9 Weird (but COMMON) Caterpillars in Arizona (2023)
What kinds of caterpillars can you find in Arizona?
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 Arizona!
Since it would be impossible to list them all in one article, I chose the 9 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 Arizona!
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 Arizona, 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 Arizona! 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 Arizona!
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 Arizona in meadows, open lots, and fields.
The Variegated Fritillary’s chrysalis is the most beautiful of all the caterpillars in Arizona. 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 Arizona.
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. Parsley Caterpillar (Black Swallowtail)
- Papilio polyxenes
- The coloring is bright green, with rings of black and yellow dots down the length of the body.
- The head and thorax are slightly larger than the back, and the legs and pro-legs are pronounced and visible even from a distance.
- Parsley plants are the preferred host of this species.
Parsley Caterpillars, sometimes called parsley worms, are the larva of the Black Swallowtail butterfly. They get their name from their preferred host and favorite snack, the parsley plant.
At first glance, it’s easy to mistake a Parsley Caterpillar for a Monarch. But, the coloring is slightly different, and the stripes on the Monarch Caterpillar are a bit thinner. It would also be unusual for a Monarch Caterpillar to eat parsley or other garden herbs since they eat milkweed almost exclusively!
If you’re a gardener, you might consider Parsley Caterpillars a bit of a nuisance since they can decimate a parsley plant quickly. But, if you plant some extra, you’ll be rewarded with sightings of the beautiful Black Swallowtail butterfly in a few weeks!
#8. Flannel Moth Caterpillar (Asp)
- The coloring is off-white to brown and long, thick hair covers the entire body, making this caterpillar resemble a wig.
- Generally, about 1 inch long and 0.5 inches wide.
- Prefers oak, elm, and wild plum trees as hosts.
If you see a very furry caterpillar in Arizona, STAY BACK!
It’s most likely a member of the Flannel Moth family, the most venomous caterpillars in our area. Victims have described the pain from this caterpillar’s sting as similar to a broken bone or a white-hot burning sensation.
Their sting can cause tons of unpleasant symptoms, including swelling, nausea, headache, chest pain, and difficulty breathing. Especially in young children, the symptoms require medical attention, so if you think you’ve been stung, seek help!
Contact with Flannel Moth Caterpillars often happens during gardening or clearing brush. They use many common yard plants as hosts. You should be extra careful if you have oak or elm trees, roses, or ivy in your yard since these are its favorites. These caterpillars are most common in late spring and summer.
It’s always a good idea to wear gloves if you’re working outside, but especially if you have them in your neighborhood!
Adult Flannel Moths are just as furry as their caterpillars, but they aren’t nearly as painful to touch!
#9. Hubbard’s Silk Moth Caterpillar
- Syssphinx hubbardi
- Coloring is green with a violet stripe along the sides, and white dots speckle the body.
- Thin, hair-like spikes cover the body.
- Honey mesquite and catclaw acacia are this species’ favorite host plants.
This caterpillar has an extraordinary talent – it glows in the dark!
While technically this species displays bio-fluorescence, meaning it glows under UV light, it’s one of the only caterpillars in Arizona that can be compared to a glowstick. 🙂
Look for Hubbard’s Silk Moth Caterpillars on desert plants like Wright’s acacia, honey mesquite, and catclaw acacia. They’re most active in the spring and summer.
Interestingly, this species doesn’t attach their chrysalis to a tree when it comes time to transform into a moth. Instead, it creates a shallow hole in the ground, spins its tough outer shell of silk, and settles in for the winter!
Adult Hubbard’s Silk Moths are much more unassuming than their larva, however, they do hide a bright secret under their wings – the top of the lower wings are bright pink!
Do you need more help identifying caterpillars in Arizona?
Here are some recommended books on Amazon!
Which of these caterpillars have you seen in Arizona?
Leave a comment below!
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About 2 to 2 1/2 inches reddish on most of it’s body. Green head and rear small white dots on girth of most segments. Larger teardrop shaped spots longitudinally that are Silver in color. Actually appear to be metallic. Pairs of red and green horns front and rear. Each silver spot also has a short horn or spine. I have pics if anyone is interested
Catapiller like or worm light in color about an inch in length found infoors