Male Orange-tip Butterfly (Anthocharis cardamines) - Wye Valley, UK.
Canon 300mm F2.8 IS plus 2 x Extender and Canon Extension Tube EF 25 II
Fill Flash -3, Tripod
AV Mode, Evaluative Metering dialed to -1
Text adapted from - http://www.ukbutterflies.co.uk/species.php?vernacular_name=Orange-Tip
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 common and fairly abundant in the south.
The bright orange tips to the males' forewings (the females lack the orange) are believed to be aposematic, acting as a warning to birds that the butterflies contain toxins derived from the larval foodplants. It is notable that many other butterfly species also have very brightly coloured males, but plain females. One reason for this is that males are far more active, constantly flying in search of mates, and in constant danger of being attacked, so they need to advertise their toxic nature. Another reason is that they need to advertise their presence to potential mates. Females on the other hand are generally passive, tending to move very little until mated. When searching for egg-laying sites they tend to move slowly and deliberately, and for them, plain colours or good camouflage are a better means of defence.
The main foodplants are Cuckooflower (Cardamine pratensis) and Garlic Mustard (Alliaria petiolata). Charlock (Sinapis arvensis), Hairy Rock-cress (Arabis hirsuta), Hedge Mustard (Sisymbrium officinale), Large Bitter-cress (Cardamine amara), Turnip (Brassica rapa) and Winter-cress (Barbarea vulgaris) are also used.
Orange-tip larvae are noted for their cannibalistic tendencies - this has probably evolved because most of the larval foodplants (e.g. cuckoo flower) only produce enough foliage to sustain a single larva through to full development. Larvae will not leave the plants on which they hatch, so for their own survival it becomes necessary for them to devour their competing brethren.
The slender green larvae feed nocturnally on the leaves of the plants, but in the daytime habitually rest on the seedpods, where they are superbly camouflaged.
Caterpillars which have been feeding on cuckoo flower always leave the plants when ready to pupate, and attach themselves with a silken girdle to a nearby woody stem. Caterpillars on garlic mustard, however, often pupate on the stems of the plant on which they fed. The very distinctive pupa cannot be mistaken for any other species. There are two colour forms of the pupa - green, and brown, of which the brown form is by far the commoner.
Male Orange-tips begin emerging in early April, followed about a week later by the females. As with many other butterfly species, female Orange-tips must mate within a couple of days of emergence, after which they appear to lose their attraction to the males, so the staggered emergence is nature's way of ensuring that there are plenty of males available when the females emerge.
There is virtually no variation in the colouring or patterning of Orange-tips, but there is a great deal of variation in size. The smaller butterflies may result from larvae that have fed on cuckoo flower - these plants have barely enough foliage to sustain the larvae, and it is possible that they literally run out of food, and pupate early.
When seen in flight, female Orange-tips are extremely difficult to distinguish from Green-veined Whites, but when they settle, the beautiful mottled green markings on the underside hindwings make identification easy. The colour is not caused by green pigment, which is rare amongst butterflies, but is an optical 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 very difficult to spot at rest on the bracken fronds, hazel leaves, nettles, and garlic mustard flowers on which they roost on dull days.
Orange-tips visit a wide variety of flowers including bluebell, bugle, wood anemone, blackthorn, primrose, hawthorn, garlic mustard, violets and dandelion, but have a particular fondness for the nectar of cuckoo flower. When nectaring, or settling for short periods, they normally keep their wings half open, but in hazy weather or late evening sunshine will bask for long periods with the wings wide open.