Friday, 7 September 2012

Evolution works in mysterious ways

If Creationists wanted to cite an animal that seems to defy the theories of evolution, they should look no further than the common cranefly, Tipula paludosa.

Every year as summer fades into autumn a rag-tag invasion of daddy-longlegs stumbles into homes all over the country, crashing into lampshades, dangling helplessly from undusted cobwebs, and willfully drowning themselves in washing-up bowls and tea cups. So far this week I have rescued one from the empty bath, from which it seemed unable to escape despite intact wings, and watched one fight to the death against a window pane next to an open door.

It's the legs mainly. Why on earth do they have those ridiculous legs? Yes I've read the theories - they use them like cat's whiskers at night to make sure they don't bang into things, or as a tripod from which the female can lay her eggs in the turf, or even, like a lizard's tail, so that they can escape if caught in a spider's web. None seems to be very convincing, as surely the handicap those same legs seem to afford it outweigh any of these supposed benefits. And anyway they bang into things all the time.

Tipula paludosa, which translates loosely as 'boggy cranefly', actually begins life in the earth below our feet - in lawns, sports fields and agricultural grasslands. And its here that it seems far more at home. Its larvae - the leatherjacket - gnaws it way to adulthood via the roots of the grasses above. It's tough and hardy, unlike its kamikaze parents, and survives through the winter and into the next summer this way before emerging as an adult - if the starlings and rooks don't find it first with their probing, pointy beaks.

Yet daddy-longlegs are not without beauty. In the fields their transparent wings, with their dark, stained-glass patterns, reflect the autumn sun when they clamber among the tall grasses. And today in the drizzle I spotted one climbing slowly up a stalk with a glassy bead of rain on its back like a pearly, Art Nouveau brooch.

Despite their apparent shortcomings craneflies deserve our respect. They are one of the oldest and most diverse groups of flies - one in ten flies in the UK belongs to the group. They include the largest fly - Tipula maxima - in terms of wingspan, at 65mm, and some of the smallest, the 'bobbing' gnats. They provide an important food source both as larvae and adults for many birds. And who could fail to love a family that includes species called the hairy-eyed cranefly, and the gulper.

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