsibility to ensure this important insect can continue to help the ecosystem function in balance.

“We have worked tirelessly with the landowner at this site to safeguard one of the last strongholds of this particular species of fly in Ceredigion. To see record numbers at this SSSI has been a real joy for us and a clear confirmation that correct management practices really are key to ensuring this species can live and thrive alongside people, now and in the future.”