Caterpillar identification is not completely necessary but it can be very useful when you're trying to stay one step ahead of what's going on in your garden. Identifying caterpillars as soon as you see them will save you time. You don't want to be caught napping here.
Caterpillars can demolish much of your hard work, often in just a few days. The problem is often worse in small or newly established gardens.
The 'Cabbage butterfly' name refers to two species of fairly obscure butterflies, white-ish with black wing tips and spots. They belong to the family Pieirdae. Sometimes they're called simply 'Large White' and 'Small White'. The wing span is roughly 3.5 - 5 cm. They innocently flutter about during the daytime amongst your precious seedlings, looking for a place to deposit their eggs. They prefer to lay their eggs on plants from the cabbage and the mustard family, and the younger the caterpillar food, the better.
The cabbage butterfly larvae from the two species differ a little more than the adults. They also behave differently.
The offspring of the Small White is a green caterpillar with tiny yellow dots. It's shaped like a small cigar and grows to about 2.5 cm, which is not very large in the world of caterpillars. It lies flat along a stem or a leaf vein to avoid detection. Pick it up and it won't struggle or wriggle much. The caterpillar feels velvety soft due to its fine, short hairs.
The caterpillar from the Large White is yellow or pale green with black markings. It doesn't bother to hide because it taste bad to predators, and can be found exposed and in large numbers.
This moth from the family Noctuidae is also called 'looper moth'. It's an obscure brown moth with lighter coloured squiggly markings. It has a wing span of about 3-4 cm. The looper moth is active during the night, therefore it's not often noticed.
The caterpillar is often called just 'looper', and the name refers to the way it tends to hold itself in a characteristic arching fashion. Its middle section lacks real legs. The critter reaches a length of 5 cm before transforming into the caterpillar cocoon. The most common colouring seems to be light green with some faint white stripes. Related loopers have other colours, such as olive green. This caterpillar is not fussy with its food and can be found on a vide range of plants.
The Tiger Moth in the picture is an Amata spp. member, which produces smallish brown, furry larvae which I have found on many of my plants. They don't seem to be as destructive as some other caterpillars, but worth keeping an eye on.
Now that you're done with caterpillar identification it's time to take action.
Most of the larvae are soft and easy to pick. They don't bite but large caterpillars may hang on to your fingers with their feet. Watch out for the hairy grubs, the bristles are sometimes poisonous and will give you a rash. Wear gloves.
Chickens, ducks and some other birds love to eat caterpillars. A chook pen is highly recommended.
There are many beneficial insects that will dine on caterpillars. Encourage them and you'll have reduced needs for insecticide.
Create a barrier that prevents the flying insect from laying its eggs. Mosquito netting or old curtains can be helpful, but take into consideration that they are also a barrier to sunlight.
Sprays made with garlic, chilli or soap are a big help in the protection of vegetables. However, these will also kill beneficial insects.
Some gardeners swear by the use of torn egg shells scattered underneath the plants. Apparently the butterflies are not that clever, and they'll think this area is crowded already. And they move on.