Bird feeders

Posted by Graeme Lyons , Saturday 18 December 2010 12:17

This boring little moth is a male Winter Moth. How can you tell it's a male? Well, the females are completely flightless and belong to a small group of geometrids that have flightless females. They all fly in late autumn,  winter or very early spring. I think it's a fascinating tactic. There is so little energy available in the winter, the moths have to live off energy acquired as a larvae. This is not enough energy for the females to produce eggs and fly so the females have given up flying. Watch out for the Northern Winter Moth too, it looks very similar but is bigger and paler and is coming to the end of its flight season now.
But the remarkable story of the Winter Moth (and the whole suite of winter geometrids with flightless females) does not stop there. They are all larvae, pretty much at the same time around May and they are all more or less (with the exception of a couple of scarce ones) woodland species. I assume that woodland provides a slightly more stable and warmer microclimate for them to sit out the really horrible nights in the winter but it could also be  that the females require structure to crawl up to await the arrival of the males. Along with Mottled and Scarce Umbers, in May, the frass from all these individual caterpillars is actually audible as it lands on the previous year's carpet of dry leaves. This small number of incredibly specialised (but also incredibly abundant) moths, must play a huge part in the fledging success of woodland passerines. So spare a thought for our humble winter moths this Christmas, without them, our woodland birds would be buggered!

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