Heres a little warning from someone (me) who saw a family member (my son) find out the hard way about these little guys, and whos kept an eye out for them ever since then.
Its a Tussock Moth Caterpillar, and its venomous. Not the “well, its been nice knowing you” type of venomous, but as my son recently found out, its a pretty unpleasant experience.
He got an up-close-and-personal visit from one, and I think its safe to say hes hoping that it never happens again, and wed really hate to see it happen to you.
As a longtime resident of Illinois, I’ve always been fascinated by the diversity of caterpillars that can be found in the state. From vibrant Monarch caterpillars to fuzzy Woolly Bears these insects go through an incredible metamorphosis as they transform into moths and butterflies. In this article I’ll provide an overview of some of the most common caterpillars in Illinois, including key identification features, preferred host plants, and interesting facts.
Popular Caterpillars in Illinois
Monarch Caterpillar
The Monarch caterpillar is arguably the most famous caterpillar in North America. With its striking black, yellow, and white bands, this caterpillar is easy to identify as it munches on milkweed plants. Monarchs are unique in that they migrate long distances, traveling from Canada and the United States to overwinter in Mexico. In fact, Monarch butterflies are the state insect of Illinois.
Black Swallowtail Caterpillar
Black Swallowtail caterpillars are fans of carrots and other plants in the parsley family. They are black with white dots in their early stages eventually turning green with black bands and yellow dots in later instars. An interesting feature is the orange forked organ called the osmeterium that emerges from behind the head when threatened.
Woolly Bear Caterpillar
The Woolly Bear caterpillar is a fuzzy species covered in stiff bristles It overwinters as a caterpillar, emerging in spring to feed on herbs, grasses, and other low-growing plants A fun folktale suggests that the width of the rusty brown band predicts the severity of upcoming winter weather.
Eastern Tiger Swallowtail Caterpillar
Named for the tiger-like eyespots on its head, the Eastern Tiger Swallowtail caterpillar can be found munching on cherry, tulip, ash, and other tree leaves. It has an intriguing habit of using silk to fold a leaf over itself for protection while resting. The caterpillar changes color as it develops, starting out brown before eventually turning green.
Milkweed Tussock Moth Caterpillar
One look at this colorful caterpillar explains where the name comes from – the milkweed tussock moth caterpillar is covered in vibrant hairs! An older larva may have black, white, yellow, and brown hairs. Interestingly, this species absorbs bitter toxins from milkweed plants, making them unappetizing to potential predators.
Identifying Caterpillars in Illinois
When trying to identify caterpillars, there are some key features to look for:
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Coloration: The colors and patterns can offer clues about the species. For instance, Woolly Bear caterpillars have a rusty band across black ends.
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Host plant: Note whether the caterpillar is feasting on a tree, garden plants, or weeds. Monarchs only eat milkweed, while Black Swallowtails prefer plants in the carrot family.
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Size: Some caterpillars grow much larger than others. Polyphemus moth caterpillars can reach 4 inches long compared to only 1 inch for Red Admiral caterpillars.
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Distinct markings: Many species have unique features like the orange osmeterium of Black Swallowtails or the eyespots on Eastern Tiger Swallowtails.
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Defenses: Warning coloration, toxic hairs, mimicry, and behaviors like thrashing may point to certain groups of caterpillars.
With close observation and by recording key characteristics, even backyard caterpillar enthusiasts can hone their identification skills. Resources like field guides,nature center programs, and online sites can further aid in putting a name to caterpillars.
Caterpillar Habitats Around Illinois
From bustling Chicago to the sprawling Shawnee National Forest, Illinois provides diverse ecosystems where caterpillars can thrive. Here are some hotspots for finding caterpillars in the state:
Prairie Preserves: Native wildflowers like milkweed and asters attract many species to open grasslands. Painted Lady, Monarch, and Skipper caterpillars may be discovered.
Deciduous Forests: Oaks, maples, cherries, and other trees in hardwood forests are chewed by Eastern Tiger Swallowtail, Polyphemus Moth, and other caterpillars. Search leaf undersides!
Backyards: Don’t overlook neighborhood greenspaces! Look for cabbage worms on cole crops or Hummingbird Clearwing Moth caterpillars on honeysuckle.
Marshes: Cattails, sedges, and willows around wetlands host Viceroy, Buckeye, and other moisture-loving larvae.
