Northern winter moth and winter moth
In late October, it seems impossible that one could encounter Lepidoptera. However, there are species that begin their active life as an imago only after the arrival of the first frosts. Northern winter moth and winter moth— representatives of the geometer moth (Geometridae) family, winter moth (Operophtera) genus—are such cold braving fellows.
The male moths of both species are rather modest in colour, i.e., grey and brownish beige, while their hind wings are lighter and nearly patternless. The wings are quite large (spread 2–3 cm) but seem very fragile and delicate. The females of both species are flightless and evolution has rendered their wings into tiny wing rudiments.
The larva of winter moths, who hatch from eggs laid in autumn, feed on young shoots and leaves in the crowns of deciduous trees.
Northern winter moth (Operophtera fagata) mainly feeds on the birch but does not shun other trees and shrubs either. In years of mass reproduction the larvae may eat the trees bare already in June. Quite extensive damage can be seen in birch stands from time to time. The trees usually grow new leaves again in the second half of the summer but the damage impedes tree growth and causes tree tops and branches to dry. The danger of mass reproduction is decreased by entomophagous birds since the larvae are active during the birds’ nesting period in spring. The moth is widespread on the territory of Estonia, as well as quite common. Male moths begin their mating flight in the early hours of the evening to find a flightless female who sits waiting somewhere on a tree trunk, and will climb to the tree crown to lay eggs after the mating. The males like to fly towards the light, where it is easy to view and photograph them. It takes more effort to find a female specimen.
Winter moth (Operophtera brumata) is polyphagous in the larva stage and prefers to feed on oaks, fruit trees and shrubs, as well as other deciduous trees. The males of the species fly in late autumn. Their flight commences after the first night frosts. The moth is common all over Estonia; one may encounter it from September to November, very rarely even in December, when the autumn has been warm. The flightless females climb on tree trunks, where the species mates, then ascend to the tree crowns to lay their eggs into bark crags, under lichen, etc. The larva feed on buds and young leaves in the spring. Individual trees can be protected from the damage done by the species with glue girdles placed on the trunks in late September; these stop the flightless females from climbing to the crown to lay eggs. This also helps to estimate the population size of winter moths. The flying males, on the other hand, like to head towards the light—you may admire the splendid flight of moths around a lamp illuminating your home garden in the autumn evenings and reminisce about the summer past.
Allan Selin
