The Orange tip, like the primrose and the cuckoo, is a true herald of spring. It is one of the very few species that are on the increase in Britain, having spread northwards in recent decades, whilst still remaining widespread and abundant in the south.

Orange tips usually begin to emerge in mid April, but can appear as early as the end of March if the spring is exceptionally warm. The peak flight season for both sexes is early May. By the end of May the males have disappeared and just a few females remain. In Europe the flight season is longer, with the butterflies still on the wing in early July at moderate altitudes in the Alps.

Weather conditions during the flight season have a great affect on butterfly abundance the following year. In early seasons a high percentage of eggs are laid on cuckoo flower Cardamine pratensis but in late seasons the majority are laid on garlic mustard Alliaria petiolata. Larval survival is higher on garlic mustard, probably because it produces larger and more profuse seed pods and leaves for the larvae to eat. Hence in a late season tends to result in higher numbers of adults the following year.

Anthocharis cardamines - the egg on the right is freshly laid, that on the left is about 3 days old.

Although cuckoo flower and garlic mustard are the primary larval foodplants, females occasionally oviposit on charlock, hedge mustard or watercress; but regardless of the plant chosen, the eggs are always laid singly, and always in the same position - on the flower stalks. Sometimes more than one egg can be found per plant, but this is unusual, as the butterflies seem able to detect the presence of eggs that have already been laid. The eggs are skittle-shaped and greenish-white in colour when first laid, but turn to orange after a day or two, and then finally to grey.

Orange tip Anthocharis cardamines Stansted Forest, Sussex © Adrian Hoskins

Anthocharis cardamines, pupa ( normal form ) on garlic mustard stem © Adrian Hoskins

Anthocharis cardamines, pupa ( green form ) on garlic mustard stem © Adrian Hoskins

Male Orange tips begin emerging in early April, followed about a week later by the females. As with most butterfly species, female Orange tips must mate within a couple of days of emergence, after which they lose their attraction to the males. The staggered emergence is nature's way of ensuring that there are plenty of males available when the females emerge.

When seen in flight, female Orange tips can be difficult to distinguish from Green-veined Whites, but when they settle, the beautiful mottled green markings on the underside hindwings make them easy to identify. The green colour is actually an illusion caused by a mottling of black and yellow scales. The markings are an extremely effective camouflage which works against a variety of backgrounds - the butterflies are equally difficult to spot when at rest on bracken fronds, hazel leaves, or nettles; or on the white flowers of garlic mustard or umbellifers.

Orange tips visit a wide variety of wild flowers including bluebell, bugle, wood anemone, blackthorn, primrose, ground ivy, celandine, hawthorn, garlic mustard, early purple orchid, common vetch, dog violet, colt's foot, dandelion and cuckoo flower.

When nectaring or settling for short periods, they normally keep their wings half open. This has the effect of trapping a tiny pocket of warm air over the thorax, which aids rapid body warming. In hazy weather or late evening sunshine however Orange tips often bask for long periods with the wings fully outspread.