Are Large Yellow Underwing Caterpillar Poisonous?

Large yellow underwing moths are beautiful creatures with bright, flashy wings but are large yellow underwing caterpillar poisonous? Should you let them sit on your plants? Let’s find out.

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Notorious for the damage they cause to plants, caterpillars are a nuisance you should tend to immediately if they are in your garden.

Some caterpillar species are also poisonous or venomous; hence, their bite can be dangerous to humans.

If you recently came across yellow underwing caterpillars (cutworms) in your garden, you might wonder whether these are harmful to you.

Although cutworms can harm your garden, they aren’t poisonous to humans. Let’s learn more about these bugs.

Are Large Yellow Underwing Caterpillar Poisonous

What Is This Bug?

As you might guess from the name, these are the larvae of large yellow underwing moths. The moth is a species of the Noctuidae family.

Noctua is the Latin word for owlets, and moths of this family are also known as owlet worms.

Several caterpillars of the Noctuidae family are commonly known as cutworms, and so are large yellow underwing caterpillars.

They are called so because of their habit of cutting down seedlings by chewing through the stem of the plant.

What Does It Look Like?

Here is a quick overview of their appearance in different stages of their lives:

Eggs

Large yellow underwing moths lay spherical eggs in large clusters under leaves or areas with overgrowth. These eggs are initially pale yellow but darken a little as they get old.

Larvae

The larvae which you have seen before coming to this article are usually yellow, green, or brown and grow up to around an inch.

They have soft bodies, often with dashes, semicircles, or longitudinal stripes on them.

Adults

Adults are particularly famous for their flashy wings. These nocturnal moths have bright yellow hindwings hidden under large brown or reddish-brown forewings.

The yellow wings have a black band at the bottom, while the brown ones at the front have a black dot near the edge.

The hind wings also have orange, pink, or white stripes on them sometimes. The forewings of the moth are long, narrow, and rounded.

Darker moths of this species also have a pale streak running along the costa.

Where Does It Live?

Although this heavy moth species has become quite common in North America, they aren’t native to these lands.

These moths are very common in the Palearctic region but have spread their little wings to many other places in the world. You might find them all over Central Asia, Europe, North Africa, and the Middle East.

The cutworm moth was introduced to North America in 1979 when it arrived in Nova Scotia. Later it showed up in Michigan in 1998 and Oregon in 2001.

Today, you can find these moths in states like Pennsylvania, Colorado, Vermont, Massachusetts, North Carolina, Wyoming, North Hampshire, British Columbia, California, Connecticut, and Alaska.

Common habitats of this species include grasslands, farmlands, wetlands, moorlands, etc. They prefer to live amidst grass and the base of trees.

Does the Caterpillar Bite?

Now let’s come to an important query: do they bite? Thankfully, large yellow underwing caterpillars neither bite nor sting. They simply curl into a C-shape when disturbed.

Is it poisonous or venomous?

As mentioned in the beginning, some caterpillar species are poisonous, which makes them unsafe to handle.

However, this isn’t an issue with the large yellow underwing caterpillars. They are not poisonous or venomous to humans and do not pose a threat.

Do the adult moths bite?

Like most adult moths, this species of moth doesn’t bite either. They simply don’t have the mouthparts necessary for biting.

Having these brown moths in your garden is a good thing because they are excellent pollinators.

Does It Damage Crops?

While the adult moth rarely damages crops, the caterpillar is a pest. It can cause significant damage by chewing and feeding on leaves, branches, and stems.

Cutworm infestations can defoliate entire plants. As mentioned earlier, the pest is particularly notorious for destroying seedlings by cutting the stems at or below the surface of the soil, thus destroying them completely.

It can also leave behind droppings and stripped leaves. These caterpillars often attack herbs, ornamentals, and vegetable plants like Alliums.

If you have observed several of these caterpillars in your garden, you should quickly go about removing them.

Controlling Cutworms

Cutworms can be a huge menace to your garden, so here is what you should do in order to keep these caterpillars out.

Biological Control

Large yellow underwing caterpillars are prey to a host of natural enemies such as birds, rodents, frogs, spiders, flies, and parasitic wasps.

One of the easiest ways is to introduce beneficial wasps of the Braconidae, Tachinidae Ichneumonidae, and Eulophidae families into your garden.

Trim Regularly

Cutworms like unkempt and overgrown plants, so keep your plants trimmed and remove the mulch regularly from your plants.

