There are 14 species of green lacewing and 29 species of brown lacewing in the UK, but only one of them spends the winter as an adult insect. It goes by the name of Chrysoperla carnea, and it very often sneaks into houses in an effort to escape the cold outdoor temperatures.
Once inside a strange reaction occurs. Their bodies change colour from bright green to pink! This isn't a sudden colour change, like say a chameleon. It takes a few days, but it is a total change. Even the veins on their wings turn pink.
Why this happens is a bit of a mystery. I've been told that it's the result of the cooler autumn temperatures and reduced hours of daylight. But if this is the case then why does it still happen inside heated buildings with electric lighting?
Another theory is that it's a camouflage thing to blend in with the autumn foliage colours, but again inside houses this is a bit useless. Perhaps it's just a genetic-body-clock-thingamabob (stop me if I'm getting too technical) because when mating time comes around in spring they change back to green again.
Al good gardeners know that lacewings are valuable insects to have around as their larvae spend all day eating aphids. So if you are lucky enough to have any Lacewings staying with you this winter be sure to look after them. :)