Glossary

Chrysalis (KRIS-uh-lis) is the pupal stage of a butterfly — the protective casing inside which a caterpillar transforms into its adult form. The chrysalis is not a cocoon. A cocoon is spun from silk by moth caterpillars as an outer casing around the pupa. Butterflies do not spin cocoons. The chrysalis itself is formed directly from the caterpillar’s own skin, hardening into a shell that contains and protects the transformation within.

Both structures serve the same purpose — sheltering the pupa through its most vulnerable stage — but they are produced differently and by different insects. Understanding the distinction matters for habitat gardeners because the structures require different conditions and are found in different locations.

In the Santa Cruz Mountains, butterfly pupae form chrysalises in a variety of locations depending on species — attached to plant stems, tucked beneath leaves, anchored to woody debris, or suspended from bark. Moth pupae may overwinter as pupae inside silk cocoons in leaf litter, soil, or hollow stems. Both are present on native plants throughout the San Lorenzo Valley from late summer through early spring.

The Painted Lady (Vanessa cardui), one of the most visible butterflies in the San Lorenzo Valley, pupates on its larval host plants — including Common Yarrow (Achillea millefolium) — forming a pale, spiny chrysalis attached to stems and foliage. This is one reason the overwintering rule matters: cutting back Yarrow and other native perennials before daytime temperatures hold consistently above 50°F risks destroying pupae before the adult butterfly has emerged.

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