19 Weird (but COMMON) Caterpillars in Utah (2024)

What kinds of caterpillars can you find in Utah?

Common Caterpillars 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 19 most interesting and common ones to share with you. 🙂


#1. Monarch Caterpillar

  • Danaus plexippus

Utah Caterpillars species

Identifying Characteristics:

  • 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!

Common Utah Caterpillars

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!


#2. Cabbageworm

  • Pieris rapae

Identifying Characteristics:

  • 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

Identifying Characteristics:

  • 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

Identifying Characteristics:

  • 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

Identifying Characteristics:

  • 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!


#6. Hornworms

  • Manduca sexta – Tobacco Hornworm
  • Manduca quinquemaculata – Tomato Hornworm

Identifying Characteristics:

  • 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

Identifying Characteristics:

  • 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:


#8. Large Yellow Underwing

  • Noctua pronuba

You’re most likely to find these caterpillars in Utah in open or shrubby areas, but they are habitat generalists that can adapt to various conditions. For example, they’re happy in urban and suburban areas, fields, agricultural areas, yards, and parks.

The adult moths are mostly nocturnal and are attracted to outdoor lights. You may occasionally spot large groups of them around bright lights.

Large Yellow Underwings might not have the most creative name, but it’s certainly accurate! At rest, their brown forewings usually cover their brightly colored hindwings, but you’ll see a flash of color when they take off! This flash helps to confuse and startle would-be predators.

Large Yellow Underwings have a longer lifespan than many other moth species. In captivity, males live an average of 55 days, and females live about 75 days. Despite their long lifespan, they only have one new generation per year.


#9. Painted Lady

  • Vanessa cardui
Vanessa cardui. (2023, August 10). In Wikipedia.
  • The caterpillars’ coloring is variable, ranging from greenish-yellow to charcoal. Most have light-colored spots.

Look for Painted Lady caterpillars in Utah in open areas that are quiet and undisturbed, like roadsides, pastures, and gardens.

The population of Painted Lady’s can drastically differ from year to year. It’s common for them not to be seen for years in some places, then suddenly show up in significant numbers.

The Painted Lady is the only butterfly that mates year-round! Because of its constant migration pattern, it spends its entire life in suitable areas for its eggs to hatch.


#10. Red Admiral

  • Vanessa atalanta

  • The caterpillars are pinkish-gray to charcoal with white spots. They have spines along the back that resemble hairs.

Look for this caterpillar in Utah near the edge of forests in moist habitats.

Red Admiral Butterflies have a unique favorite food – they love fermented fruit! If you’d like to attract them, try placing overripe cut fruit in a sunny spot in your yard.

Red Admirals are migratory butterflies. They fly south toward warmer climates in winter and then move north again in late spring when food is more plentiful.

If you’re looking for a butterfly that’s easy to observe, you’re in luck! Red Admirals are very calm and easy to approach and frequently land on humans!


#11. Spotted Tussock Moth

  • Lophocampa maculata

Spotted Tussock Moths are in the tiger moth family, named for their patterns of alternating dark and light colors. These moths and their caterpillars are what’s known as polymorphic, meaning that they come in many color variations.

You’ll most likely find Spotted Tussock Moth caterpillars in Utah in deciduous forests. Researchers have found that Spotted Tussock Moths have a regional taste for cuisine, just like people! Caterpillars from certain regions often prefer specific tree species.

After about two months of feeding, the caterpillars pupate. They spin brown silk cocoons attached to leaves where they will overwinter, emerging as adults the following spring.


#12. Mourning Cloak

  • Nymphalis Antiopa

  • Caterpillars are black with white specks and a row of red spots on the back.

Mourning Cloak caterpillars are most often found near deciduous forests. However, their habitat includes many developed areas like suburban yards, parks, and golf courses.

You might have a hard time finding this caterpillar in Utah.

Even though it’s fairly widespread, its preference for cold weather and solitary habits make it hard to spot, even for avid butterfly enthusiasts!butterflies in the united states

Mourning Cloaks are often the first butterflies to become active in the spring! In fact, some adults are even active through winter on warm days when snow is still on the ground.

They’re also one of the longest-lived butterflies, with some individuals living up to ten months!


#13. Forest Tent Caterpillar Moth

  • Malacosoma disstria

Forest Tent Caterpillar Moth populations fluctuate in cycles, so you may go years without seeing any and then see lots of them in one season. Their populations reach outbreak proportions every 6-16 years.

Adult Forest Tent Caterpillar Moths are active in July, don’t feed, and live for ten days. Especially in outbreak years, you might spot large groups clustered around outdoor lights.