Milkweed Patches: Find stripes of Monarch caterpillars along roads or ditches where milkweeds flourish. Other species like the Milkweed Tussock Moth also frequent these stands.
Fun Facts About Illinois Caterpillars
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The hickory horned devil is Illinois’ largest caterpillar, reaching 6 inches long! Despite intimidating looks, it is harmless.
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Luna Moth caterpillars in Illinois change drastically as they grow, shifting from green to red.
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Male giant silkworm moths lack mouths and live only to mate after emerging from cocoons. Females are flightless and have small wings.
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Some swallowtail butterflies overwinter as chrysalises, hanging from twigs and resembling small tree buds until spring.
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Woolly Bear caterpillars can survive freezing temperatures by producing a cryoprotectant fluid that acts like antifreeze!
Enjoy the Caterpillar Life Cycle in Illinois
As a caterpillar lover who looks forward to spring hatchlings and summer larvae, I encourage Illinois residents to take advantage of the amazing diversity of caterpillars in our state. Grab a field guide, explore various habitats, and see how many species can be discovered right in your own backyard. Enjoy witnessing the complete metamorphosis of these critters into remarkable moths and butterflies. With so many unique caterpillars calling Illinois home, there’s a fascinating world of hornworms, inchworms, cutworms, and tent caterpillars waiting to be found!
All It Takes Is Just A Single Touch To Make You Totally Regret Meeting One
It was a White-Marked Tussock Moth Caterpillar. I knew that because Id recently read a piece online about venomous caterpillars. I read that piece because wed seen another one crawling on some backyard flowers about a week before.
The caterpillar has a built-in defense mechanism located in those tufts of hair. The venom contained in those hairs is released when the hairs become embedded in your skin upon contact. That venom can cause anything from a minor irritation to a very nasty (but not life-threatening) allergic reaction.
I assumed that because there were two touches involved (where the caterpillar was crawling on his neck, and on his hand when he swept it away) my son would have two areas that would need quick attention. I went straight to Google to see what we needed to do to mitigate the consequences of it being on his skin.
Strangely enough, the caterpillar only nailed him on one of those spots. His neck:Amy Jacobsen, Townsquare Medialoading…
We also found it odd that initially, he showed no signs whatsoever of having been exposed to the venom. However, when it did announce itself, it brought some serious itching, burning, and overall discomfort.
What you see above didnt show up for several hours, and by the time we photographed his neck it was looking a lot better than it did at first. We treated it with ice and calamine lotion, and he seems to be healing up quickly.
By the way, the Tussock Moth Caterpillar is not the only Illinois caterpillar that can cause you pain and discomfort if you touch one. Make sure you dont touch these guys, either:
The Io Moth Caterpillar has stinging hair and barbs that can cause pain and rashes if touched.
The Imperial Moth Caterpillar is covered with irritating hairs that can cause severe itch and rashes.
The Saddleback Caterpillar features stinging spines and hairs that can cause extreme skin irritation.
These Little Creatures May Look Fuzzy And Friendly, But Only The “Fuzzy” Part Is Accurate
Fuzzy, yes. Harmless, not so much. This whole experience began with my son Spencer and I sitting on the patio at home, about to go in and have lunch.
As he stood up, his hand went to the back right-side of his neck and he swept something away that had been crawling on him. When I looked down to see what hed knocked to the ground, I saw an unusual looking caterpillar.
Heres the culprit (right before being terminated with extreme prejudice by an angry mom protecting her grown son):Amy Jacobsen, Townsquare Medialoading…Amy Jacobsen, Townsquare Medialoading…
Insects of Illinois
FAQ
Are there any poisonous caterpillars in Illinois?
The Io Moth Caterpillar has stinging hair and barbs that can cause pain and rashes if touched. The Imperial Moth Caterpillar is covered with irritating hairs that can cause severe itch and rashes.
How do I find out what kind of caterpillar I have?
Look for distinct physical features if the caterpillar has any. Check to see if the caterpillar has a curled tail, head horns, knobs, lashes, spines, or a split tail. These can all be good indicators for certain caterpillar species and will help you narrow down your search rather quickly.
What are the black and brown caterpillars in Illinois?
There are several species of caterpillar that are commonly called “woolly worms”. The woolly worms that are at the center of the winter forecasting legend are black at each end with a reddish-brown band in the middle.
What is a fuzzy yellow caterpillar in Illinois?
American dagger moth larvae are white or yellow hairy caterpillars that look somewhat like woollybears, reaching 2 inches when fully grown.