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.

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:


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.


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 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!


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. 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.

  • 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.

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