Caterpillar rescue

The Cairns Birdwing, Ornithoptera priamus euphorion (formerly Troides euphorion), is our biggest and one of our most spectacular butterflies (female, male) and it is one of the few that we actively encourage in our garden. The adults only need nectar and they aren’t very fussy about which flowers they feed on, but their caterpillars only eat one plant, the Aristolochia vine, so our encouragement takes the form of planting the vine.

From five weeks ago until last week we had a semi-resident female attended by a couple of males, and she was laying eggs as though she was going to repopulate the whole suburb, if not the whole city. That’s great, we thought, as she flitted from one creeper to another … and then they all started hatching.

spiky black caterpillar
Just hatched: the young caterpillars, about 5 – 10 mm long, have branching spines

And eating.

spiny caterpillar
Halfway to maturity: about 25mm long, and the spines are now smooth but more colourful

We don’t mind the caterpillars eating the creeper – that’s what it’s there for – but their appetites are enormous because they have to grow to the size of my middle finger before they are ready to pupate, and before long we could see that they were in trouble: our vines were not big enough to feed them all and they were likely to starve before they matured.

What to do? We moved a couple of caterpillars to a young vine that their mum hadn’t noticed … but then watched in dismay as a bigger vine wilted and died; picked caterpillars  off the dying leaves and moved them to another vine; watched that vine shrink by the hour under a double load of ever-larger munchers; asked neighbours if they had vines (no luck); gave some caterpillars to a friendly school-child whose (enlightened) school had vines; gave some more to a friend whose friends had vines; and hoped that the remaining leaves would last our remaining caterpillars until they pupated.

So far, so good: one pupa that we know of (there may be one or two more) hanging on the one surviving vine, two more caterpillars which are so big they must be ready to follow suit, and still half a dozen leaves for them to eat. Phew!

But if their mum comes back, we will have to lock her away from her boyfriends. Enough is enough, okay?

7 thoughts on “Caterpillar rescue”

  1. We are having trouble with the green tree ants attacking the caterpilars and the pupa. I am now about to cut down as many of the green tree ants nest I can reach. Any advice on the interaction of the Cairns Birdwing caterpila and pupa with the green tree ants?

    Regards.

    1. Hi, Dave,
      As far as I know, the green tree ants will attack birdwing caterpillars and invariably win; I don’t know whether they also attack pupae. The only control strategies have to involve keeping the green ants away from the Aristolochia vine, either by wiping out the colony or (I guess) a physical barrier like mosquito netting. Bear in mind that each green ant colony builds multiple nests, most of them occupied only by workers, so you may have to destroy quite a few nests.
      It’s a pity in a way because the green ants are effective bio-control agents in keeping down pest insects on fruit trees, etc, but we can’t usually have it both ways. One compromise we maintained for some years in my garden was to kill off the green ants on the North and East edges of the garden, where the Aristolochia were growing, but leave them alone elsewhere. Perhaps something like that will work for you?

  2. Hi just wanted to know when what time of year do bird wig butterflies lay eggs and also what time do the caterpillars make cocoons. Is there any spots I could photograph them in the wild that are well know for there abundance?

    Thanks

    1. Hi, Rich,
      The seasonal pattern isn’t very strong – we seem to have adults all year – but the period just after the Wet season (say April – June) is usually best for adult numbers, with mating and egg-laying, and there’s a quieter period from about now until the beginning of the Wet. I can’t help much with where to look. Wet tropics rainforest is good but if I wanted the best chance of seeing them I would head for botanical gardens or wildlife sanctuary, where the management will have planted the butterflies’ food plant.

  3. Hi Malcolm,
    We only have two caterpillars (thankfully!) and we’ve just planted two more vines to keep up with their appetites. They are both about 2.5 inches long (maybe a bit bigger) and I’m wondering how much longer before they pupate? Can you give any advice? I don’t want them to starve!

    1. Hi, Tara,
      Two and a half inches is close to fully grown, so they should pupate in the next week or so. They normally drop off the vine and find another plant to pupate on, so don’t panic if you lose track of them.
      Good luck!

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