How to Keep Fall Caterpillars Alive Until Spring

Rearing Caterpillars, Cocoons, and Chrysalides Over the Winter

A banded woollybear caterpillar under a leaf

Ed Reschke / Getty Images

It's easy to raise a fall caterpillar you have collected and keep it alive through winter. By knowing what type of caterpillar you have and understanding what life cycles it will go through while in your care, you can provide a safe home for your caterpillar during any season.

Caring for Changing Caterpillars

The key to caring for a caterpillar at any time of year is to provide conditions that mimic the caterpillar's natural cycle and habitat through seasonal changes. For example, some caterpillars survive winter by burrowing under leaf litter or squeezing into bark crevices, while others pupate as cooler weather approaches and remain in this state until spring. In other words, caterpillars don't always stay in caterpillar form through changing weather conditions.

You will need to provide food for your fall caterpillar so that it can grow, just as you would for a caterpillar captured during any other time of year. Eventually, the caterpillar will stop feeding and may become more sluggish. This is a sign that it is preparing itself for winter, and what comes next for your caterpillar depends on the species. At this point, you need to know what types of changes your caterpillar will go through to anticipate its needs.

Overwintering Stages of Common Butterflies and Moths

You should find out whether your caterpillar is going to stay in the larval stage all winter or pupate. These lists tell you the common species that will remain a caterpillar through winter and those that will transform into a cocoon.

These butterfly families tend to stay in the caterpillar stage through winter:

Pupae

These butterfly families tend to spend the winter as a cocoon or chrysalid:

  • Cup moths (Limacodidae)
  • Flannel moths (Megalopygidae)
  • Swallowtail butterflies (Papilionidae)
  • Whites and sulphurs (Pieridae)
  • Tiger moth caterpillars (Arctiidae)—some

Most loopers, inchworms, and spanworms, or geometer moths (Geometridae) spend their winters as pupae, but some will remain caterpillars.

Knowing your species of caterpillar will prepare you to care for it as it changes.

Keeping Caterpillars Over the Winter

Keeping caterpillars over winter is easier for species that remain in the caterpillar stage than those that pupate. When caring for species that overwinter as caterpillars, simply clean any remaining frass and food plants from the container and cover the resting caterpillar with a layer of dead leaves.

Move the container to a porch, unheated garage, or shed so that the caterpillar can experience natural temperatures and conditions, keeping the humidity as close to that of a caterpillar's natural habitat as possible. If the caterpillar is kept in an environment that is too dry, it may desiccate and die. When spring arrives, watch for signs of activity from the caterpillar.

Keeping Cocoons or Chrysalides Over the Winter

Preparing Butterflies to Pupate

Many types of butterfly caterpillars overwinter as chrysalides. Provide some twigs or stems for these caterpillars to give them something from which to suspend themselves and pupate. Make sure there is enough space for the cocoon to dangle. You can accomplish this by securing the twigs with clay at the bottom or cutting pieces that will fit tightly against the edges of the container without falling.

Preparing Moths to Pupate

Moth caterpillars typically pupate in the soil, sometimes incorporating leaves into their pupal cases. If you have captured a moth caterpillar, place a layer of peat moss and leaves in its container. Once it spins a cocoon, you can remove any remaining leaves. Be careful not to disturb the cocoon when clearing the container.

Storage and Care of Pupae

Caterpillar containers always need to be moved to an unheated area for the winter and this is most important for caterpillars that pupate. Pupae are especially sensitive to changing weather conditions, so you must choose their location wisely. If you are going to store your pupae or caterpillars outdoors, be sure to keep them out of the sun. Even on a cold winter day, a container can warm up considerably if placed directly in the sun's rays. This might lead to premature emergence, or it could dry out the pupae.

As it gets closer to spring, lightly mist the pupae with water to simulate the increased humidity and moisture of the changing seasons. When spring returns, try to keep your caterpillar or pupae cool until other members of the same species are emerging in the environment around you. If you aren't sure, wait until the trees in your area grow their leaves for the season before moving the container to a warmer location.