Gut-sucking cannibals lead invasion of creepy-crawlies

The Sunday Times Published: 16 October 2011. Lois Rogers.

The movements of exotic animals, plants and insects into Britain from as far away as China could be a result of climate change

Britain has become home to a ferocious Mediterranean insect renowned for its savage lifestyle, which includes sucking the insides out of its prey.

Antlions are usually found in warmer regions of southern Europe, but they have been discovered at the Holkham National Nature Reserve in north Norfolk.

Their move northwards could be linked to changes in climate – a trend also noted with a form of ragweed whose pollen is one of the most allergenic from any plant and which has reached Europe from north America.

The European commission is to launch a £4m project to halt the spread of Ambrosia artemisiifolia, or annual ragweed, which has caused deaths in parts of Europe since its arrival.

There are fears that the plant, a form of ragweed that causes an allergic reaction to about a sixth of people exposed to it, could reach Britain in the next year or so.

While there had been reports of antlions in the sandy ground beneath the Holkham reserve´s pine woods since 2005, there was uncertainty about the exact species and numbers involved.

It was assumed they would soon be killed off by Britain´s inhospitable climate, but Michael Rooney, a senior manager at Natural England, which runs the Holkham reserve, said the opposite was actually happening: the colony was expanding. “This year we found no fewer than 1,905 larval pits, confirming not only that the colony was still present but had almost trebled in size,” he said.

Adult antlions resemble small dragonflies, but their name comes from the ferocious appearance and lifestyle of their larvae.

The creatures dig cone-shaped pits in loose sandy soil, meaning that any insect unfortunate enough to wander over the rim slides down the steeply angled, shifting sand. At the bottom, it is seized in the antlion´s huge jaws and its insides are sucked out.

The larvae live for two years, preying on ants, woodlice and other small invertebrates, before pupating into flying adults.

As adults, they live for less than a month, in part because after mating, the females fly to the ground to lay eggs where many are trapped and eaten by the larvae left by adults of previous generations.

The antlion is the latest in a number of ferocious small animals to colonise Britain. Some have spread naturally from Europe, while others have been inadvertently introduced by humans.

Invaders include the false black widow spider, which is now being discovered regularly in the south of England and the Isle of Wight, and the European yellow-tailed scorpion, with a colony established at Sheerness in Kent.

One of the most destructive newcomers is the so-called killer shrimp, a freshwater crustacean that grows up to 2in long. It consumes such a wide variety of insects and small fish that it can devastate the ecosystems of the lakes it invades.

Another is the Chinese mitten crab, which also lives in fresh water and was brought to Britain from Asia, probably in the ballast tanks of cargo ships. The mitten crab is capable of causing structural problems because it can burrow into fragile mud riverbanks, riddling them with holes until they collapse.