Water Your Plants

Keep your plants well watered. These caterpillars don’t like to be in places that have a lot of moisture, so this can make the environment unfavorable to them.

If you find cutworms on your food crops, the caterpillar might become visible under the soil when you are tilling it. You should move them to some other place (preferably somewhere the birds can see them!).

Natural Methods of Removal

You can always pick them off one by one from the leaves. They don’t bite, and you can easily crush their heads to finish them off.

Diatomaceous earth (DE) is an effective natural remedy against these bugs. Just spread a little bit around the stems of the plants and on the perimeters of your garden.

Protecting the Plants

You can put up insect-repellant mesh to cover the vegetable crops. If you have seedlings, you can cover them with plastic.

Organic Pesticides

Bacillus thuringiensis (BT) are effective against cutworms. You can buy them from the market and water them in the soil under the plants.

Nematodes are also predators of cutworms. You can add these to the soil while watering and keep the temperatures between 53-68F.

Frequently Asked Questions

What do yellow underwing caterpillars eat?

Yellow underwing caterpillars mostly feed on herbaceous plants, foliage, ornamental plants, and grasses.
They often snip off the seedlings from the stems, which is where they get their name from.
They have a voracious appetite and can cause a great deal of damage to gardens and crops with their feeding habit.

What does an underwing caterpillar turn into?

As the name suggests, the underwing caterpillar turns into an underwing moth. It takes about a month for the larvae to turn into moths.
Unlike overwintering moths, underwing caterpillars emerge from eggs during spring. They spend their larval stages during the spring and emerge as moths.

How big is a large yellow underwing?

This species of moth is of medium size, with a wingspan of 1.9 to 2.4 inches.
Large yellow underwing moths grow up to a length of 1.8 to 2.2 inches.
While moths of such size shouldn’t be very hard to notice, their color camouflages them well.

How do you get rid of big yellow Underwings?

Natural predators like spiders, parasitic wasps, birds, and rodents can help you get rid of underwings by preying on them.
You can make your vegetable patches unattractive to these caterpillars by keeping them well-irrigated and tidy, clean of plant debris.
If you are dealing with a cutworm infestation, you can use diatomaceous earth and beneficial nematodes to eliminate them.

Is the large yellow underwing invasive?

Yes, although the large yellow underwing is now very common in North America, it’s an invasive species that originated in Europe.
It reached North America in 1979, after which it spread quite far and wide across the continent.

What happens when underwing moths open their wings?

They often open their wings to fly when they see a predator around. It is believed that the flash of bright color distracts their enemies and gives them an extra second or two to fly away.
When their wings are closed, underwing moths blend into their surroundings very well.
They can camouflage especially well when resting on the bark of trees. These moths specifically tend to choose trees against which they can blend properly.

Wrapping up

You don’t have to worry about large yellow underwing caterpillars. They aren’t poisonous, venomous, biters, or stingers.

However, if you find them in your garden, you should keep track of their numbers. They can quickly defoliate your plants, so get rid of them if their population starts to grow.

Keep a look out for these and other potentially harmful caterpillars, such as those of the Pug Moth – Eupithecia spp.

Maintaining a healthy number of natural predators in your garden should help you keep such caterpillars in check without having to use pesticides.

Hopefully, you can now protect your garden from these plant-chewing caterpillars. Thank you for reading!

Reader Emails

Underwing caterpillars look quite nasty, and they have sent many a reader running our way trying to find out if these bugs are poisonous or harmful.

Read the emails below to get a taste of their experiences.

Letter 1 – Underwing Caterpillar, we believe

Caterpillar Location: Edward’s Plateau, Ft. Hood, TX June 4, 2011 1:34 am Hello, I found this caterpillar a few weeks ago on Ashe Juniper, it blended in so well with the branch it was on, it could barely be seen. While the top was non-descript, the underneath of the caterpillar was an odd light seafoam green with darker green spots (see picture). I’ve found some similar looking caterpillars, but nothing that fits, nor mentions a green underside. Any help would be appreciated! Thank you! Signature: writerwren

