Two years to the day since this post we have the same problem: we have so many Cairns Birdwing caterpillars (Troides euphorion) that they are eating themselves to a famine. We let an Aristolochia vine wind its way up one of our downpipes. Here it is, under stress five days ago and almost a bare stem this morning:
I have to congratulate the caterpillars on their economical eating habits – very little of the creeper is wasted – but wonder if they would blame their mum for laying too many eggs on one vine.
In the last two years we have signed up one of our neighbours to the caterpillar rescue team by giving her lots of Aristolochia seedlings. She now has several thriving vines in her garden and I have to say I was surprised to learn that the butterflies had not found them. Are they as finely tuned to their emergence location as turtles are to their hatching beaches? It’s hard to believe but really, our neighbour’s vines are only 50 metres from ours.
She is likely to have some next year, whether or not that’s the reason she hasn’t had any yet, since we have just carried half a dozen hungry caterpillars over to her.
My final photo here shows what happens when one of these caterpillars is frightened or provoked: it sticks out a pair of bright orange horns from the upper part of its head. The organ is called an osmetrium and, as wikipedia says, it emits a ‘foul, disagreeable odour’ which repels some of its potential predators.