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by Pat Jaquith
pat@westvalleynaturalists.org

Saltmarsh Moth with eggs and three views of Saltmarsh Moth caterpillars

Connecting a caterpillar you find with its parent butterfly or moth is an interesting puzzle. Read on to see some of the connections I have made in the West Valley.

The insect at the left is often described as resembling bird poop; it is the 4th instar of the egg developing into a caterpillar. The green caterpillar is an early version that morphed into the brown stage just before forming a pupa where it would continue its development to become a Two-tailed Swallowtail butterfly.

Moth eggs undergo 4 transformations called “instars” before becoming a caterpillar. Each instar eats, grows, and takes on a new look. In the case of the Tussock Moth, this is the first time I have seen the 4th instar and the final caterpillar. There was a time lapse of 10 days between my discovering the two final phases on leaves of a Forsythia shrub. The caterpillar will eat, grow, and pupate: its final transformation. When it comes out the next season, it will be in the Moth phase.

Chasing beautiful butterflies is wonderful exercise! Chasing down the parentage of caterpillars in all their versions is a time-consuming mental exercise. We’d love to hear from you if you have butterfly adventures to share!