The median wasp is a nastier species than the other varieties buzzing round the patios and picnics of late summer Britain. It is bigger, more aggressive and more persistent in stinging. Since it often nests in bushes rather than roof spaces, gardeners and pets are more likely to infuriate them. "I would definitely say they are more unpleasant," said Chris Turner, a senior manager with a pest-control company.
The median is just one of dozens of insect species on the move in Britain thanks to warmer summers. First found just outside Brighton, East Sussex, in 1988, it has now reached Wales, Cornwall and Yorkshire. In the last 10 years eight summers (officially from 1 June 1 to 31 August) have been warmer than average. This year's was just over a degree above the 15.4C average for central England between 1961 to 1990.
The bee wolf has also begun a swift move northwards. It is a big wasp which paralyses honey bees with its sting and flies back to its burrow carrying its victim. The bee is then eaten alive by the growing grubs. Until the early Eighties, it was known only on the Isle of Wight and in a couple of places in Essex. But since then it has been heading north at 30 miles a year, and has passed Spurn Head, Humber-side.
Britain's native hornet, double the size of an ordinary wasp, has also been moving rapidly upcountry. "It's having a very good time," entomologist Mike Edwards said. "It's quite docile. You'd have to really provoke it to make it sting you, but when it does it's quite a whack."
Similar findings are being made for dragonflies, butterflies, moths, crickets and even cockroaches. Sometimes it is a case of a long-established native species abruptly expanding its range northwards, turning up in places where it has not been seen for many decades - or never before.
The yellow-winged darter is a dragonfly from Europe's deep south which crossed the Channel in its thousands in the very hot summer of 1995. It has now bred for two summers in succession at a few sites in Norfolk.
Changes in woodland management and habitat creation may explain some of these dramatic changes, but scientists agree that warmer weather is the major factor.
Martin Warren, of Butterfly Conservation, said: "A tiny difference in average temperatures makes a big difference to an insect's chances of survival. This is a real movement of species, there's no doubt about it, and it is very suggestive of global warming."
There will be losers as well as gainers. Species such as the Scotch burnet moth which love the cold may be forced out of northern Britain and ousted from its mountain tops.
Northern exposure: The long winged, cone head bush cricket (1), Roessel's bush cricket (2) and the orange tip (3), ringlet (4), gatekeeper (5), small skipper (6) and holly blue (7) butterflies and the red underwing moth (8) are all spreading, mostly northwards. The map butterfly (9) has not yet arrived from Europe but is expected soon. Among the dragonflies, the yellow winged darter (10) may have established a breeding population, the migrant hawker (11) is spreading east and north while the large, rare lesser emperor (12) may become more common. The unarmed stick-insect (13) introduced from New Zealand, is spreading in Cornwall. Also expanding are the hornet (14) and median wasp (15) Photomontage: Mark Hayman