Leading article: Welcome home

Most people will be surprised to hear anything as exotic as a colony of scorpions has been quietly flourishing for some years now in a brick wall in Kent for years, causing no harm to anyone. It is equally little known that various snapping turtles, chipmunks, wallabies and even aardvarks have, somewhat improbably, decided that life under Britain's leaden grey skies, so far from home, is not as bad as they might originally have expected.

Is this a cause for alarm? To some people, yes. A new report says the very existence of such newcomers in the wild poses a threat to indigenous species.

The report has a point. The thoughtless introduction of grey squirrels to this country has had catastrophic consequences for the less competitive reds. It's been the same story with American crayfish and mink.

But we shouldn't develop a kind of squeamish horror about all foreign species. It seems absurd and illogical to talk up the virtues of controlled migration among humans and then anathematise the same phenomenon among birds and animals. In any case, many creatures we now think of as British were once foreigners, starting with rabbits and pheasants. Give the scorpions a chance. And that goes for the aardvarks.