Copper Underwing Caterpillar or Humped Green Fruitworm: Identification Guide

In this article, we share information on the copper underwing caterpillar

Do you think of moths as boring, brown insects? Think again. Behind those boring brown wings, you might find bright colors like red and orange! 

Moreover, moths during their larval stage can be brightly colored caterpillars.

The case in point is the Copper Underwing Caterpillar or the Humped Green Fruitworm – a bright green caterpillar. 

Copper Underwing Caterpillar
Source: WanderingMogwaiCC BY-SA 4.0, via Wikimedia Commons

The copper underwing is part of a family of underwing caterpillars, like the large yellow underwing or pink underwing, who all grow into moths with brightly colored underwings.

For example, the Copper underwing caterpillars grow into brown moths that hide bright orange underwings that you only see when they are in flight. 

What Is a Copper Underwing Caterpillar? 

A Copper Underwing Caterpillar is the larval stage of the Copper Underwing moth. Their bodies are blue-green in color, segmented, and can reach a length of 1.10 inches

The moth caterpillar has a queer, pyramidal shape and distinct hump on its rear, through which you can easily identify them. 

There is also a thin line running along the back of their body. 

What Do Copper Underwing Caterpillars Turn Into?

After chrysalis, copper underwing caterpillars turn into brown-colored moths, simply called Copper Underwings. 

Despite its name, the moth actually belongs to the Amphipyrine Sallow family, not the Underwing family. 

Copper Underwing Caterpillar
Source: Beatriz Moisset, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

What Does It Look Like?

Adult moths are dark brown in color. Their wings have specs of lighter shades, with a tan spot at the center of their forewings. 

The hindwings, which are hidden unless in bright light, are a bright, coppery color. 

Visually, it is very similar to other moths of the Underwing family. The latter has a thick dark band instead of specs. 

As a caterpillar, they’re blue-green in color with tiny specs of cream and yellow. 

There is also a yellowish ridge running atop their body with spots on them. The 8th abdominal segment has a raised hump. 

How Big Is a Copper Underwing Caterpillar and Moth? 

The copper underwing moth is larger in size than those belonging to the underwing family. Their wing span can go up to 2.3 inches

The caterpillar or Humped Green Fruitworm ranges in size from 0.9 to 1.1 inches

What Do Copper Underwing Caterpillars Eat?

This pyramidal Green Fruitworm is not at all fussy and can survive on a large range of broadleaf trees (they’re generalist feeders). 

Some common host plants are basswood, rhododendron, willow, oak, birch, and fruits of deciduous trees

Among vines, they feed on raspberry, grape, and Virginia creeper. They have a special affinity towards apples and can sometimes eat rosebuds. 

Copper Underwing Caterpillar

Lifecycle of A Copper Underwing Caterpillar

Adult copper underwings lay eggs on the leaves of deciduous trees. After winter, the eggs hatch into caterpillars that feed on leaves and fruits. 

During this time, they are common prey for birds. Around the end of June, the caterpillars turn into pupae. 

The pupae are dark brown in color. Adult moths emerge towards the end of summer. Currently, very little study has been done on their chrysalis. 

Adult moths are nocturnal and attracted to light. They are also attracted to sugar and sugary substances. You can identify female moths as they are larger in size than males. 

Do They Bite or Sting?

The green fruitworm attacks leaves and fruits. They are commonly kept as pets by children to observe the life cycle of a caterpillar. 

As such, there is no evidence of them biting, stinging, or posing any threat to humans. 

If your garden has an infestation, you can get rid of them by using natural insecticides or sparing water mixed with dish soap. 

Copper Underwing Caterpillar
Source: Donald Hobern from Canberra, AustraliaCC BY 2.0, via Wikimedia Commons

Are They Poisonous or Dangerous?

The bright orange color of the moth leads many to believe that these moths are poisonous. But it is not so. 

All caterpillars and moths belonging to the underwing family (or Noctuidae as the scientific name goes) are non-toxic for predators. 

Sometimes, the scales on some moth species can cause allergies

Do They Infest and Damage Crops?

Copper underwing caterpillars are feeders on leaves and fruits. They can leave round holes in your crops and destroy fruits. 

While they can cause damage and wastage, they are not typically considered pests. 

This is because they are univoltine or capable of only producing one generation per year. Unlike pests that infest and reproduce quickly, copper underwings are a slow-growing insect. 

What Eats Them?

Common predators of the caterpillar are birds, beetles, and wasps. Sometimes, wasps or other insects may lay parasitic eggs on their body so the larvae can feast on the caterpillar after birth. 

The caterpillars hide on the underside of the leaves. They do not have any special defense mechanisms, though the bright color of the moth deters some birds. 

Frequently Asked Questions

Where do copper butterflies live?

Copper underwings are found in the Palaearctic region. This includes the US, southern parts of Canada, North Africa, Korea, and Japan. 
They are quite widespread in this area but do not hang out in large groups. Their ideal habitat is woodlands, shrubbery, and open gardens. 

