THE
FIGHTING
CATERPILLARS
OF
THE
ORANGE-TIP
BUTTERFLY W I L F R I D S . GEORGE
IN 1965, a female Orange-tip Butterfly (Anthocharis cardamines, L.) laid for me a few eggs, since when I have tried each year to keep these attractive insects through their life stages. Often I find their eggs or small larvae on the seeding flowers of the common Garlic Mustard (Alliaria officinalis) and take home the complete flower-stalks for Observation. T h e pale green eggs turn bright yellow in a day or two, then hatch about ten days after being laid. But I was soon aware in the first year that caterpillars were disappearing only a day or two after hatching. An inspection with a pocket lens showed two cases where a slightly larger Caterpillar was actually eating a smaller one. I thought that these larvae could not teil the difference between their food and their own brethren (who must surely smell and taste strongly of Garlic Mustard). I could not believe that there was any real vicious intent in these seemingly gentle creatures. All the same, it was clear that they must be separated. (In the wild, only one egg is laid on each flower-stalk). I saw to it from then on that each larva had its own sprig of food plant, each in its own bottle of water. So long as it had seed-pods available, it would not leave its sprig, but greedily nibbled and grew fast. I watched how the green caterpillars consumed the pods, and also the seeds themselves holding the latter and rotating them as they ate them, much as we would an apple. (I suspect that these seeds may still have been attached by invisible fibres to the plant). After some sixteen days and nights of almost continuous feeding, they left their food and pupated in secluded corners, where they remained for ten or eleven months. I find it surprising that whether outside in a cold shed or indoors in comparative warmth, the butterflies managed to time their emergence to coincide with their colleagues in the wild. But on 16th June, 1968, all was not well. A hungry 2 cm. long Caterpillar had eaten all his seed-pods in the night, and had crawled down, along, and up to the sprig of a slightly smaller colleague. I found the two larvae facing each other along a seed-pod, with their bodies arched menacingly and heads stretched forward well above the pod but only three or four millimetres apart. They were just perceptibly trembling. I had just time to call my wife and daughter over, when the battle commenced. It did not last long. Suddenly they lunged viciously at each other for several strokes, tili the longer apparently bit the shorter just behind the head, and the loser feil instantly to
CATERPILLARS OF THE ORANGE-TIP BUTTERFLY
213
my window-sill. I placed it carefully on another sprig, but noted that it had a small oozing injury on its right dorsal first segment behind the head. Later that day the victim changed its skin, (whether or not prematurely, I cannot teil), and then showed a black mark on its head in an anterior dorsal position, slightly to the right, (the new head, being larger than the old, is formed inside the first segment of the old skin). This Caterpillar then proceeded to feed normally, and to pupate to an unmarked chrysalis. I have kept it separately, but think it unlikely that the butterfly will bear any scars from its childhood fight.