6 Invasive Caterpillars (And What They Turn Into)

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6 Invasive Caterpillars and Their Adult Forms

There are hundreds, if not thousands, of insect species in North America that could be considered invasive, and many of them cause serious damage – think emerald ash borer, japanese beetle, and spotted lanternfly, to name a few. When it comes to butterfly and moth invasive species, there are fewer well-known examples. Some, however, are just as destructive and widespread as those we just mentioned.

This guide identifies 6 invasive butterfly and moth species, and shows you the caterpillar of each species. In addition, for each species listed you will see the following information:

The Basics

• Does it sting?
  
• What does it eat?
  
• Will it seriously damage plants or trees?
  
• Where in North America is it found?
  
• What does it turn into?

Now lets look at some invasive caterpillars, and see what their adult forms look like!

Spongy Moth Caterpillar (Formerly Known as the Gypsy Moth)

The Basics

• Does it sting? No, but the spines can be irritating
  
• What does it eat? Many deciduous trees, especially oaks
  
• Will it seriously damage plants or trees? Yes
• Where in North America is it found? Across the eastern part of the country
• What does it turn into? A brown moth
  

Formerly known as the gypsy moth, the spongy moth has one of the most destructive caterpillars in the world. Originating in Europe, the spongy moth was introduced to North America in 1869 by an amateur entomologist named Etienne Leopold Trouvelot. Neglecting the most basic principles of responsible science, Trouvelot allowed the species to escape and become established on the trees and bushes around his property; from there, it was only a matter of time before the spongy moth spread to nearby forests. Today, this species threatens entire forests across the eastern half of the country!

Large Yellow Underwing Moth

The Basics

• Does it sting? No
  
• What does it eat? Many garden plants
  
• Will it seriously damage plants or trees? If there are enough of them, yes
  
• Where in North America is it found? Mostly in the East, although it is spreading across northern Canada
  
• What does it turn into? A brown moth with yellow hind wings.
  

This fat, gray-brown caterpillar feeds on a wide variety of garden plants. It's one of a group of caterpillars loosely known as "cutworms," many of which are native to North America. The large yellow underwing, however, is a newcomer that only arrived in the 1970's. Since then it has spread with amazing speed across most of the northern half of the country.

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You will often find the robust moth, with its yellow hind wings, fluttering against a porch light on a warm summer night.

Cabbage White Butterfly

The Basics

• Does it sting? No
  
• What does it eat? Cabbages and many other garden plants
• Will it seriously damage plants or trees? Yes
• Where in North America is it found? Literally everywhere
• What does it turn into? A plain white butterfly
  

The imported European cabbage white, as it is often called, is one of history's most successful insect colonizers. There is hardly a field, garden, or yard that doesn't have one or more of these nondescript little butterflies fluttering around, and that goes for nearly every place on earth other than deep forests and mountain tops.

Cabbage white caterpillars are marvels of low-key camouflage; they even have a dense covering of short hairs that off-sets shadow and blurs their contours. They are a precise match for the green of the leaves upon which they feed and rest, which makes finding them very challenging indeed.

European Corn Borer

The Basics

• Does it sting? No
  
• What does it eat? Corn on the cob
  
• Will it seriously damage plants or trees? Yes
  
• Where in North America is it found? Throughout North America
  
• What does it turn into? A small, yellow-brown moth
  

When you open up an ear of corn and the end is rotten, soggy, and infested with worms, you can thank the European corn borer. This species lays eggs on ripening corn, and when the caterpillar hatches out it bores into the ear and starts to eat the kernels on the end. It's hard to tell by looking which corn ears are infested, so it's usually a nasty surprise when you start shucking...

This invasive caterpillar was first reported in Massachusetts around 1920, but it's thought that it was actually in the country several years before that.

Brown-tail Moth

The Basics

• Does it sting? Yes, the spines have a toxin like poison ivy
  
• What does it eat? Many deciduous trees
  
• Will it seriously damage plants or trees? Yes
  
• Where in North America is it found? In the north-east
  
• What does it turn into? A pretty white moth
  

Originally from Europe, the brown-tail moth is a notorious invasive species with a notorious caterpillar. It's not the destruction that it inflicts on North American native trees that's an issue, so much as the deleterious effects of the caterpillar on people who are sensitive to allergens and irritants. The caterpillar possesses barbed, toxic spines that can break loose and become lodged in a person's skin or even lungs; cocoons and dead caterpillars are even worse, since the spines are loose and easily airborne. There have been records, old and not always well documented, of people inhaling enough spines from an infestation of caterpillars to cause serious illness, and even death! Caterpillars shed the hairs, they remain toxic for years, and they can become windblown, so even mowing your lawn or raking leaves can cause a serious health problem.

The innocent-looking white moth lays large batches of eggs on deciduous trees, much like the dreaded spongy moth (above). However, the brown-tail moth and its invasive caterpillar have not become a widespread pest like the spongy moth, thanks largely to the activity of parasitic flies and wasps.

Cynthia Giant Silk Moth

The Basics

• Does it sting? No
  
• What does it eat? Ailanthus (tree of heaven)
  
• Will it seriously damage plants or trees? Not usually
  
• Where in North America is it found? Along the east coast
  
• What does it turn into? A huge, stunning moth
  

The cynthia moth is technically an invasive species, but the caterpillar feeds exclusively on ailanthus (tree of heaven), which is itself an invasive species, so no one is particularly activated by its presence in North America. Add to that its amazing size and beauty, and the cynthia moth is one invasive caterpillar that we can all appreciate!

Thanks for Reading!

And be sure to check out all the other great Greenmind Guides articles!

Resources

The following sources were used for this article:

https://www.nps.gov/isro/learn/nature/invasive-species-gypsy-moth.htm

https://butterfly-conservation.org/moths/large-yellow-underwing

https://wespeoplesfossils.blogs.wesleyan.edu/2018/11/05/conquer-a-familar-foreign-silk-moth/

https://www.forestpests.org/vd/144.html

https://www.dec.ny.gov/animals/83118.html

https://www.frontiersin.org/articles/10.3389/finsc.2021.650520/full

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.