In the days when I used to run a moth trap regularly, I can’t recall a night when I didn’t catch something. Even in the dead of winter, a wide selection of moths is on the wing on all but the chilliest of evenings. But don’t take my word for it: despite lockdown you can confirm this for yourself, and without the need to run a moth trap. If you have a reasonably bright outside light, leave it on overnight and you will find moths in the vicinity the following morning, sitting on the wall and on nearby surfaces. That’s assuming the local Robins don’t discover this food supply.

You may wonder why on earth a moth would evolve to be on the wing in the middle of winter. Who knows for sure, but a couple of suggestions spring to mind. Firstly, it might be a case of getting ahead of the game: by mating and laying eggs before leaves are even in the fully-formed bud stage, larval emergence can be timed to coincide with the freshest and juiciest young foliage as it appears. Another possible advantage is that there are fewer mammalian and avian predators around at that time of year. However, if this is the strategy then it’s not entirely successful: on mild nights the occasional pipistrelle will wake from slumber to snack on adult moths and birds such as Goldcrests somehow find the moths’ eggs in the daytime.

Whatever the reason, plenty of moth species do just appear in winter. Their eggs hatch in spring and the resulting caterpillars are so important as a food source that birds such as Blue Tits and Great Tits align their nesting so their hungry chicks hatch when the larval biomass is at its peak.

Above: December Moth Poecilocampa populi
This attractive moth has a wingspan of 30-45mm. The forewings are greyish-brown with yellow markings and reddish-brown margins, and the thorax is ‘fluffy’ and pale at front. It flies from October to January and is common except in the north. Its larvae feed on various deciduous trees.

Flightless Females – An interesting feature of some species of moth that emerge in winter is that females have vestigial wings and hence are flightless. Having emerged from the pupa, they climb up trunks and branches, and emit pheromones (chemical attractants) to lure a mate, thereafter laying eggs in crevices in tree bark. For those with a garden and an adventurous streak, try venturing out after dark with a torch and you will be surprised what you find. Here we see a newly-emerged flightless female Winter Moth mating with a winged male, on the branch of a garden plum tree. ©Paul Sterry/Nature Photographers Ltd

Above: Winter Moth Operophtera brumata
Males have grey-buff forewings with subtly darker cross bands, and a wingspan of 24-28mm. They fly from November to February and are commonest in southern Britain. The larvae feed on various native trees and shrubs. ©Paul Sterry/Nature Photographers Ltd

Above: Northern Winter Moth Operophtera fagata
This species is similar to the Winter Moth but marginally larger (wingspan 32-40mm) and paler, with a slightly earlier flight period, usually October to December. The larvae feed on birches and other trees and shrubs. It is commonest in the north.
©Paul Sterry/Nature Photographers Ltd

Above: March Moth Alsophila aescularia
Males have narrow, grey brown forewings that overlap one another at rest; the wingspan is 25-35mm. The species appears from February to April and is common except in the north. The larvae feed on deciduous trees and shrubs
. ©Paul Sterry/Nature Photographers Ltd

Above: Pale Brindled Beauty Phigalia pilosaria
Males are typically pale yellow-buff with a grey wash and dark speckling; dark forms do occur. The wingspan is 35-40mm and the moth flies from January to March. It is widespread but scarce in the north, and the larvae feed on deciduous trees.
©Paul Sterry/Nature Photographers Ltd

Above: Oak Beauty Biston strataria
Both sexes of this attractive moth can fly, their dark-speckled white wings having 2 broad, black-edge reddish-brown cross bands; the wingspan is 40-50mm. Only males have feathered antennae. The species flies from February to April and the larvae feed on deciduous trees. The species is commonest in southern Britain
. ©Paul Sterry/Nature Photographers Ltd

Above: Spring Usher Agriopis leucophaearia
A typical male has reddish-brown forewings with a broad, white central band; the wingspan is 32-36mm. The moth appears in February and March and its larvae feed on oaks. It is commonest in southern Britain
. ©Paul Sterry/Nature Photographers Ltd

Above: Dotted Border Agriopis marginaria
A typical male has dull orange-buff forewings with dark speckling, and a row of black marginal dots; the wingspan is 28-32mm. It flies from February to April and its larvae feed on deciduous trees and shrubs. It is commonest in southern Britain. ©Paul Sterry/Nature Photographers Ltd

Above: Mottled Umber Erannis defoliaria
The male is variable but a typical form has reddish-brown cross bands on the forewing enclosing a broad paler central band containing a dark spot; the wingspan is 30-40mm. It flies in November and December and its larvae feed on deciduous trees and shrubs. It is commonest in the south. ©Paul Sterry/Nature Photographers Ltd

Above: Early Moth Theria primaria
The male’s narrow wings overlap one another at rest and are buffish-brown with a darker central cross band; the wingspan is 34-36mm. The moth flies in January and February and the larvae feed on Hawthorn and Blackthorn. It is common except in the north. ©Paul Sterry/Nature Photographers Ltd

Hibernation – Interestingly, another group of moths emerges in the autumn and hibernates through the worst of the cold weather, reappearing again in spring. However, during mild winter spells they sometimes emerge and appear at lights. Hibernation sites include garden sheds and cosy tree holes.

Above: The Herald Scoliopteryx libatrix (left) is a widespread and distinctive moth has forewings with indented, ragged margins and a hooked tip; they are a mix of grey-brown, marked with white crosslines and veins, and intense orange-red patches; the wingspan is 40-45mm. It appears from September to November and again after hibernation in April and May. The larvae feed on willows and poplars. The Chestnut Conistra vaccinii (right) is a widespread moth has reddish brown forewings dusted with blue-grey scales and jagged cross-lines; the wingspan is 30-34mm. It flies from September to April, hibernating in cold weather. The larvae feed on deciduous trees. ©Paul Sterry/Nature Photographers Ltd

Above: This December Moth larva, photographed in spring, is hard to spot but if discovered makes a juicy meal for a hungry bird. ©Paul Sterry/Nature Photographers Ltd

Above: Most moths that appear as adults in winter go on to pupate in the soil or near the surface. This may give them protection from most predators, but not the fungus Isaria (Paecilomyces) farinosus. Its mycelium invades pupae, digests them alive and then reproduces by producing spores borne on a stalk that projects just above ground level. ©Paul Sterry/Nature Photographers Ltd