Swarms of insects forced sun-seekers off the beaches along the coast of East Anglia at the weekend.
Swarms of hover flies drove sun-lovers from the beaches
The Harwich area of Essex was one of the worst-hit places where there was a huge surge in hover fly numbers.
The insects - which look like wasps but are harmless - were also reported in large numbers at sites in Suffolk and Norfolk as well as inland at Cambs.
Wildlife experts said numbers have increased as the insects the larvae feed on have thrived this year.
Andy May, of the Essex Wildlife Trust, said the larvae's main source of food, aphids, had thrived in the warm and wet conditions which in turn has led to an explosion in the hover fly population.
He added the flies had been congregating around coastal areas looking for food.
"When the larvae turn into adults they feed off pollen," he said. "We think that this year a lack of flowers in the countryside means the flies are migrating in search of food.
"Some are going out to sea but after a while they get tired and fly back.
"This species is quite lethargic and so when they come back in they land straight away and suck up moisture off people's arms."
He said over the past few weeks the trust had received a number of calls from people alarmed at the large numbers of the flies because they resemble bees and wasps.
"They are totally harmless and in fact are very good for gardens because they pollinate and eat aphids," he said.
However, they have proved not to be so popular with holidaymakers and day-trippers.
"They are a nuisance but they do not sting, they just crawl all over you which can be annoying. They are attracted to people's brightly coloured T-shirts because they think it's a flower," Mr May explained.
He added that the hover flies will die off as the weather cools.