Caring for Eggs & Caterpillars
Upon receiving your eggs or caterpillars, they will need to be placed into a suitable environment. Very simply, a plastic tupperware container or ‘takeaway tub’ with some tissue paper at the bottom is ideal for most species - this is because it maintains temperature and humidity at a stable level. If this is not provided, eggs or caterpillars may die.
The photo illustrates Large White (Pieris brassicae) caterpillars being reared using the method described.
You will also need supply of host plants, each species of butterfly or moth has its own. In many instances the caterpillars may accept multiple hosts, but others will only feed on a single kind of plant.
It is often easiest to find some hosts growing locally so that you can access these as required for feeding, but you can also buy plants online to use for rearing or grow on for future breeding seasons.
Do not add water or heat to your eggs/caterpillars. Adding water is likely to drown the developing caterpillar before it manages to hatch - a very common mistake. Keeping the hatchlings in a plastic container ensures they do not dehydrate, and once they start eating leaves, the caterpillars should be getting enough moisture from their diet.
You can continue rearing larvae in plastic containers, providing them with bigger ones as they grow, however by the third or fourth stage they will often do better in a mesh enclosure - net rearing tends to be better due to improved air flow as it prevents mould outbreaks and reduces potential spread of disease between larvae.
To keep your host plant leaves fresh, it is a good idea to stand some host plant stems in water. Some plants and trees last surprisingly long, like Liquidambar which can last weeks, although others have a shorter 'shelf-life.' If there are holes between the stems where larvae may fall into the water, you can fill these with cotton wool, tissue paper, or similar.
The way you treat your caterpillar at pupation should depend on what species you are rearing. It is important to know whether your caterpillars will burrow, spin a cocoon, or suspend themselves prior to pupating.
For burrowing species, a large container either with sterile compost at a depth of 10cm, or with tissue or sawdust. We typically use tissue and newspaper for most burrowing species as it is clean and simple. After about two weeks, you can carefully dig up the pupae and incubate or store as appropriate for that species.
Should the larvae spin cocoons or suspend themselves to pupate, you do not really need to do anything other than ensure their food is fresh until they have finished feeding.
An example of a Comma (Polygonia c-album) caterpillar suspending itself in a J-shape prior to pupation.