Article by Mike Moore
As a Lepidopterist you may want to raise butterflies and moths at home.
You may have a host of plants in pots in the hope of collecting an egg or caterpillar.
Most butterflies can easily be raised in jars. Cabbage White butterflies are good to start with. Skippers, however, because of their long life cycle, most of it spent as a caterpillar, are more difficult to raise in jars.
Raising Butterflies in Jars
Screw-top coffee jars, Vegemite jars, and pasta sauce jars are good to use. Sauce jars are square and therefore do not roll when placed on their side.
Do not use pressure seal jars. Caterpillars are hydrostatic organisms (full of fluid) and could be affected by pressure changes in opening and shutting the sealing lid.
Some collectors do not like using plastic containers, as plastics release hormone-like chemicals and these may upset the caterpillars’ development.
When hatching caterpillars from eggs I usually start with a small jar, as these only require a small amount of plant material and the tiny caterpillar can be found easily when cleaning the jar or replacing food. However, a small amount of plant material tends to dry out quickly and needs more regular replacement. This is critical when an egg is developing so that when it hatches the hatchling has something good to eat.
Some people wash and dry jars regularly. However, as long as the caterpillar poo (frass) is removed completely each time you add new food you do not need to clean the jars. If frass starts to go mouldy then you will need to clean the jars thoroughly.
Ideally, jars should placed where they can be easily and regularly accessed. They must never be in direct sunlight but placed in a location subject to natural rhythms of light and dark. This can be difficult in a household. Try placing a tea towel over jars, keeping them permanently shaded but still able to detect the normal diurnal cycles.
The Paper Bed
Cut a piece of paper to lie flat in the jar. Kitchen paper towel or toilet paper will do.
Cut it to fit, or almost fit, the jar. If it is too big it provides enticing nooks and crannies for caterpillars so at cleaning time they might be damaged accidentally by handling.
The paper is valuable for the following reasons.
When cleaning the jar or replacing food, first look under the paper from outside of the jar to discover where caterpillars are located. Many hide under paper and careless handling could damage them. Then use tweezers to pull everything out carefully.
A Piece of Bark
If a butterfly species lives on or near the bark of a tree or shrub, put a piece in the jar.
Butterflies have very specific food requirements. Some butterflies can be transferred successfully onto other food plants but this is the exception rather than the rule.
Try to utilise the plant species from which they were collected if at all possible.
For young caterpillars, try to provide young shoots. Many plants have within them toxins to stop predation by animals. Young leaves have less toxins, and are probably more palatable for smaller caterpillars.
Ensure moisture levels in the jar are sufficient to keep all of the plant material moist. Caterpillars cannot eat dry leaves. Extra moisture can be provided by placing a wet but squeezed wad of absorbent paper or cotton wool in the jar. Caterpillars do not handle wetness well, so you do not want liquid water free in your breeding chamber.
Ideally, replace the food every two or three days.
Managing the caterpillars
Caterpillars are rather fragile so try to avoid touching them. If you need to clean them or move them, use a paint brush to do so very gently. That is why you need to be careful locating them before you add new food. If caterpillars are difficult to move when you are maintaining the jars, cut off the leaf, twig, or piece of paper bedding underneath, and afterwards place it back in the jar with new food added around it.
When shedding their skin caterpillars will often sit motionless for days and it is imperative they are not disturbed, so use the same technique to cut off the substrate (leaf, twig or occasionally paper bedding) and place it carefully back in the jar after maintenance. If they are ecdysing on the bark, all the better.
The maximum number of caterpillars in a jar depends on the size of the jar and the size of the caterpillars. Some Lycaenid (Blues) species can be carnivorous, but this seems to relate to the amount of fresh food available. In a medium sized (Vegemite-type) jar try two small caterpillars. In a pasta sauce jar, try three small or two larger.
Keeping numbers down in a jar helps if any become diseased. If a caterpillar becomes diseased it inevitably dies, and will probably take any others in the jar with it. If this happens makes sure you do not transfer the disease to the other caterpillars
It is always a relief when the caterpillars pupate. Although disaster can still strike, the tasks of feeding and cleaning are over. Clean out the jar. Have a paper bed in place. Position pupae so it is easy for the adults to emerge. Some species produce hanging pupae (often on the lid) and these need to be placed in a larger space. When adults emerge they need enough room to pump up their wings so it might be good to change the jar to a larger one. Might you use a small vivarium or a hatching chamber?
Another possibility is to remove the jar lid and cover the opening with muslin secured by an elastic band. This aids the drying of both the pupa and butterfly wings.
There is also an option to tip the jar upright, with a circle of paper in the bottom and a climbing stick placed inside.
Do not touch the pupae
Problems I have encountered are usually related to the nature of the food plant
Wanderer butterflies use Milkweed as their food plant. This plant has a sticky white sap which seems to exude non-stop from the cut end of the branches. If this is placed in a jar, the jar becomes sticky with the sap; the caterpillars produce vast amounts of poo; and the whole jar becomes a putrid, sticky mass, in which the caterpillars can become stuck. This is one of those species where it is better to have a cut stem in water in a vase or jar, with the top covered with paper except where it is pierced by the plant cutting. (Otherwise the caterpillars will inevitably fall into the water.) Because the butterflies are exposed, be very careful with any sprays used around the house. Fly spray also kills caterpillars.
Placing a plant piece in water can prolong its longevity but of course you can’t do that in jars. My friend Lindsay Hunt used to use this technique for Candalides species that live on a thin soft climbing parasitic plant called Dodder.
The nettles that Australian Admirals use also present their own problems. As nettles die off, they contract and dry, whilst the caterpillar is trying to make a shelter out of silk and cut leaf. This can make quite a mess in the jar, particularly if the caterpillars are small. What I have done is to let the eggs hatch on the plant in the garden and collected caterpillars when they are larger and easier to see and manage.