catocala_cat_juniper_writerwren — possibly Underwing Caterpillar

Dear writerwren, We believe this caterpillar resembles those of the Underwing Moths in the genus Catocala. There are many similar photos on BugGuide, including this view of a Caterpillar underside that has the coloration of your specimen. We find the fact that it was feeding on Ashe Juniper interesting because BugGuide indicates: “Larvae of most species feed on foliage of deciduous trees.” Most Underwing Moths have mottled brown upper wings that blend in with the bark of trees that they rest upon, very effectively camouflaging them from predators. The underwings are often brightly colored with red and black stripes giving the genus its popular name Underwing Moths. The underwings only show when the moth is in flight. Predators will continue to search for the bright coloration when the moth comes to rest and they may fail to notice the camouflaged moth. We tried a web search of the words “catocala, juniper, Texas” and found this technical article, and somewhere buried in it you may find a species that feeds on juniper. We will be out of the office for a week in mid June, and we are preparing your request to go live on June 13.

catocala_cat_writerwren_2 — *Probably Underwing Caterpillar*

Letter 2 – Underwing Caterpillar

Subject: WTH is this? Location: NW Indiana May 17, 2014 7:41 pm Hello, Mr. Bugman: This creature was in my garden yesterday, Friday, May 16, 2014. I live in NW Indiana, Zone 5. Can you ID it, please? I’ve never seen anything like it. It looks like a baby Godzilla. It’s about two inches long. I couldn’t get a clearer picture – sorry. Thank you for your time. Signature: Sincerely, Mary Ann Sumner

Dear Mary Ann, In our opinion, this is an Underwing Caterpillar from the genus Catocala and you can see an image on BugGuide that looks very similar.

Letter 3 – Underwing Caterpillar, perhaps

Subject: Identification request Location: North central Florida, USA May 5, 2015 5:18 am Are you able to identify this caterpillar for me? I think they are dropping out of our pecan trees. They are about 3 inches long. I am located in north central Florida. Thank you for any help you can provide. Signature: Janet

Dear Janet, We believe this might be the Caterpillar of an Underwing Moth in the genus Catocala. According to Entoweb.OKstate: “Pecan catocala commonly feed on pecan, hickory, and other trees.”

Letter 4 – Underwing Caterpillar from Canada

Subject: caterpillar Location: Niagara-On-The-Lake, Ontario June 5, 2015 5:15 pm My husband found this gem in his roofing pouch, wondered if it came off the walnut tree and what kind it is. Underwing perhaps? Signature: me

This is the Caterpillar of an Underwing Moth in the genus Catocala. Underwing Moths get their common name from the brightly colored underwings that flash while the moth is in flight, but are concealed beneath bark patterned forewings that act as camouflage when the Underwing Moth is at rest. We are postdating your submission to go live during our absence from the office in mid-June.

Letter 5 – Underwing Caterpillar, we believe

Subject: What kind of caterpillar? Geographic location of the bug: In Calgary, Alberta on a mat in truck Date: 07/09/2018 Time: 02:06 AM EDT Your letter to the bugman: Hey there, just curious what kind if caterpillar this is? It was found on a mat. Underneath is same color but each “section” has a brown-orange spot. I tried to get it onto a leaf to get it outside and it was like a ninja doing backflips and freaking out! Never seen a caterpillar move that fast! Thanks! How you want your letter signed: K Hunter

Dear K Hunter, This looks to us like an Underwing Caterpillar in the genus Catocala. Here is a BugGuide image for comparison.

Letter 6 – Underwing Caterpillar, we believe

Subject: What is this guy? Geographic location of the bug: Raleigh NC Date: 04/15/2021 Time: 06:38 PM EDT Your letter to the bugman: Found this odd critter on my back porch. About 3” long, relatively flat. Would love to get him to the correct habitat and what he will become. How you want your letter signed: Lisa & Doug

Dear Lisa & Doug, We believe this is an Underwing Caterpillar in the genus Catocala, but we haven’t the required skills to provide you with a species identification. Due to its size, we suspect this individual was searching for an appropriate place in which to pupate. Of one species, the Bug Lady on the University of Milwaukee website states: “When it’s time to pupate, they make a minimalist pupal case using silk and leaf litter.” We would release it on the ground in a protected area with leaf litter that will not be cleared in the near future. Many pupating caterpillars form a cocoon in leaf litter on the ground, and fastidious leaf raking in suburban yards likely produces numerous casualties. Underwing Moths are so named because their forewings are often camouflages to resemble bark, while the underwings are brightly colored. The moth attracts attention when flying and then disappears, thwarting a predator, when it lands on a tree trunk.