4 Weird (but COMMON) Caterpillars in Idaho (2023)
What kinds of caterpillars can you find in Idaho?
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 Idaho!
Since it would be impossible to list them all in one article, I chose the 4 most interesting and common ones to share with you. 🙂
#1. Monarch Caterpillar
- Danaus plexippus
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 Idaho!
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 Idaho, 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 Idaho! 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 southern Idaho!
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.
Do you need more help identifying caterpillars in Idaho?
Here are some recommended books on Amazon!
Which of these caterpillars have you seen in Idaho?
Leave a comment below!
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