The largest fly found in the UK has been seen buzzing around the Teifi Valley after a Hornet Robber Fly was spotted in the Old Cilgwyn and Cae Heslop Sites of Special Scientific Interest (SSSI), which is in Ceredigion.

The endangered Hornet Robber has been described as an important species to the UK as a whole, and was last seen in Wales in 2007. It has not been recorded in its current Ceredigion location, however, since 2003.

“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,” commented Michael Sneade, who is a conservation advisor for Natural Resources Wales.

“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,” continued Michael Sneade, “and we’ve 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.”

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.

The Hornet Robber fly can grow to up to 2.5cm in length and can be spotted between June and October.

It has a brown thorax and a black-and-yellow abdomen and there are currently 28 species of robberfly in the UK. The Hornet robberfly is one of the largest.