For people wishing to care for a caterpillar that they have found, this is what we suggest:
take your caterpillar into captivity to keep parasitic flies and wasps from attacking it. Remember that if nature is in balance, then every pair of moths will produce only 2 more viable moths in the next generation. So if the female lays 1,000 eggs which hatch into 1,000 caterpillars, only 2 on average will survive to become adult butterflies or moths. So the chances of your caterpillar surviving in the wild are much slimmer than if you rear it carefully in captivity.

Put it gently (caterpillars bruise easily) into a clean dry jamjar with some dry sand at the bottom, and some holes punched in the lid. To transfer it, maybe put a leaf in front of it and then gently tickle its rear 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: the hairs on many species break easily and can cause skin irritation and other medical problems. Give the caterpillar some leaves of the plant on which it was found if possible, and change these 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: caterpillars are very fussy, and many will eat only one particular species of plant. If all else fails, you could try flower petals or bits of apple, which many caterpillars will accept.

Many caterpillars are also fussy about their humidity: some like dry conditions, some wet. The sand 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.

In due course, with any luck, the caterpillar will pupate, maybe on the jar, the lid, the food plant, or in the sand. Then 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.

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.

cocoons of parasitic wasps from a Manulea replana caterpillar, ARCTIIDAE

Once the 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: that kills them) is a good way of putting them to sleep. Then you may finally be able to identify it from pictures in these web pages, or in books, or with the help of your local museum.

Good hunting.

Female adult moth of Anisozyga insperata, GEOMETRIDAE

Link to
Frequently Asked Questions about Caterpillars

Australian butterflies

Australian caterpillars

Australian moths