The December Moth

The December Moth, Poecilocampa populi, (Poecilo is Ancient Greek for ‘varied’ or ‘spotted’, campa meaning ‘field’ and populi meaning ‘common’) is a very aptly named moth, being one of the few, if not the only moth flying in the cold depths of winter.

Active when others are asleep

It is a medium sized moth, with a wingspan of about 3 to 4 cm and its flight time is from October to December, long after other species of moth have died off or gone into hibernation. In appearance it is very distinctive having charcoal grey wings with a prominent cream band across them, its head is a creamy colour too. The female is much larger than the male, with slightly transparent wings, having less scales on them than the males.

It is fairly common throughout the British isles wherever there is deciduous woodland, gardens and hedgerows, in the north of England it can be found in most places up to the tree lines on the edges of the uplands.

Night flying

Adult December moths are active only at night and are attracted to man-made light, so are very easy to trap and count, moth ‘trappers’ don’t actually trap the moths though, despite the name it’s just the term used for counting and identifying species and they are not harmed! There are many different ways of trapping them too, my preferred way is to simply hang a white sheet over a washing line and point a torch at it and see what lands on the sheet.

They have an peculiar habit of pretending to be dead if disturbed whilst resting in the day, they will simply drop to the ground and remain still. If they are disturbed further they then flap about moving their wings in a strange, slow, jerking way, when they are put somewhere safe to go back to sleep you can tell they have nodded off again as they will tuck their antennae under their wings!

Lifecycle

In winter the moth is in either its adult stage or in egg form, eggs are laid in winter on the underside of twigs and branches and the caterpillars hatch around April, feeding on the leaves of a wide variety of native deciduous tree and hedge species including Birch, Blackthorn, Oak and Hawthorm. Like the adults the caterpillars are nocturnal too, only feeding at night and resting during the day underneath branches.

In June or July the caterpillars will move down from the leaves of the tree they have been feeding on since spring to hide under bark or in leaf litter, this where they will pupate until hatching in early winter.

Antifreeze for blood

There are several methods the December moth has evolved to get an early start over other insect species and beat them to food plants like this. Compounds like alcohols in their blood act in a similar way to antifreeze and they can also warm themselves up by vibrating in order to fly on a cold night, if it’s freezing they may purge water from their system to avoid becoming frozen.

As they are active in the winter this means they cleverly avoid being hunted by bats like the Daubentons, which will be in hibernation. However their eggs are easily picked off by starving winter birds like flocks of Long-tailed Tits or Wrens as they forage in the hedges and woods so, as with everything else in nature, it appears that there is no easy way of beating everyone else in the race for food or avoiding being eaten oneself.

A B-H