7 Weird (but COMMON) Caterpillars in Utah (2023)
What kinds of caterpillars can you find in Utah?
Caterpillars are some of the MOST fascinating insects in the world! It always amazes me that caterpillars eventually turn into butterflies or moths.
There are hundreds of different caterpillar species found in Utah!
Since it would be impossible to list them all in one article, I chose the 7 most interesting and common ones to share with you. 🙂
#1. Monarch Caterpillar
- Danaus plexippus
- This famous caterpillar is plump with black, white, and yellow bands.
- Its legs and pro-legs are pronounced, and each end of its body has spindly black tentacles.
- The Monarch’s preferred host plant is milkweed.
Like the adult butterfly, the Monarch is one of the most well-recognized caterpillars in Utah!
Their distinctive stripes and tentacles make them look cartoonish. But this highly visible coloring sends a message to predators: Back Off!
Monarch Caterpillars are toxic to most animals, and at the very least, taste bad! This poison comes from their diet, which is almost entirely made up of milkweed. Toxins from the milkweed plant stay in the caterpillar, producing a bitter taste and poisonous effects.
If you have milkweed in your yard or nearby, your chance of finding Monarch Caterpillars is excellent! Honestly, there is nothing more fun than finding these colorful insects on our milkweed plants and getting to watch them transform into adults!
- Coloring is light green with small yellow dots along the sides.
- This species is small and relatively thin and appears velvety.
- Cabbageworms’ host plants are Brassicas, including cabbage, kale, broccoli, and chard.
In Utah, this species is often called the Imported Cabbageworm because it isn’t native to North America. It was introduced in shipments of cabbage and other brassica plants and soon became an invasive species.
Cabbageworms are considered agricultural pests and can do severe damage to crops to their host plants. Cabbage, brussels sprouts, broccoli, and cauliflower are all susceptible to damage. For a home gardener, the best way to deal with Cabbageworms is to prevent a large infestation. Plant covers, regular weeding, and varied plantings can all help with preventing this hungry invader!
One reason Cabbageworms are so damaging is that they are voracious eaters! They can easily skeletonize entire plants, eating everything but the toughest stems and midveins. Boring through heads of cabbage and making huge dents in broccoli are no problem for this Very Hungry Caterpillar!
Cabbageworms grow into Cabbage White Butterflies, which are one of the most abundant butterflies in Utah! If you see a white butterfly in the spring, chances are it’s a Cabbage White!
#3. Woolly Bear
- Pyrrharctia isabella
- Coloring is black with a wide rusty-red band in the middle.
- As its name suggests, the Woolly Bear caterpillar is covered in dense, coarse hairs.
- Transform into Isabella Tiger Moths.
- Woolly Bears are generalist feeders, meaning they will live on and eat nearly any plant!
As a kid, I can remember hearing tons of stories about Woolly Bear caterpillars – and the coolest part about them is that most of the stories are true! One myth you might have heard is that Woolly Bears can predict the type of winter we’ll have. Unfortunately, this one isn’t true. But there’s plenty of other interesting facts about this cute little caterpillar!
The most fascinating thing about Woolly Bears is the way they hibernate.
That’s to say, they don’t hibernate at all! Instead of burrowing or pupating to escape the cold, Woolly Bears allow themselves to freeze solid. They have a unique chemical in their blood that allows them to thaw out and continue in the spring as if nothing happened!
You may have heard that Woolly Bear Caterpillars are venomous, but this isn’t entirely true. Their hairs don’t contain any toxins or irritants, but some people are sensitive to the hairs and may get a slight rash if they touch one. It’s best to observe the species without touching them, just in case.
Woolly Bear Caterpillars and their adult-form, Isabella Tiger Moths, are found in incredibly varied climates, even the Arctic! Because they will eat almost anything, including herbs, tree leaves, and grasses, they can be found pretty much anywhere plants are growing. Look for them in groups near the base of plants.
Just don’t expect them to take over for your meteorologist! 🙂
#4. Viceroy Caterpillar
- Limenitis archippus
- The coloring is mottled brown or green and white to resemble bird droppings.
- Two dark-colored horns on the head and small spines on the body.
