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Caterpillar Hunting at Night

Updated: Apr 26

Many Caterpillars Glow Under UV Light

Fall Webworm Moth Caterpillar GLowing under UV Light
Fall Webworm Moth Caterpillar
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"The caterpillar does all the work, but the butterfly gets all the credit." ~ George Carlin

Many Caterpillars Glow Under UV Light

Did you know that a lot of Ohio caterpillars are nocturnal? They are active at night and sleep most of the day. When they are resting, they often hide at the base of plants, in crevices, or wrap themselves in leaves. Therefore, we see few varieties of caterpillars during the day.

If you are looking for a fun activity to do outdoors with your children, or want to go by yourself, you can go caterpillar hunting at night. And the best part is, you can do it in your own yard.

Definite Tussock Moth Caterpillar Glowing Under UV Light
Definite Tussock Moth Caterpillar

What Caterpillars Glow Under UV Light?

Many types of caterpillars glow at night. From slug moth caterpillars, Luna moth caterpillars, Polyphemus moth caterpillars to Sphinx moth caterpillars, among others. So, if it is a striking caterpillar, you can almost bet it is hiding during the day.

We have found Ohio caterpillars such as the Woolly Bear (aka Pyrrharctia Isabella Tiger Moth) Giant Leopard Moth caterpillar (big black fuzzy caterpillar), and the Milkweed Tussock Moth caterpillar cease to glow. Since there are many caterpillars and insects active at night that do not glow, be careful where you are walking. You would not want to accidentally step on one or get bit/stung.

Banded Tussock Moth Caterpillar Glowing Under UV Light Ohio Caterpillar
Banded Tussock Moth Caterpillar

What is a UV Light?

A UV light (ultraviolet) is also known as a blacklight. It is a special type of light that emits ultraviolet rays. These rays are often used to make posters glow, detect counterfeit cash, find evidence at crime scenes, look for unsanitary conditions, and search for coolant and oil leaks. But that is not all they can be used for. They are also a great tool for hunting bugs and scorpions at night.

UV flashlights are fun and functional tools. Not only are they used in forensics, but you can find them in nightclubs too. UV lights can make an object glow if it contains the chemical phosphor. Phosphors react to the UV light and, in turn, emit light.

We were using a small UV flashlight that we purchased at Harbor Freight. It was a nice little flashlight, however, you need to get extremely close to the foliage to spot a caterpillar. We replaced it with a Vansky 51 Ultraviolet LED Flashlight. If you are looking for a powerful little UV flashlight for caterpillar hunting, check out the Vansky flashlight by clicking HERE.

Hunting for Caterpillars at Night

You only need 2 things: a regular flashlight and an ultraviolet flashlight. We would also recommend that you wear a pair of UV blocking glasses to protect your eyes.

Use your regular flashlight to light your path, so you avoid tripping or running into anything. Once you get to the area you want to scan for caterpillars, turn off the regular flashlight and turn on the blacklight flashlight. Shine the UV flashlight over the foliage and stems. Make sure to look at both the tops and the bottoms of the leaves.

A caterpillar will glow a bright white or green under a UV flashlight. Leaves often glow purple. However, you may notice other things that glow under the UV light such as spiders, moths and trash. When we first started searching for caterpillars at night with a UV flashlight, we were amazed at how many tiny pieces of trash were lying around. So, it might be a good idea to take a small trash bag and clean up as you go.

That is all there is to it.

Arrow Shaped Micrathena Spider Glowing Under UV Light
Arrow-shaped Micrathena Spider

How to Look for Certain Types of Caterpillars

Do you have a caterpillar on your bucket list you cannot find no matter how hard you try? The best way to find that caterpillar is to do a little research. Find out what host plants they like to eat and search out those plants.

When looking for caterpillars, remember, they like to hide under leaves. This helps keep them safe from predators. Also, keep an eye out for frass. Frass is a fancy name for poop. These little nuggets can easily give away the position of a caterpillar. Especially when there are large amounts in one area.

Here are a few resources from the Ohio Division of Wildlife that can help you learn more about Ohio caterpillars, Ohio moths, Ohio butterflies, and their host plants. These field guides have a lot of helpful information. However, not all Ohio caterpillars are listed.

Early Instar Sphinx Moth Caterpillar Glowing Under UV Light
Early Instar Sphinx Moth Caterpillar

Do Not Touch the Caterpillars

Please abstain from touching or harming the caterpillars. Let them live their lives and become the beautiful butterflies and moths that help pollinate our trees and flowers. There is no reason you need to touch or pick up a caterpillar unless you are experienced in raising them. If you handle them improperly, you can kill them or hurt yourself.

Be Safe When Looking for Caterpillars at Night

There are a few things to consider when caterpillar hunting at night:

  • Know the Terrain

Before you search an area for caterpillars at night. Take a good look at the terrain. You want to avoid falling or spraining an ankle. You should also make sure that there are no active nests or poison ivy.

  • Take a Regular Flashlight

The UV Blacklight Flashlight will help you navigate to a point. But it will not provide you with the light needed to move around safely.

  • Don’t Look at the Light

Strong UV lights can be dangerous and damage your eyes. Never look directly at the light. Instead, it is a good idea to wear a pair of UV blocking glasses.

  • You Are Never Alone

No matter where you live or where you are caterpillar hunting, you are not alone. If you live in town, you know your neighbors are around. And if they see you outside with a UV flashlight, they might think you have lost your mind. There are also insects and wild animals everywhere. And they are often active at night. Always be aware of your surroundings and stay safe.

  • Don’t Touch the Caterpillars

Handling the caterpillars can kill them. Even though this is a great reason not to handle them, it is not the only reason. There are quite a few venomous caterpillars in Ohio. Their hairs and spines can harm you.

Below are some stinging caterpillars and poisonous Ohio caterpillars:

Definite Tussock Moth

Definite Tussock Moth Caterpillar Ohio

Hag Moth Caterpillar (Monkey Slug)

Hag Moth Caterpillar Ohio

Hickory Tussock Moth

Hickory Tussock Moth Caterpillar Ohio

IO Moth Caterpillar

IO Moth Caterpillar Ohio

Milkweed Tussock Moth

Milkweed Tussock Moth Caterpillar Ohio

Nason’s Slug Caterpillar

Nasons Slug Caterpillar Ohio

Saddleback Moth Caterpillar

Saddleback Moth Caterpillar Ohio

Skiff Moth Slug Caterpillar

Skiff Moth Slug Caterpillar Ohio

Smaller Parasa Caterpillar

Smaller Parasa Caterpillar Ohio

Spiny Oak Slug Caterpillar

Spiny Oak Slug Caterpillar Ohio

Stinging Rose Caterpillar

Stinging Rose Caterpillar Ohio

Sycamore Tussock Moth

Sycamore Tussock Moth Caterpillar

White-Marked Tussock Moth

White Marked Tussock Moth Caterpillar Ohio

Yellow-shouldered Slug Caterpillar

Yellow Shouldered Slug Moth Caterpillar

Each person will have their own reaction to poisonous caterpillars. Some people may not experience any symptoms, while others may have a slight rash. Then there are those that may have a bad allergic reaction and need to seek medical attention. While not all Ohio caterpillars are harmful, the best advice we can give you is DO NOT TOUCH ANY CATERPILLARS.


Glass caterpillar figurine, hand blown glass caterpillar,
miniature caterpillar, murano caterpillar, caterpillar ornament, glass figurine
Hand blown Glass Caterpillar Figurine Found on Etsy

Find Caterpillar merchandise in our Zazzle Store HERE

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