This Summer is drawing to its stormy conclusion. As the temperature continues to drop and the daylight hours shorten, you have probably noticed decreasing numbers of butterflies on the wing. Without getting too depressed, the winter months will soon lie ahead of us and butterflies will disappear altogether. How does such a delicate and warmth-loving insect survive frosts, sub-zero temperatures, storms and anything else the coming months can throw at us?
Different species of butterfly employ different winter survival tactics so that when the weather improves again the following spring, they are ready to re-emerge and continue the survival of the species. Many butterflies spend the winter hibernating in the larval stage. The Meadow Brown, one of the commonest butterflies in our area, uses this strategy. The caterpillars hatch from their eggs in late summer and begin feeding on the various species of grass which make up their foodplants. As the temperature drops, the caterpillars go into hibernation low down in the grass. On warmer winter days the larva may stir and feed a little usually at night and then return to its hibernation. The following Spring the larvae become fully active, feeding and growing rapidly until they pupate finally to emerge as the adult insect a month later usually around late June. Altogether this butterfly spends about nine months of its life as a caterpillar. Common butterflies which follow this life cycle are other grassland butterflies; the Marbled White, Gatekeeper and Ringlet, as well as many other species.
One butterfly which hibernates overwinter as an adult insect is the Brimstone. This vivid yellow butterfly is one of the first seen in Spring and can be seen as early as February on warm days. It hibernates often by sheltering in ivy and so it is no coincidence that the butterfly looks like a leaf when at rest due to the distinctive shape of its wings. Other butterflies which hibernate as adults are Peacocks, Small Tortoiseshells and Commas. These insects often find spaces in the eves or roofs of outbuildings where they spend their winter months.
Another Spring butterfly, the Orange Tip, spends its winter as a well-camouflaged pupa. The adult insect emerges usually in April as the temperature rises and length of day increases. Finally, a butterfly that spends its winter as an egg is the rarely seen but reasonably common Purple Hairstreak. These butterflies spend all their lives in oak trees where the caterpillars feed on the leaves in the Spring. They then pupate and in midsummer the adults emerge, spending nearly all of their time in the oak canopy, occasionally coming down to feed from bramble flowers.
Naturally, winter takes its toll on all creatures because of the cold, predators and the increasing frequency of extreme weather events such as floods and unseasonable warm, wet or dry spells. It is remarkable that whatever stage of its life cycle each species of butterfly spends its winter months, it survives to take to the air the following year and become again one of the signs of summer.