Old World Swallowtail Care

This guide is written in regard to Old & New World Swallowtail Butterflies (available to order here), including the species Papilio machaon; P. polyxenes; P. stabilis; & P. zelicaon.

Eggs should be kept in closed plastic containers to prevent them drying out - these eggs are more sensitive to changes in humidity than other butterfly species. They will hatch within days as the egg stage is very short, turning black before the tiny caterpillar hatches.

You can add leaves to their container once the caterpillars hatch, but do not add any prior to this as leaves will release moisture and this often causes the eggs to mould before hatching, killing them. Once the larvae have established and are feeding well, they should be moved to mesh cages as these species benefit greatly from air flow - stagnant air seems to cause disease which quickly spreads through the larvae. Preparing some potted host plants in advance is a good idea, as these always do better on living hosts.

These caterpillars do best using Fennel as a host plant - however others such as Carrot, Parsnip, Dill, Parsley, and their wild counterparts are also accepted by larvae.

The photo above illustrates a Papilio polyxenes asterias larva in the final instar. After another few days of feeding on Fennel, it will find somewhere to secure itself and pupate - pointing upwards in the typical Papilioniidae way.

Caterpillars grow fairly quickly, usually pupating by about week 3. Depending on the time of year, the adult butterfly will then emerge in 2-4 weeks, or the following spring. Broadly, pupae formed between April and August will emerge the same season, whilst those in September/October will likely overwinter.

Pupae can be left in situ if conditions are right, or moved to a different setup for pupae - following the care guide for pupae will produce best results. Overwintering pupae should be stored somewhere cool where they cannot be eaten by small mammals or other predatory insects - a plastic container in the fridge is usually fine, but note that this should remain closed as most fridges have dehumidifiers which will dessicate pupae if not protected. Alternatively, any out-house subject to natural temperatures will suffice, storing the pupae in e.g. a biscuit tin.

Adult butterflies can be cared for according to this guide. They are very straightforward, simply requiring ample space to fly and a food source. The photo below shows an adult Papilio machaon.