Gloriously Fat and Sassy (Spicebush Swallowtail caterpillar)
I planted a Spicebush (Lindera benzoin) in my backyard (ok, so it's not quite planted yet... it's still in its nursery pot... so let's say I "placed" a spicebush in my backyard) in April of this year, and I'm now on my second batch of Spicebush Swallowtail caterpillars!
The Spicebush is one of the most common swallowtails in West Tennessee. Their caterpillars have some great passive defense mechanisms. The most obvious are their large false eyespots: to a potential predator, they look more like the head of a snake than a tender yummy caterpillar. They also spend most of the day folded up inside leaves, where they aren't very visible. Young, small caterpillars will nibble a line through a leaf, then fold just a section of the leaf around themselves. Larger caterpillars (like this guy) fold up the whole leaf.
When they first hatch out, the tiny caterpillars look like little brown bird droppings (another good defensive strategy -- who wants to eat poo?). As they get bigger, they look like slightly more elaborate, brown and white bird droppings. When they're almost full-grown, they take on the bright green hue seen here.
As a final defense, these caterpillars each come equipped with an osmeterium, a forked, fleshy organ just above the caterpillar's head. If a predator threatens one (despite its resemblance to poo or a snake - gotta be one brave predator already!), the caterpillar can suddenly display the osmeterium, which emits a pungent, disagreeable odor, which will hopefully confuse and/or repulse the predator, driving it away. (If the predator DOES persist through all these defenses, it ends up with a tasty little morsel - the caterpillars aren't poisonous.)
Altogether fascinating little buggers, and I can't wait to go out into the backyard each day and check on their progress!