As moths rely on external sources of heat to warm their bodies, these chilly winter months mean most Lepidoptera are forced to remain inactive. As always there are a few exceptions to the rule, however. The December Moth is a rather amply named example that flies late into Winter.
This species is one of the few moths you might see over the holiday period. They are able to withstand colder temperatures due to their fluffy ‘mane’. Their bodies are thicker and covered in long hair-like scales that provide insulation and keep the moth warmer, so its muscles work as efficiently as if it had been a summer-flying species.
Why might they go to the trouble of being thicker and hairier than other species? Well, it may be that they do this so they can avoid predators such as bats, which tend not to feed in the coldest months.
The species that fly in autumn and winter mostly lay eggs on woody parts of a variety of trees and shrubs. The caterpillars won't hatch out until early spring when the first tree buds burst into leaf. The emergence of the caterpillars is of vital importance to the success of insect-eating birds like Blue Tits and Great Tits. These birds have evolved to synchronise their breeding with the peak emergence of caterpillars so there will be plenty of food to raise their broods. It can take 100 caterpillars a day for one Blue Tit chick, so getting the timing right is crucial!
The December moth is commonly found in woodland but also frequents scrub, hedgerows, and established gardens. The adult moths are incapable of feeding, but their caterpillars enjoy broadleaved trees including oaks, birches, elms, hawthorns, Blackthorn (Prunus spinosa), poplars and sallows.