Amazing spicebush swallowtail

September 28, 2018

I’ve seen some amazing things this year on my hikes. Very few things, however, make my friends and family look in astonishment like last week’s encounter with this spicebush swallowtail caterpillar.

Some might think it is a Pokémon, but no, this is a real creature crawling around the forests of Kankakee County.

This one happens to be orange, but you might run across a green or yellow version as well.

I have read that the caterpillars can change colors in reflection of the host plant’s leaf colors during the season … green during the summer and yellowish/brown for the fall.

However, the most striking feature are those amazing eye spots that really draw you in. The spots are designed to make predators think maybe this isn’t a caterpillar at all but instead a smooth green snake or a tree frog.

Behind those eyes also exists a forked horn-like organ (called an osmeteria) that can extrude out if it senses danger. This horn looks an awful lot like the tongue of a snake to me.

We seem to be on the Northern edge of observations of this species according to INaturalist. There is a clear line that cuts off anything north of Peoria diagonally to Kenosha, Wis.

The caterpillar depends on host plants from the family Lauraceae and in particular the native spicebush (Lindera benzoin), and, in my case, sassafras trees (Sassafras albidum). Both plants don’t seem to occur much further north of here either.

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