Just as the last flying ants collapse, exhausted, after their spectacular aerial mating swarms, Britain's modest heatwave has brought a new insect plague to parts of the south and east coasts.
Millions of marmalade hoverflies have crossed from the continent on warm thermals, causing havoc on beaches and seafronts where children and families have mistaken their banded black-and-yellow colouring for wasps.
"It was just horrific," said esplanade shopkeeper Jeanette King, a former mayor of Walton on the Naze in Essex where the "marmalades" - harmless and the commonest of Britain's 270 species of hoverfly - came ashore at the weekend.
"Children were screaming, people were covering up prams and pushchairs. If you stopped still for a moment, you could get covered in them. I was told that it was the same all the way to Kirby le Soken, and that's quite a step [away]." Drifts of the hoverflies also piled up along the foreshore between Walton and Clacton, as insects which had failed to make the Channel crossing were washed up by the tide.
"Unfortunately that's one of the sights laid on by the insect world when there's a big migration like this," said Austin Brackenbury, whose hoverfly records compiled at a railway signal box near Sheffield are part of one of the biggest and most thorough databases devoted to any British insect.
"The hoverfly is completely benign and a very important pollinator. It only visits flowers and honeydew and its larva do a great job of keeping aphids down."
Named after thick-cut marmalade, which its banding resembles, the commonest hoverfly - like its relatives - cannot harm anyone, let alone a fly. Mr Brackenbury said: "Its mouth parts are designed for mopping-up; there's no way it could bite. It doesn't have a sting and it won't give you itches or anything like that.
"People would do better to keep an eye out for 'white-faced wasps' - the ordinary variety which end up with white faces exactly like clowns, because they get covered with pollen from willowherb and the like."
Telling the hoverflies from the wasps is a problem, however, according to Roger Morris of English Nature, one of the country's leading experts on the insects - officially the Syrphidae sub-family of Diptera, or flies. He said: "The wasp-like colouring is a defence against predators like birds and it is extremely successful. So in Britain in the summer, you are much more likely to meet a hoverfly than a wasp."
The main difference is invisible to the lay observer, given that most encounters happen when the wasp or fly is airborne: wasps have four wings, hoverflies two. More obviously, wasps are "wasp- waisted" while the hoverfly's thorax and abdomen are divided by less of a narrowed section or have none at all.
"Both insects have a whine unfortunately," said Mr Morris, "but hoverflies are less aggressive than wasps. They are also less inclined to come to sweet things [the bane of a picnic will probably be a wasp]."
Hoverflies are also, not surprisingly, more skilled at hovering and do it - along with flying sideways - more than wasps. Mass migrations happen every four to five years in Britain, usually when favourable weather coincides with a rise in the aphid population here and in Europe.
Mike Solomon, another hoverfly expert based at East Malling horticultural research centre in Kent, said: "They're something to welcome, even if large numbers of any insect can initially be alarming. I'm afraid that anything flying which looks black and yellow gets a bad press, but hoverflies definitely don't deserve it."
The common wasp
Vespula vulgaris
· Named by Linnaeus 1758 but known since the first sting
· Lives in nests of 5,000 or so but has never mastered the winter food storage methods of the honeybee. Colonies collapse in autumn through cold. Only young fertilised female queens survive winter, emerging in April
· Distinctive pattern: black bands alternate with yellow, which each have two spots. The yellow face, framed by "bull's horn" antennae, has a distinctive yellow anchor mark. Four wings produce trademark whine. Sting in tail
· Flies by day, foraging for larvae, insects, scraps of meat etc. Lives colony life much like bees.
· Sting not usually severe but can cause anaphylactic shock which can be fatal
The marmalade hoverfly
Episyrphus balteatus
· Named in 1776 by the Swedish Baron Carl de Geer, who identified hundreds of insects
· Scores maximum points for environmental behaviour: flies are exceptional pollinators, and the larvae a very effective predator of aphids. They also eat decayed matter, freeing minerals for use by plants
· Flies live as individuals, laying eggs in aphid colonies
· Black and yellow or orange- banded, but unlike wasps have only two wings and no waist
· They fly only by day, and not in intense heat. Like garden plants. Live only for a maximum of a few weeks, and have many predators, but breed freely and produce repeated generations throughout the summer. Britain has 270 species
