Caring for a Caterpillar of Hippotion scrofa, SPHINGIDAE
(Photo: courtesy of Bec Watkins, Tarragindi, Queensland)
Because so few Caterpillars of Australian lepidoptera are known, often the only way to identify the species of a Caterpillar is to care for it, and rear it to an adult butterfly or moth. This is because most of the naming and classification taxonomy of Australian butterflies and moths was done over 100 years ago on specimens caught in Australia but taken to the British Museum in London, where the entomologists had no idea of the life histories of their specimens. For example: in these webpages, we have pictures of caterpillars in the webpages of only about 800 species, compared with over 4,000 webpages for species for which we have adult moth or butterfly pictures.
Over the last 100 million years: various plants have evolved into over 100 different plant families, each producing different poisons to stop Caterpillars eating them. Meanwhile the Caterpillars have evolved into over 100 different families, many of which are equipped to cope with the poison from one plant family. So if you can find the name and family of the Caterpillar's foodplant, then that will help identify the Caterpillar.
Also different species of Caterpillar have adapted to various different climates, so the location where a Caterpillar is found can be a good clue to its identity.
For people wishing to care for a Caterpillar that they have found,
this is what we suggest:
take your Caterpillar into captivity to keep ants, spiders, wasps, and parasitic flies from attacking it.
Remember that if nature is in balance, then every pair of adults will produce only 2 viable adults in the next generation. So if a female lays say 1,000 eggs, of which perhaps 500 hatch successfully into Caterpillars, then on average 498 will die before reaching maturity. The chances of your Caterpillar surviving in the wild are very much slimmer than if you rear it carefully in captivity: protecting it from predators and parasites. I recommend that you carry a little plastic bottle whenever you go out, for taking any Caterpillars that you find into protective custody.
Put the Caterpillar gently (larvae bruise easily) into a clean dry glass bottle (so you can observe when the adult moth emerges), with some dry sand or soil at the bottom, and cover the mouth of the bottle with some material and an elastic band, or the lid with some little holes punched in it.
To transfer the Caterpillar: maybe put a leaf in front of it, and then gently tickle the rear of the caterpillar with something to encourage it walk forward onto the leaf, then you can put the leaf with the caterpillar on it into the jar. It is wise never to touch a Caterpillar as the hairs on many species break easily and can cause skin irritation and other medical problems.
Many Caterpillars are fussy about their humidity: some like dry conditions, some wet. The sand or soil helps control this. Many Caterpillars get quite thirsty: if your animal looks a bit dry: try dipping new food leaves in water before giving them to the Caterpillar. Too much water: then mould attacks the Caterpillar. Too little: the Caterpillar can die of dehydration. Every species has a different balance point.
If possible, offer the Caterpillar some leaves of the plant on which it was found. But Caterpillars are often found after they have fully matured and are wandering about looking for somewhere to nice pupate, so do not be surprised if your Caterpillar declines to eat.
If it does feed, change the leaves and remove the droppings every 2 days. Finding food may not be easy, especially if the Caterpillar was found just wandering about. Some feed on the algae and lichen on old stonework for example. The best that can be done if you found it when it was just on walkabout is to put several different kinds of plant leaves in the jar, and see if it eats any: If so take all the others out and keep giving it that. If it declines, keep putting different plant leaves in. Some Caterpillars are very fussy, and many will eat only one particular species of plant. Do not leave leaves for more than two days: they rot and grow mouldy. If all else fails, you could try flower petals or bits of apple, which many Caterpillars will accept.
In due course, with any luck, the Caterpillar will pupate, maybe on the jar, the lid, in a curled leaf of the food plant, or in the sand. It is best not to disturb the animal while this is happening. Pupation is usually signalled by it ceasing to feed. In pupating, excess fluid is expelled. Dry sand or soil in the container is good to absorb that away from the pupa.
When pupation is complete (maybe several days), gently (the pupae bruise easily too) take out any loose droppings and excess food plant which would otherwise go mouldy. You should provide some twigs for the new adult, when it does emerge, so that it can hang upside down, as most Lepidoptera need to do this for their wings to expand properly. You then have to wait. Some adults emerge in 2 weeks, some in 2 years, so this may require some patience. The time depends on the species, the season, the weather, how much food it ate, and just how it feels.
Rearing Caterpillars is a great art, and one learns by trial and error, and we mean a lot of error. Dont expect to get it right first time.
Your patience may also go unrewarded: a high proportion of Caterpillars get infected with parasitoids. These are usually fly or wasp species that lay their eggs on or in the Caterpillar, and when they hatch, the fly or wasp grub eats the Caterpillar from the inside. This tends to make the Caterpillar upset and wander about instead of hiding on its food plant: and so these are the caterpillars that are most often found. So if a bunch of flies or wasps come out the pupa, do not be too surprised. These flies and wasps are actually very important. If that is what you get, consider saving them and donating them to your local museum together with information about the Caterpillar, especially if you were able to photograph your Caterpillar. The information on the various species of wasp or fly that parasitise each species of Caterpillar is very important ecological information.
Once you have an adult moth or butterfly, make sure it does not beat itself to a frenzy (butterflies and moths basically do not like being kept in jamjars): a spell in the refrigerator at five degrees Celsius (not freezing which kills them) is a good way of putting them to sleep. Then you may finally be able to photograph it, and identify it from pictures in these web pages, or in books, or with the help of your local museum.
Frequently Asked Questions about Caterpillars
(updated 18 February 2013, 30 January 2018)