Unlike other tent caterpillars, Forest Tent Caterpillars don’t spin true tents. Instead, they spin silk mats on the tree’s trunk or branches where they rest when they’re not feeding.


#14. Western Tent Caterpillar Moth

  • Malacosoma californica

In the fall, Western Tent Caterpillar Moths lay about 150 to 250 eggs in oval-shaped masses. They cover the eggs with a gluey cement substance called spumaline, which helps hold in heat and absorbs rainwater to prevent the eggs from drying out. It also protects the eggs from parasitoid wasps.

Even though it only takes three to four weeks for the caterpillars to mature, they must overwinter in this stage before pupating into moths. Their name comes from the silken tent they create to protect themselves from extreme cold during this time.

These caterpillars have a voracious appetite and can quickly defoliate trees in Utah during a population outbreak. While it may be unsightly, the trees usually recover just fine. Interestingly, these caterpillars have regional tastes, and the specific trees they prefer are highly dependent on their location.


#15. Checkered White

  • Pontia Protodice
Pontia protodice. (2023, August 13). In Wikipedia.

Checkered White caterpillars are common in Utah.

One of the most fascinating characteristics of this butterfly is its ability to use UV signals to communicate. These amazing insects can tell the difference between males and females of their species based on the UV radiation they give off! If a female notices that there are a lot of other females, she will migrate to a less dense population in hopes of attracting a mate.

Checkered White Range Map

Pontia protodice. (2023, August 13). In Wikipedia.

Checkered White females lay their eggs on the host plants’ fruits and sometimes the stems. The larvae prefer to eat the flower or fruit of the host plant instead of the leaves.

butterflies in the united states

This butterfly prefers open and sunny areas like deserts and plains, and it’s often found in vacant lots, airports, railroads, and dry grassland.


#16. White-lined Sphinx

  • Hyles lineata

In the spring, the adult females lay hundreds of eggs on host plants. Occasionally, explosive outbreaks of this species occur, and during these times, you might see large groups of caterpillars moving together. They have even been reported to cover entire sections of roadways!

The caterpillars pupate in burrows underground. Pupation takes about two to three weeks, and when they’re close to finished, they wiggle up closer to the surface of the soil before emerging as adult moths.

White-lined Sphinx Moths are sometimes mistaken for hummingbirds. They can rapidly beat their wings to hover at flowers and reach in to sip nectar with their long proboscis. Their favorite flowers include Cardinal Vine, Jimsonweed, Petunia, Phlox, Lilac, Hostas, Honeysuckles, Evening Primroses, and Penstemon.


#17. Queen

  • Danaus Gilippus

Queen caterpillars are found in open and arid areas in Utah close to milkweed. Males have a black scale patch that releases pheromones, attracting females to mate with. After mating, the female will stay close to the area where she found the male and lay her eggs nearby.

Queen butterflies lay eggs on milkweed plants.

butterflies in the united states

The fascinating reason for this comes down to self-preservation! Like other caterpillars, these insects consume Cardiac Glycosides from the milkweed plants. These chemicals taste bad to predators and are carried over to their adult stage, protecting them from being eaten.


#18. Two-Tailed Swallowtail

  • Papilio Multicaudata

Two-Tailed Swallowtail caterpillars are found in Utah in areas with open space and plenty of sunlight. Look for them in foothills, canyons, valleys, woodlands, roadsides, parks, cities, and suburb gardens.

Males of this species spend their entire lives finding a female to mate with due to their short lifespan. If it takes a long time to find a mate, males search for nutrients in rotten material, dirt, and sometimes feces, an odd behavior called mud puddling.

butterflies in the united states

Although it’s one of the most recognizable features, the Two-tailed Swallowtail doesn’t need its tails to fly. Instead, they’re often used to escape predators. When a predator attacks the Swallowtail and grabs onto its tail, it breaks off, allowing the butterfly to escape.


#19. Western Tiger Swallowtail

  • Papilio Rutulus
Papilio rutulus. (2022, January 17). In Wikipedia.

Look for these caterpillars in Utah near water.

Western Tiger Swallowtails prefer being close to rivers, streams, and lakes, and they’re often seen in gardens, roadside meadows, canyons, and parks.

As a deterrent against predators, the caterpillar has two large spots on its tail that look like eyes. They also have a forked organ called a Stinkhorn or Osmeterium, which produces a foul smell to keep predators away.

Western Tiger Swallowtail Range Map

Papilio rutulus. (2022, January 17). In Wikipedia.

To find a mate, males flutter around hilltops or canyons looking for a female. After mating, the female will deposit her eggs on the leaves of a host plant, usually a willow, cottonwood, or aspen tree. When the caterpillars appear, they instinctively seek shelter in the tree’s foliage.

butterflies in the united states


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?

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