Is the red underwing moth rare?

The red underwing is a common moth found across multiple continents. In North America, they thrive in California and Arizona as well as in southern Canada. 
In Europe, they’re common in Central and Southern regions as well as England.

How long does a copper butterfly live?

The copper underwing moth has 1 generation every year. Being a larva takes up most of this time as butterflies tend to have a lifespan of a few weeks only. 
Copper butterflies, however, are a completely different species. The adult copper butterfly has a lifespan of only two weeks

What does the caterpillar change into?

The pyramidal green fruitworm eventually changes into a brown-colored moth. Caterpillars usually form pupas just before winter. 
Though sometimes pupae might appear as early as April, depending on the climate. Adult moths emerge around May or June.

Wrap Up 

Non-toxic caterpillars are a great way for kids to observe the life cycle of moths. The Humped Green Fruitworm is very easy to identify due to its unique look and color. 

You will find many of them concentrated in the same region – especially if you have apple trees growing. Thank you for reading!

Reader Emails

Over the years, we have received many communications from our readers trying to ascertain what the green caterpillar in their yard or garden was, especially since they look a little bit like hornworms, which are plant pests.. 

Please read through some of these emails and also admire the variety of pictures of this caterpillar.

Letter 1 – Unknown Hornworm from Korea is Underwing Caterpillar

 

Korean Mystery Caterpillar
May 31, 2010
Dear Bugman (men/women),
I’m a kindergarten teacher in Seoul, South Korea. My walk to work every morning takes me down a mountain (part of the range that drops down into Northern Seoul) and I make it a habit to photograph and (when possible) pick up interesting things for my students on the way. We already have a garden snail in a terrarium in our classroom and he’s been a great success. Just this morning (May 31st) I was walking down the hill as usual and nearly smushed something green. I stopped and found a caterpillar on the road. He’s – hang on, let me measure him – three centimeters long, a beautiful bright green, with a yellow-white lateral stripe on each side, and a white stripe down his back. He has tiny white spots all over except along the lateral lines, where the dots are white inside with a ring of black surrounding. He has a single posterior horn that looks more like a rose thorn than a long thin antler; the horn has white stripes running up to the tip (one following the dorsal st ripe and two on either side for a total of six). He’s got two legs under the horn, then a eight in the middle, and what seem to be six smaller ones under his face. He’s soft and velvety to the touch and completely harmless.
I sure hope that’s a detailed enough description for you. I’d like to keep him in the classroom throughout his metamorphosis if I possibly can, but first of all I have to figure out what kind of plants he likes to eat – so far he’s not been interested in the local greenery I’ve plucked (lilac leaves, leaves from the azaleas that are all over the place, some random other stuff). What IS this little guy? Is he going to do well in a terrarium? And by some miracle, do you know what he’d like to eat?
Thanks a bunch!
Miss Sandra and the Yellow Canary classroom
Bukan-san mountain region, Seoul, South Korea

Copper Underwing Caterpillar

Dear Miss Sandra,
First, we want to say that you sound like a wonderful teacher and that your class is fortunate that you have taken the initiative to teach your charges about the natural world.  Alas, we have struggled unsuccessfully to identify your Hornworm in the family Sphingidae in an effort to identify the food plant.  Hornworms are the caterpillars of Sphinx Moths or Hawkmoths.  They generally pupate underground, and it is possible that this caterpillar left its food plant to search for a good location to dig.  Providing some loose soil in the bottom of the terrariam may encourage him to dig underground to pupate.  Make sure the soil is not too wet nor too dry.  We have been searching the Sphingidae of the Eastern Palaearctic website, China section, in an attempt to identify the species, but China is a big country with many potential species.  Some moths pictured do not have images of caterpillars, and with some species, the life cycles and early stages are unknown.  Hopefully, one of our readers will be able to identify your species so that you can provide the necessary food.  The horn on your specimen is very unusual looking and should be able to provide a unique characteristic for identification purposes.

Copper Underwing Caterpillar

Correction thanks to Karl:  Underwing Caterpillar
June 1, 2010
Hi Daniel and Miss Sandra:
The unusual “horn” is actually more of a hump, and this caterpillar is an underwing moth (Noctuidae) not a hornworm (Sphingidae). It looks like a Copper Underwing (Amphipyra pyramidae) – other common names include Humped Green Fruitworm and Pyramidal Green Fruitworm. It’s a Palearctic species with a very wide distribution, including all of Europe and across central Eurasia to Korea and Japan, and the higher altitude regions of from North Africa to the northern Indian subcontinent. It appears to be present across North America as well but I suspect it has been introduced to that continent. There is an abundance of images on the internet (additional links below). A related species, A. perflua, has a similar distribution, including Korea, but I wasn’t able to find any images for comparison.
http://www.pbase.com/spjaffe/image/113128207
http://www.leps.it/indexjs.htm?SpeciesPages/AmphiPyram.htm
Karl

