We’ve had lots of Cairns Birdwing (Troides euphorion) butterflies in our garden in the last few weeks. Every time we go outdoors we are likely to see an enormous black and yellow female or one or two of the vivid green and black, only slightly smaller, males (photos here).
And we are re-running our caterpillar-feeding problem, since our Aristolochia vines haven’t recovered from the last feeding frenzy. We have been moving the caterpillars where we can but today I saw a well-grown individual resting quietly on a rambling rose that it had nibbled for want of anything better, and I couldn’t see any more Aristolochia to move it to. I suspect its outlook there is poor but on the other hand it may be ready to pupate.
They don’t pupate on the vine but on nearby vegetation. The one above is in a bottlebrush tree which supports a vine, so it may have crawled down and or it may have made its way across from elsewhere. In any event, it is hanging just above knee height and it’s doing fine so far.
This is kind of embarrassing but in a good way: sustained examination of the bottlebrush and the rose next to it reveals that we have about ten birdwing chrysalises, not just one or two. The lethargic caterpillar on the rose leaf has begun to pupate by making itself a silken sling like the one you can see above. (That is all it has done today, which seems like very slow progress.) We still also have large, active caterpillars – at least two on the vine in the bottlebrush.
The duration of pupation has been recorded as 26 days, according to Braby’s authoritative Butterflies of Australia, so we should be seeing them emerge around the end of this month.
Clearwing Swallowtails, Cressida cressida, lay their eggs on five different species of Aristolochia, according to Don Herbison-Evans and Stella Crossley’s great Butterflies of Australia site. Peter Valentine (Butterflies of the Townsville Area) agrees, adding that they especially patronise “the low small species scattered through the grasslands.”
The caterpillars change colour and pattern as they grow. The three below are all Clearwing caterpillars, at early, middle and late stages of development.
Cairns Birdwing caterpillars (Troides euphorion) also depend on Aristolochia – four native species of it, in fact. However, there is only one species that both kinds of caterpillars like: Aristolochia tagala.
Here for comparison are Birdwing caterpillars, showing young and old since they also change considerably as they grow:
Recently we have had both species of butterfly laying eggs on our vines and we can’t grow enough of them to feed all the caterpillars that hatch. It’s a continuation, really, of the situation we had back in May. Part of the problem is that a single caterpillar can consume a whole vine seedling within a day so we have difficulty rearing a vine past its infancy; we may have to begin growing them under wire mesh until they are well established.
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.
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?
We usually think of butterflies as fresh, bright, beautiful and short-lived (which I guess is why they are never ‘old’ in our minds) but that is not entirely true. Most of them certainly live for more than a day or two and many of them live for months. Wikipedia tells us that some species live for nearly a year and migrate surprisingly long distances – up to 5000 km. It makes sense, then, that we can see signs of ageing in our lepidopterous visitors.
The lady in my photo above turned up in our garden last week and shows plentiful signs of small accidental collisions and injuries. The edges of her wings are tattered, and she has lost many of the coloured scales from her wings. She is still impressive, however, with her 150mm wingspan and strong flight.
Cairns Birdwings lay eggs in our garden and they hatch, grow into large caterpillars, pupate and (sometimes) emerge as fresh, bright and beautiful adults. But a lot of our adults arrive from points unknown in quite battered condition. Braby’s monumental Butterflies of Australia says that some Australian swallowtails are migratory but suggests that movements of many others are dictated by seasonal changes in food supplies and can’t tell us whether or not our Birdwings are migratory. My guess, for what it’s worth, is that they could be loosely following the monsoon from North to South and back again as our Wet season develops and retreats. If so, our old lady above may be a Cairns Birdwing by birth as well as by name.
A tangled mess of creepers sprawls untidily near our front gate, supported by the tall stump of a grevillea and a couple of nearly-dead frangipanis. It is really not very attractive but we leave it alone for the Aristolochia vine which threads through the Golden Orchids, Gloriosa and other creepers.
What’s so important about Aristolochia? Simply that the caterpillars of the spectacular Cairns Birdwing, Ornithoptera priamus euphorion, will eat nothing else, so a vine guarantees frequent visits from Australia’s largest butterfly. A couple of days ago I saw the first female of the season laying her eggs on it:
These very large butterflies hover to feed and they hover – very briefly – to lay eggs too: one dab under a leaf and off she will go again. She will repeat the process dozens of times in a single session, then fly off to rest, feed and perhaps mate again.
The eggs hatch into dark spiny caterpillars which turn greyish as they grow to finger-size, then pupate in leaf-like cocoons before emerging, months later, as adults. Clicking here will take you to a collection of my older photos showing males, females, caterpillars and cocoons.
A word of warning from the Wet Tropics Management Authority: Growing the native rainforest vine Dutchman’s Pipe (Aristolochia tagala) will encourage regular visits by this impressive butterfly. However, beware of the exotic Dutchman’s Pipe (Aristolochia elegans) which is poisonous to the Cairns Birdwing caterpillars.