In the world of butterflies and moths, caterpillars look nothing like their adult counterparts. If they were people, you’d have a terrible time matching the grown-ups to their elementary school photos. Often, I’ve noticed, if the caterpillar is colorful or interesting, the adult is dull, or vice versa. This week’s subject, however, is charismatic as a caterpillar and as an adult. 

Western Tiger Swallowtails are one of the largest and most distinctive butterflies in Oregon. There are several types of swallowtails in our area, but these are the most common at Mount Pisgah. 

The caterpillars grow throughout the late summer and early fall, and spend the winter inside a chrysalis. These photos are from last year, when I found a caterpillar on the Jette Trail and revisited it over a few weeks. 

Papilio rutulus caterpillars are masters of disguise. When they’re very small, they, like many other swallowtails, can be mistaken for bird droppings. Smart! There’s probably not a better way to appear distasteful to hungry birds.

When they’re older, they turn green and develop colorful purple, black and yellow eyespot markings above their heads. To further cement the snake-like look, these caterpillars have an organ called an osmeterium that they deploy when they’re disturbed. Not only does it look like the forked tongue of a snake, but it also gives off a foul odor to dissuade predators. 

The last time I saw this caterpillar, its body had filled out and it was resting on a silk mat. In the right light, it looked like it was levitating. Apparently, the web is meant to pull the outer edges of the leaf toward each other, and give the caterpillar yet more protection as it gets ready to transform into a pupa. This particular leaf wasn’t cooperating, but it allowed me to get some pictures.

Stay curious!

See more of Karen’s work here.


The BugLady on swallowtail caterpillars: Accessed 10/5/22.

The Liang brothers’ photo diary on raising Western Tiger Swallowtails (also see their August entries for later stages: Accessed 10/5/22.