- The chrysalis also resembles bird droppings hanging from a tree branch.
- The preferred host plants of Viceroy Caterpillars are willow, poplar, and cottonwood trees.
Viceroy Caterpillars are one of the ugliest caterpillars in northeastern Utah!
This is by design; their lumpy, mottled appearance makes them look like bird droppings, warding off predators!
Interestingly, this isn’t the Viceroy’s only protection against predators. Viceroy Caterpillars eat plants that are rich in salicylic acid, which they store in their bodies. When predators try to eat them, they are rewarded with a strong, bitter flavor and an upset stomach. One taste and they learn to stay away!
Viceroy Caterpillars primarily live in open forests or fields, and they’re found across many different climates. Look for them during spring and summer, which is when the adults typically mate.
Interestingly, Viceroy and Monarch Caterpillars look almost identical.
#5. Variegated Fritillary Caterpillar
- Euptoieta claudia
- Stripes of black, red, and white run the length of the body.
- Black branched spines stick out from each body segment in even rows.
- Variegated Fritillaries will use any plant in the violet or alder family as a host plant. These include common blue violets, yellow alder, and pansies.
Variegated Fritillary Caterpillars share the same name as their adult-form butterflies. They eat ornamental plants like violets, pansies, and passionflower.
Look for these caterpillars in Utah in meadows, open lots, and fields.
The Variegated Fritillary’s chrysalis is the most beautiful of all the caterpillars in Utah. This protective shell is where the caterpillar transforms into the adult butterfly. Its pearly white color and shiny gold spikes make it look like an expensive jeweled pendant!
- Manduca sexta – Tobacco Hornworm
- Manduca quinquemaculata – Tomato Hornworm
- These two species have nearly identical coloring: bright green with tiny white lines and black dots.
- There’s a thin, filament-like “horn” on the rear end.
- Hornworms grow up to 3.5 inches in length before metamorphosis.
Tobacco and Tomato Hornworms are so similar that they’re often mistaken for one another! The easiest way to tell them apart is by the color of their horns. Tobacco Hornworms have a red horn, and Tomato Hornworms have a green or black horn. While the adult moths they grow into aren’t quite as similar, they do have the same coloring.
Hornworms are considered one of the most destructive caterpillars in Utah.
They specialize in eating tobacco, tomato, and other similar plants and regularly cause problems for farms and growers who don’t use pesticides. However, relocating or killing the caterpillars can be enough for many home gardeners to deter any more from eating your plants.
One particularly disgusting enemy of the hornworm is Cotesia congregata. It’s a parasitoid wasp that attacks the caterpillar with venom and then lays its eggs INSIDE the living body. As the caterpillar matures, so do the wasp eggs, slowly feeding on the hornworm until it dies and the wasps hatch. Gross!
#7. Io Caterpillar
- Automeris io
- The coloring is green with two stripes along each side, one red and one white.
- Tufts of short green spines cover the body, with patches of light green showing through.
- Io Caterpillars use hackberry and willow trees as host plants.
Io Caterpillars are highly venomous, and their sting is excruciating!
Fortunately, the sting is rarely severe enough to seek medical attention. Instead, most experts recommend removing the spines with scotch tape, then applying ice to the sting. Over-the-counter antihistamines and pain relievers can also help.
Of course, the best way to stay safe is to avoid touching Io Caterpillars. Since they’re so recognizable, this should be pretty easy!
Their tufts of green spines are distinctive and hard to miss against darker green leaves or brown bark. The red and white stripes on the sides are also helpful – they clearly say, “Stay back, I’m dangerous!”
If you know you’re going to be gardening or doing yard work in an area with Io Moths or their caterpillars, it’s a good idea to wear a hat and gloves. That way, if you happen to brush against one, you won’t have to worry about exposed skin!
Adult Io Moths are just as distinctive as their larva – if not more so! They have a beautiful pattern with large, prominent eyespots. There are two color morphs:
Do you need more help identifying caterpillars in Utah?
Here are some recommended books on Amazon!
Which of these caterpillars have you seen in Utah?
Leave a comment below!
If you enjoy this article, make sure to check out these other guides!