As summer winds down, caterpillars seem to be everywhere—munching milkweed, hiding among tomato leaves, or spinning webs in trees. Some will become butterflies, while others will turn into moths. Look closer and meet some interesting garden caterpillars, with tips for identifying them, understanding what they eat, and knowing which ones to leave undisturbed.
All butterflies and moths have similar life cycles—egg, larva (caterpillar), pupa, and adult. Caterpillars are near the bottom of the food chain, providing protein-rich nourishment to many birds, bees, bats, frogs, snakes, toads, and small mammals. There are about 12,000 species of moths in North America, and many are important pollinators. The larvae of a few just eat dead leaves, but most like the lush green ones better. If you are finding the leaves on some of your plants are suddenly being eaten, look closely for a caterpillar!
Monarch Caterpillar
We have had a bumper crop of monarch caterpillars on the milkweed this year and find chrysalises in the strangest places. The newly emerging butterflies are generally the only hint that a chrysalis has been hiding among the basil plants, attached to an eggplant leaf, or dangling from a plant support.
Milkweed Tussock Moth Caterpillar
Like the monarch caterpillars, the larva of the milkweed tussock moth, also called the milkweed tiger moth, eats only milkweed, which makes them poisonous to predators. It is a very hairy caterpillar with some orange and black coloring that a monarch butterfly would have. The moth it turns into, however, is not brightly colored at all, just plain brown.
Tomato and Tobacco Hornworms
The hornworms, which are sphinx moth larvae, will pop up on the tomato and pepper plants. They are so well-camouflaged that I don’t usually notice them until much foliage has disappeared. Let it be if you find one with white cocoons on its back. A braconid wasp has laid its eggs on the fat, juicy caterpillar, and when those larvae hatch, they will eat the caterpillar from the inside out. Tiny braconid wasps are beneficial insects you want to have in your garden.
See how to deal with tomato hornworms!
Hickory Tussock Moth Caterpillar
The hairy, white, hickory tussock caterpillar likes tree leaves, including hickory, oak, maple, and ash. This is one furry critter you don’t want to touch. It has barbed hairs that are toxic and can embed in your skin and cause irritation or a rash. After pupating, it will turn into a brown and white moth.
American Dagger Moth Caterpillar
The dagger moth larva is another hairy yellow caterpillar that you should avoid touching. It has five long black spikes of hair, sometimes called pencils—two pairs near the head and a single one at the rear and cause a burning or stinging sensation that may lead to a rash with contact. It eats tree leaves such as oak, maple, birch, and ash. After pupating, it will emerge as a drab gray and white moth.
Tiger Swallowtail Caterpillar
The oddest caterpillar I have found so far this summer is the larva of the tiger swallowtail butterfly. It is smooth and green with faint blue dots. The googly eyespots are fake, just there to scare away predators. It also has a stinky organ near the head called an osmeteria that it pops out to ward off threatening critters. It also eats tree leaves: cherry, apple, and ash, which are its favorites.
Fall Webworm
The fall webworms are back. They make their nests at the tips of the branches and feed only on the leaves within the nest. They expand the nest to include more leaves to chew on as they eat. Eventually, a small nest becomes a huge, ugly mass of crawling caterpillars. They will eat many trees species, including apple, cherry, hickory, birch, oak, ash, and willow trees, but lilacs and other ornamentals can also prey on their voracious munching. Since they feed for a month or more, a severe webworm infestation can defoliate a small tree. They overwinter in the soil as a pupa and emerge as a small white moth in late spring.
Woolly Bear Caterpillar
I am still looking for a wooly bear caterpillar, the larvae of the Isabella moth. It likes to eat dandelions and plantains—a common weed found in many yards; no harm is done there. The black and brown wooly bear has long been used to predict the harshness of the coming winter. According to folklore, the wider the brown band in the middle, the milder the winter will be. Read all about the Woolly Bear Caterpillar and Weather Prediction!
Interested in butterflies? Learn about planting a butterfly garden.
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When I can't stand looking at the webs any longer I resort to the stick-with-a-nail-in-it cure. I just poke the stick into the nest, twist as much of the nest as I can around the stick, and pull it down. The nail, positioned at a right angle to the stick will keep the nest from sliding off before you get it down. A dunk in a bucket of soapy water kills the caterpillars. Helpful hint - don't stand underneath the nest while doing this or you will get rained on with caterpillars and their poop! The ones that fall from the nest may climb back up the tree to re-infest it so I stomp on those wayward buggers. Not knowing how tall your pecan trees are, this might not work. You could try using a high pressure hose to knock the nests down. You can ward off next year's caterpillars by looking for their shiny brown eggs on the bare limbs over the winter and scraping them off. Another thing that might help is to inoculate the soil around the trees with beneficial nematodes which will eat the pupae living in the soil.
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