Dear Karl and Daniel,
Thank you so much for your information and assistance!  We had a great time in class looking at pictures of what our little friend will turn into.  We would have loved to watch his metamorphosis, but as we couldn’t entice him to enjoy any of our plant offerings, we let him go in our garden in the hopes that he would find his own way to something delicious.  You were all incredibly helpful – never have there been a group of five year olds so in love with bugs as my students, let me tell you.  I’ll be sure to take pictures of any copper underwings I run across!
Thanks again!
Sandra

Letter 2 – Copper Underwing Caterpillar

 

Subject: Mystery Chubby Yellow and Green Caterpillar on Oak
Location: Southern Illinois
May 16, 2013 4:39 pm
I’m usually pretty good at larger and cuter caterpillar identification, but I’m stuck on this one. It is pretty early in the season, only been decent caterpillar-growing weather for the last two weeks or so. About an inch long on an oak tree. Suspect he has some more growing to do.
Signature: -Bert

Copper Underwing Caterpillar
Copper Underwing Caterpillar

Hi Bert,
We found a nearly identical image posted to BugGuide where this is identified as a Copper Underwing Caterpillar,
Amphipyra pyramidoides.  The caterpillar is also called a Humped Green Fruitworm or Pyramidal Fruitworm, and BugGuide indicates:  “larvae are general feeders on leaves of many broadleaf trees and shrubs, including apple, basswood, hawthorn, maple, oak, walnut, raspberry, grape, greenbrier.”  Despite the name, this is not a true Underwing Moth which are in the genus Catocala.

Thanks very much. I thought it was much younger than it was, turns out they overwinter as eggs, so they get quite a jump on spring, and that one was nearly full-sized. Somewhat disappointed to see the adults are not very eye catching.

Letter 3 – Humped Green Fruitworm

 

Subject: caterpillar
Location: bluffs of lacrosse wi
June 7, 2015 9:04 pm
Found this guy munching on some leaves on a late night hike (around 2 am) on a trail going up miller bluff in lacrosse wi
Signature: Zach g

Humped Green Fruitworm
Humped Green Fruitworm

Dear Zach,
Our first thought was that this might be a Prominent Moth Caterpillar, but searching BugGuide did not produce any visual matches.  We next started going through Owlet Moth Caterpillars on BugGuide and it was there we found matching images of the Humped Green Fruitworm, the larva of the Copper Underwing,
Amphipyra pyramidoides.  According to BugGuide:  “larvae are general feeders on leaves of many broadleaf trees and shrubs, including apple, basswood, hawthorn, maple, oak, walnut, raspberry, grape, greenbrier (Smilax).”

Letter 4 – Humped Green Fruitworm

 

Subject: green caterpillar feeding on Azalea
Location: Minneapolis, MN
May 28, 2016 8:48 am
This morning while picking off azalea sawflies, I found this caterpillar on my “Northern Lights”
azalea . In 15 years of springtime sawfly activity I have never seen a caterpillar like this; on or off an azalea! If you could ID this I would be very grateful.
Signature: Joanne K., Minneapolis

Humped Green Fruitworm
Humped Green Fruitworm

Dear Joanne,
Your distinctive caterpillar belongs to the Copper Underwing,
Amphipyra pyramidoides, and it is sometimes called a Humped Green Fruitworm, according to BugGuide.  According to BugGuide:  “Larvae are general feeders on leaves of many broadleaf trees and shrubs, including apple, basswood, hawthorn, maple, oak, walnut, raspberry, viburnum, grape, greenbrier (Smilax)” and thanks to your submission, our readers will know to also search for them feeding on Azalea.

Gosh, that was quick!
Thanks so much, he is quite beautiful.
Thanks again.
Joanne K

Letter 5 – Humped Green Fruitworm

 

Subject: Possible Silkworm or Hornworm?
Location: Marquette, MI
June 23, 2016 5:03 pm
I had come across a very plump caterpillar when letting my dogs outside. It was on a beach tree, and looked to be in the process of forming a chrysalis, as it was hanging upside-down. It was/ is approximately between 1- 2 long, and is green. It’s face is also green, and has: a continuous white stripe on each side of its body; yellow dashes on it’s back; and three prominent yellow dashed lines going down it’s back. It does have a tail, and has an end that looks similar to a tail-less Silkworm and/ or Hornworm. Overall, this Caterpillar seems to have a build similar to a Silkworm and Hornworm.
I live in Michigan’s Upper Peninsula, which mostly consists of rain forests, and is surrounded by Lake Superior, Lake Michigan, and Lake Huron. Because of these factors, we get a lot of bugs
Signature: – Sam

Humped Green Fruitworm
Humped Green Fruitworm

Dear Sam,
This is neither a Silkworm nor a Hornworm.  This is a Humped Green Fruitworm, the larva of the Copper Underwing,
Amphipyra pyramidoides.

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

    View all posts

2 thoughts on “Copper Underwing Caterpillar or Humped Green Fruitworm: Identification Guide”

Leave a Comment