NORTHERN CALIFORNIA – In the summer months you get to see a lot of really lovely butterflies and interesting-looking moths in the Berryessa Snow Mountain National Monument region, but keep an eye out for their babies, too.
Although some of them have faces only their mothers could love, caterpillars are really quite fascinating.
Looking very much like a tomato hornworm, the flat-faced tobacco hornworm (Manduca sexta) caterpillar is bulky and bright green. It’s the larval stage of a kind of very large sphinx moth.
You’ll usually find it munching through the leaves, stems and flowers of wild native flowering tobacco (like Nicotiana attenuate) and non-native tree tobacco plants (like Nicotiana glauca), leaving behind untidy piles of dark “frass” (droppings) on the foliage below them.
Like all hornworms, these guys have a thick pointed protuberance located on the last segment of their body that sticks straight up. It’s not a stinger, it’s more like an adornment, and its color can change as the larvae ages.
When this caterpillar is mature enough, it will drop from the plant and burrow about 4 inches into the ground. There it will form a pupal cell (chrysalis) around it.
The elliptical-shaped cell has an obvious loop at one end which will eventually hold the developing moth’s mouth parts. The pupa will over-winter in the ground and emerge as a moth in the following summer.
And then there’s the caterpillar of pipevine swallowtail butterfly (Battus philenor). Hatching from tiny rust-colored eggs that can be laid anywhere on the pipevine plant, the larvae start out reddish-brown in color with orange spikes.
As the caterpillars mature, the spikes remain but the rest of the body turns dark black. They can be found wandering around pipevine plants – the only plants they are built to eat – feeling their way with the fleshy “antennae” that protrude from either side of the head.
Since the host plants they eat contain a toxic alkaloid, the caterpillars are toxic, too, and they’re equipped with a pair of foul-tasting “horns” that they can brandish at any bird or lizard foolish enough to try to eat them.
When mature, these caterpillars don’t go underground. Instead, they will climb into a nearby tree (or fencepost) and attach themselves to it with a suspension line of silk.
Once settled, the caterpillar then encases itself in a chrysalis (which can be green or brown) and wait to emerge later in the season as a butterfly. Pipevine swallowtails can have two broods a year.
Third up is the tussock moth caterpillar (Orgyia sp). Its face and body are covered in hairs and piles of prickly tufts (that can produce an allergic reaction in people who are sensitive to it).
The hairs not only help to identify this particular caterpillar, they are also used to build its cocoon after it matures. Inside the cocoon, the caterpillar will form a hard casing around itself as it pupates, and the following season a moth will emerge.
What’s most interesting about this species is the fact that although papa moth is a rather nondescript guy with brownish-gray wings, mama tussock moth is very special.
Fluffy and fat when she emerges from her cocoon, she is completely wingless. That’s right; she’s a moth with no wings. Because she can’t fly to her love like the females of other moth species, mama tussock moth will wander out onto the end of a branch and exude a pheromone that lures the males to her.
After mating, she then lays hundreds of eggs inside a silk sac that is made in part of the same hairs that made up her cocoon when she was younger. She’s an awesome recycler!
So, although they may look creepy to everyone but their mothers, caterpillars can make for some interesting studies. And they are an essential part of the ecosystem. They are, after all, baby butter-flies and moths, the early forms of the world’s best pollinators. We couldn’t do without them.
So, don’t errantly squish “icky looking” caterpillars when you come across them. In fact, plant flowers and shrubs in your garden that help to feed them. The more caterpillar-friendly your garden is, the more butterflies and moths it will attract.
Tuleyome is a501(c)(3) nonprofit conservation organization based in Woodland, Calif. For more information visit www.tuleyome.org . Mary K. Hanson is a Certified California Naturalist and author of the “Cool Stuff Along the American River” series of nature guides available at www.lulu.com .