Photo: Eastern Tiger Swallowtail Caterpillar, Judy Gallagher
Judy Gallagher is an ASNV board member and a regular surveyor of local wildlife who also captures photos of what she sees, in particular the less common species. Here are some observations from her most recent survey.
I always look carefully at bird poop on leaves because every once in a while it proves to be something else.
Judy Gallagher
At Occoquan Regional Park recently, the "bird poop" was a tiny Eastern Tiger Swallowtail butterfly caterpillar.
Judy Gallagher
Looking like something distasteful is one of several strategies used by the Eastern Tiger Swallowtail, our state insect, to keep from being eaten by predators. The caterpillar also has a defense organ called an osmeterium which can be everted when it feels threatened. Not only does this startle the predator, but it looks a bit like a snake tongue. The osmeterium emits a foul odor that repels ants, spiders, and small praying mantises.
Judy Gallagher
Before transforming into a chrysalis, the caterpillar molts its external skeleton several times and becomes bigger. In its later stages, it is too big to disguise itself as bird poop. The defense strategy for bigger caterpillars is looking like a snake with enormous eyes. The large eyes give the illusion that the caterpillar is even bigger than it really is.
Judy Gallagher
The adult butterfly also has a defense strategy. Most Eastern Tiger Swallowtail adult females are predominantly yellow, but a small percentage of them are black. This makes them look like Pipevine Swallowtail butterflies which are toxic to birds.
Judy Gallagher
The dark Eastern Tiger Swallowtail females are less vulnerable to predation, but alas, gentlemen Eastern Tiger Swallowtail males prefer blondes. It's a tough world out there.
View all of Judy’s Observations from Meadowood articles here.