A list of 19 types of caterpillars in Wisconsin, including what they look like, where you’re likely to find them, and their lives after they become butterflies or moths.
These are ranked in order of the most common to the rarest, so the list is from most accessible to most complex, which is the hardest to find in our state.
It’s important to note that these caterpillars in Wisconsin may look completely different when they turn into butterflies or moths!
1. Monarch Caterpillar
The monarch caterpillar is black with a white and yellow stripe running down its back. These types of caterpillars in Wisconsin have tufts of orange, brown, and white hair on their sides that look like little legs.
Monarch caterpillars often feast on milkweed plants’ leaves (Asclepias spp.). If you spot one, leave it alone—or at least try to move away from it if you don’t want to crush or accidentally injure it.
Not only are they cool to observe in nature, but they’re also excellent pollinators! The monarch butterfly or moth (Danaus plexippus) larvae feed on Asclepias spp, commonly called Milkweed.
2. Cabbageworm
Just look for a small, green worm with two small black dots, and you can identify cabbage worms. The caterpillar is often found on broccoli and cabbage plants. The adult moth is brown or tan and has dark spots on its wings.
Cabbageworms eat hundreds of plant leaves before they develop into moths. They lay eggs that hatch into larvae, which grow to about one inch long when ready to pupate.
You may notice hairy patches on plant leaves if you have cabbage worms in your garden – piles of caterpillar frass (waste).
3. Woolly Bear
The woolly bear is one of our most well-known caterpillar species—both for its distinctive black and white markings and its status as a harbinger of winter.
This native caterpillar hatches in late summer or early fall, which makes it a great candidate to be spotted on an autumn walk through your favorite park. If you’re lucky enough to spot one, keep your distance!
These types of caterpillars in Wisconsin have hairs that can irritate if they come into contact with human skin. Plus, they’re poisonous.
If you happen upon a woolly bear in Wisconsin during mating season (October and November), look closely at his hind end: male wooly bears have bright red swords sticking out from their rears!
4. Viceroy Caterpillar
The Viceroy Caterpillar (Limenitis archippus) is a type of butterfly caterpillar. They are known for their resemblance to a butterfly, which allows them to fool predators and avoid being eaten.
Although they look like adult butterflies, they are still types of caterpillars in Wisconsin. The Viceroy has a few black lines on its wings, each edged with yellow.
Their back half is white with black spots or stripes, while their front half is dark green with red stripes along their sides and white lines running down each side of it.
Despite looking similar to Monarch butterflies, they do not have orange spots on their wings as adults and only have four legs, while monarchs have five.
5. Large Maple Spanworm
Commonly mistaken for monarch butterflies, Large Maple Spanworm caterpillars are a type of hawk moth that spends its early life dangling from trees.
They love large maple trees like box elders and sugar maples, where they spend most of their time in groups.
The Large Maple Spanworm’s diet consists almost entirely of tree sap it has ingested from its host plants.
These young caterpillars in Wisconsin can be found crawling across branches and trunks during warmer days or hanging upside down on tree bark by day three after hatching.
Their oval bodies are greenish yellow with small black eyespots near both ends, making them appear more colorful than other types of caterpillars in Wisconsin.
6. Variegated Fritillary Caterpillar
The variegated fritillary caterpillar is identified by its orange and brown color. They can grow up to 3 inches long and are known for their heart-shaped pattern with yellow stripes.
The larvae feed on Violets (Viola), thistles, dandelions, blackberries, wild cherries, and ragweed.
Early instar types of caterpillars in Wisconsin tend to favor violets over other plants, but their dietary preferences expand significantly as they mature.
They do not have a common name for their adult stage; however, they are often called Fritillaries or Frits. These butterflies live less than two weeks as an adult before dying after laying eggs to begin a new life cycle.
7. Curve-Lined Owlet Moth Caterpillar
Spiny larvae feed on various deciduous trees and shrubs. These include hackberry, hawthorn, willow, alder, walnut, and birch. The moths are brown with darker spots; they fly from mid-June to early July.
The wingspan is 1.8–2 inches (4.5–5 cm). The caterpillar has long spines along its back and sides. The adult moth does not have these spines.
It feeds at night and hides under bark or other debris on tree trunks or branches during daylight hours.
It lays eggs during May and June, which hatch into caterpillars that feed all summer before pupating in August or September. The adult moth emerges soon after pupation begins and lives for only one week as an adult.
8. Tobacco Hornworm
Tobacco Hornworms are one of Wisconsin’s most common caterpillars. They grow to 11⁄2 inches and develop into beautiful black, brown, and red moths.
These types of caterpillars in Wisconsin can be found on tomato plants, green beans, cucumbers, and just about any other vegetable garden plant!
The easiest way to prevent damage is by handpicking them off your plants. If you find one on your plant, squish it or drop it into a jar filled with soapy water.
Tobacco Hornworms have large amounts of toxins in their bodies, making them very dangerous for humans to eat or touch without protection.
9. White-Marked Tussock Caterpillar
The white-marked tussock caterpillar is one type that can be dangerous for you, your children, and other pets.
The caterpillar is known to produce venom, which can cause pain, itching, and redness on any part of your body with which it comes in contact.
