When the weather turns cold, you may wonder what happens to these insects. Winter poses a problem for butterflies as they cannot get warm enough to become active. They enter a dormant phase either as an egg, larva, pupa or adult insect, dependent upon species. This isn’t simply a random choice but is a way of ensuring that the insect’s awakening the following year corresponds with the peak availability of its main food source. Amazingly the Painted Lady avoids winter conditions completely by migrating long distances to regions in North Africa and the Middle East.
Eggs, larvae and pupae tend to be hidden away, though you may find Large White pupae attached to the walls of your house. Those species that overwinter as dormant adults include Brimstone, Small Tortoiseshell, Peacock and Comma. The Red Admiral, which has become a common sight in British winters of late, doesn’t enter a proper dormancy but can become active on any suitable sunny days.
The Comma has its name written on the underside in the only white marking, which resembles a comma. When resting with wings closed this butterfly has excellent camouflage, the jagged outline of the wings giving the appearance of a withered leaf, making the butterfly inconspicuous when resting on a tree trunk or when dormant in winter.
The sea urchin-shaped eggs of the Brown Hairstreak are laid singly on the bark of blackthorn, typically on one- or two-year old growth that is in a sheltered area exposed to the sun. Within the 1mm pin-head sized egg, the larva partially develops before entering hibernation for the winter. Overwintering eggs are particularly vulnerable to hedge-trimming since they are laid on the youngest growth of the foodplant.
The Orange Tip pupa (or chrysalis) is formed on an upright plant stem that provides a suitable overwintering site, attached by a silk thread girdle. Green when first formed, the pupa turns light brown to more-closely match its surroundings. Several crucifers are used as foodplants, especially Cuckooflower in damp meadows and Garlic Mustard along road verges. It also lays its eggs on Honesty and Sweet Rocket in gardens. The chrysalis will not survive winter if the plant stems are cut down before the adult butterfly emerges in spring. Leaving part of your garden naturally unkempt helps to benefit other wildlife aswell.