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How to Find Caterpillars


What's the Best Way to Find Caterpillars?

This guide will help you find the caterpillars that are living all around you. Caterpillars are the immature stage of butterflies and moths. They do the eating and growing for the adult stage, because butterflies and moths don't grow or get bigger once they hatch out, and many of them don't even eat at all. So the caterpillar is, in a very real sense, an eating tube. It has a mouth at one end and a butt on the other, and all it really lives to do is eat, poop, and get bigger. Everything else about a caterpillar is basically some kind of strategy for avoiding predators and surviving to become a butterfly or moth. All of the fur, horns, bumps, spines, and camouflage are just developments that might help keep it from being noticed by a hungry moth or lizard, or surviving the encounter in case they do get noticed.

Speaking of being noticed, this article is intended to help you find caterpillars. They can be devilishly hard to spot when they're hanging out among the leaves and branches of their food plant, so if you don't find any most of the time, don't feel bad! Scientists and professional entomologists often have just as much trouble as you do. They sometimes spend hours and even days just to find a few caterpillars.

So have fun and good luck with your caterpillar hunting! And if you do find one, please leave a comment at the end of this article. Thanks!


The Best Way to Find Caterpillars -- Look for poops on the ground

Who flung poo? Probably a caterpillar did

Caterpillars eat a lot, and so it follows that they also poop a lot. It follows that one way to find caterpillars is to look not in the leaves but on the ground, where the poops fall and give the caterpillar away. There's nothing like a bunch of caterpillar poops on the sidewalk to tell you that there's a busy caterpillar living somewhere up above. Caterpillar poops look like little brown barrels or hand-grenades, and the bigger the caterpillar the bigger the poop. It's interesting that some caterpillars have evolved a “pooping behavior” in which they flick their poops away with their butt muscles instead of letting them drop (who flung poo? A caterpillar, ha ha). It follows that this means some predators have learned that poops on the ground mean a caterpillar is munching away above. It's a constant battle! Nature is truly amazing.


The Best Way to Find Caterpillars -- Look for leaf damage

Since caterpillars eat leaves, one way to find them is by finding half-eaten leaves on trees. This is a very good sign that there's a caterpillar on the plant. Experienced caterpillar hunters know that the kind of leaf damage can tell much about what kind of caterpillar it is, and where it might be: damage that has brown edges is older, and the caterpillar has probably moved on. Fresh edges mean the eating is more recent, and the caterpillar might be just a few inches away.

Then again, some caterpillars have evolved behavior that covers their tracks; they'll completely cut through the petiole of leaves they have chewed, causing them to fall to the ground. Good luck with these guys!

Watch as this big tomato hornworm chows down!

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The Best Way to Find Caterpillars -- Look from top to bottom

Many caterpillars eat during the night and then hide at during the day. If you suspect a caterpillar is on a plant, don't just look around the leaves. Take a moment to investigate the base of the plant. That's where caterpillars like to hide when they're not eating. It can be very hard to see them, hunkered down in their little hide-out. Be patient and keep your eyes wide open.


The Best Way to Find Caterpillars -- See Through the Camouflage

It's hard to believe how good at hiding in plain sight caterpillars can be. For example, tomato hornworm caterpillars eat the leaves of tomato plants in your garden. They grow to be huge -- up to four inches long, fat and so full of food that they're actually heavy in your hand. You can be sure they're eating your tomatoes because they leave piles of huge poops everywhere, and the leaves on your plants will show evidence of severe munching, if there are any left at all. And yet actually finding them can be nearly impossible. I've searched one little tomato plant forever before suddenly realizing that a gigantic hornworm has been sitting a foot away from my face the whole time. This is because tomato hornworms are the exact same green as tomato leaves, and have subtle white diagonal lines all down the body, which precisely mimic the veins in tomato leaves. They rest in such a way as to maximize the resemblance. So these giant caterpillars just melt into the tangle of leaves of the plant, and you and I can have a very hard time finding them.

There isn't enough space here to talk about all of the ways that caterpillars hide in plain sight. Just keep your eyes wide open and don't believe everything you see. That twig or dried leaf or shadow may very well be a sneaky caterpillar hiding from you.

What the caterpillar calls the end of the world the master calls a butterfly.

— Richard Bach


The Best Way to Find Caterpillars -- Look on the Ground

One good place to find caterpillars is crawling on the ground. That's because when it's time to turn into a moth or butterfly, caterpillars often leave the food plant and go looking for a place to rest while the Big Change takes place. It's while they're cruising along, looking for the right place, that you will often spot them. The good news: since the caterpillar is already looking for a place to pupate (change into an adult), you can keep it safe and sound in tupperware with a folded papertowel in the bottom, and chances are it will pupate in a day or two. They're done eating, so you don't have to worry about leaves or food of any kind. It's probably the easiest way to raise a perfect adult specimen from a caterpillar.


Hope You Found Some Caterpillars!

You never know if you're going to find a caterpillar or not, but the tips I offered here will give you your best chance. In my experience, you often find caterpillars when you're not even looking for them. Be patient and keep your eyes open, and you never know what will turn up.

A Great Caterpillar Guide Book

I use this book all the time -- it's perfect for young scientists and the people helping them learn.

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