The best way to prevent being stung by a white-marked tussock caterpillar is to stay away from it entirely.
These types of caterpillars in Wisconsin are most active during summer but have also been seen to migrate into areas where they are not typically found.
It’s always important to know what kind of caterpillars are indigenous to your site to avoid unnecessary contact with them.
10. Banded Tussock Caterpillar
As you may know, tussock caterpillars are some of North America’s most voracious caterpillar pests. But what makes them so destructive? For one thing, they feed on a variety of trees and shrubs.
They can devastate entire forests by destroying plants like maples and junipers. The banded tussock caterpillar is even more dangerous than its fellow clusters, as it feeds on evergreens and hardwoods.
To make matters worse, these insects are immune to poison! Scientists aren’t sure why they’re immune; one theory suggests their skin is naturally toxic.
11. Milkweed Tussock Caterpillar
The body is covered in black and white hair tufts, with one line of orange tufts with a black center along the back.
The body is up to 1.5 inches long and relatively thin. The preferred host of this species is Milkweed, as its name suggests.
Despite having different appearances, Wisconsin’s Milkweed Tussock Caterpillars and Monarch Caterpillars are surprisingly similar and are both types of caterpillars in Wisconsin.
Both species favor milkweeds as host plants. But why they consume what they do is what’s intriguing about them, not what they eat!
Heart glycoside is a deadly substance that milkweed tussock caterpillars store in their bodies. Although it doesn’t hurt the caterpillar, it does an excellent job of making it repulsive to many predators dangerous! Blue Jays have been known to throw up.
12. Giant Leopard Moth Caterpillar
Black bristles and properly spaced red rings cover the entire body. It is common to see this caterpillar curl up into a ball as a defensive position.
Giant leopard moth caterpillars eat the fruit and leaves of willow, cherry, cabbage, dandelion, maple, orange, sunflower, and violet.
Wisconsin’s seemingly innocuous types of caterpillars hide an important secret—they grow into gigantic, gorgeous moths!
If you see one, you might mistake it for a Giant Leopard Moth Caterpillar rather than a Woolly Bear Caterpillar.
This species is sometimes called the Giant Woolly Bear, and the two are commonly mistaken. The Giant Leopard Moth Caterpillar’s body is covered in smaller, longer red bands.
13. Parsley Caterpillar
One of the more popular caterpillars in the state of Wisconsin is the Parsley Caterpillar. These types of caterpillars in Wisconsin are most often found on parsley plants and can grow as long as two inches long! When they are fully grown, they will turn into beautiful yellow butterflies.
14. Eastern Tiger Swallowtail Caterpillar
The Eastern Tiger Swallowtail caterpillar is the largest of all caterpillars, with a black body and yellow or green stripes on its sides. They grow to be around four inches long.
When they pupate, they will turn into an orange and black striped butterfly, one of North America’s most commonly seen butterflies.
These types of caterpillars in Wisconsin are often found on members of the Asteraceae family, such as dandelions, Milkweed, and goldenrod.
15. Spicebush Swallowtail Caterpillar
The Spicebush Swallowtail is one of Wisconsin’s more unique types of caterpillars. Its vibrant orange and black coloration is unmistakable, and if you’re lucky enough to find one, you can watch it grow into an equally stunning green and black adult butterfly.
The Spicebush Swallowtail is located primarily in the eastern United States but can also be spotted as far west as Texas.
They are most commonly found on spicebush leaves or other plants from the Rutaceae family. The Spicebush Swallowtail’s body is cylindrical with pronounced segments that make it look like it has a head, thorax, and abdomen like many other insects.
16. Cecropia Moth Caterpillar
These types of caterpillars in Wisconsin can be found on oak, elm, and cherry trees during the spring. They will go through several color changes as they grow. Many people think these are the most beautiful caterpillars in the world!
Once fully grown, it will become a moth with bright green wings that are easy to spot. The Cecropia Moth can be found across North America but is native to Eastern North America from Canada south to Florida and west to Texas.
17. Monkey Slug
The monkey slug is named for its resemblance to slugs. It is reddish-brown and shaped like a worm. It has large, round eyes on the top of its head that give it an uncanny resemblance to the face of one of our primate friends.
The slug feeds on plants and small insects by wrapping around them with two long tentacles at the front of its body.
The monkey slug can be found all over North America, especially in regions with deciduous forests, such as New England and the eastern U.S.
18. Spotted Apatelodes Caterpillar
The spotted apatelodes caterpillar is one of the giant moths in North America, with mature types of caterpillars in Wisconsin reaching up to 2 inches (5 cm) long.
The larvae have pale, cream-colored bodies and two pointed dorsal spines protruding from the thorax. These are not actual spines but thickened and hairy projections called tubercles.
Spotted apatelodes can be found across Canada and most of the United States. They feed on many different types of trees and shrubs but prefer oaks, elms, maples, and birches.
19. Io Caterpillar
The Io caterpillar is one of Wisconsin’s most significant types of caterpillars in Wisconsin, measuring up to three inches long.
This type of caterpillar spends its life with its head on the ground and tucks its body underneath a leaf.
It only leaves its hiding spot when it’s hungry, so it’s common to find them at night. They are reddish-brown with little black spots all over their backs.
