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Tent caterpillars

This is the time of year to see caterpillars! As you wander around in the nature of your neighborhood, keeping a sharp eye open will reveal a lot. Most caterpillars taste good so they must hide well! (of course, we wouldn’t really want to eat them – although some are good if you cook them first – but birds will!)

If you want to see the caterpillars who live near you, rule 1 is to go slowly.

Usually, you don’t see the caterpillar first, you see the signs of the caterpillar. Here are some signs:

  • Chew marks on leaves
    • There are many ways leaves get damaged.
      • Sometimes they get torn by people going past quickly.
      • Sometimes a disease will weaken certain areas of a leaf and they will fall out.
      • Sometimes bugs with piercing sucking mouthparts will inject enzymes into the leaves and suck out the contents of cells, leaving brown areas.
    • But sometimes they get chewed by caterpillars.
      • Usually, this starts on the edges of the leaves and takes the form of little half circle shapes. (Think about a caterpillar standing on the edge of a leaf and eating as far as it can move its head... it makes a little arc.) There are some movies of caterpillar eating here.
  • Folded or rolled leaves
    • Many caterpillars hide inside leaves! They can roll them up and secure them with silk, or fold them over.
    • There are also beetle larvae and spiders who do this.

What YOU Can Do – about rolled or folded leaves

Rolled leaves are often very complex constructions made at great effort to the animal inside.

The utmost respect should always be used when deciding to unroll them!

The Ten Observation Rule:
Our general rule for deciding whether or not to unroll a leaf is to count the number of other rolled leaves in the area. If there are ten or more, we think it isn’t a bad choice. It is still disrespectful to the animal, but not so much to the population and habitat. If it will bother you to harm the caterpillar inside, don’t unroll it!

If you choose to unroll a leaf, go slowly and notice how well-constructed it is. Each circuit of the roll is stitched together carefully. In most cases, you will find a small larva inside. You also may find … poop!

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All animals poop – if you eat, and you don’t poop, you’ll explode!

The official word for bug poop is frass.

This can be a search clue for predators. Many animals try to conceal their droppings in some way.

In the case of the leaf-rollers above, they usually keep their frass inside the leaf roll. Others, such as many walking sticks, flick their abdomens and toss their poop far away from them.

You can often find the location of caterpillars by noticing accumulations of frass on leaves. Caterpillars usually hide under leaves so it can be very difficult to find them. But, if they drop their poop right down underneath themselves, you can look at the leaf above the pile! Even some predatory wasps and birds know this!

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Eastern Tent Caterpillars (Malacosoma americanum) tentA

Almost everyone has seen the tents made by these guys in the mid-late spring in the Northeastern United States. They find a corner of couple of branches and start making webbing. As the family of tentBcaterpillars grows, so does the web, until it looks like a tent in the tree. Very cool!

What YOU Can Do
You can learn some interesting things from these caterpillars.

For one thing, when you look at the tent, you will see a bunch of small, black round things inside. Many people assume these are eggs.

poopABut caterpillars don’t lay eggs. Moths do.

  • Actually, if you look closely around the tree, you will find a black, collar-like masswrapped around one of the branches. It will look sort of like Styrofoam with a bunch of little dots on it. These are the eggs! The mother moth laid them the previous Autumn and they survived in this mass throughout the cold Winter. All the caterpillars in the tent came from this egg mass. (You can see a picture of the egg mass here - then come right back!)

So what are the little, black balls? Frass!

  • But if you were an Eastern Tent Caterpillar, wouldn’t you stick your abdomen out of the side of the tent and not poop inside your home?! Think about what would happen if all the caterpillars thought like that. The tent never moves. There would be a huge pile of frass on the ground, pointing right up to the nest. Predators like raccoons and rats could just look up from the pile and locate the tent easily.
  • It’s better to strategically poop in the inner portions of the tent, and as it grows move outward. Then, if a bird or some other predator starts poking around in the nest for a nice lunch, it’ll get a mouthful of frass instead! Great defense!

Before you move on, there are two other things to notice.

trailALook carefully at the branches near the tent. You may notice small trails of silk all over leading around the tree. Eastern tent Caterpillars generally feed at night. They use the silk glands near their mouths to lay down a trail to follow back home and to help them hang on to the tree better. If you watch some of the caterpillars as they walk around, you’ll even notice their heads wagging back and forth laying down silk as they go.

Also, look at one caterpillar. Look at how beautiful it is! Notice the small, blue spots on each side of every segment. Look at the squiggly lines that run from head to the end of its abdomen. Look closely at the intricate designs on these guys.

caterpillarANow, many people consider Eastern Tent Caterpillars to be pests (one web site I found refers to them as ‘native pests’ – I am not sure that is possible if they were here first!). They do eat a lot of leaves and can do serious damage to smaller trees. But – there are still plenty of trees, so they obviously don’t cause major trouble to native habitats. That said, if you have some beautiful, expensive (perhaps non-native) trees in your landscaping, you may want to manually remove the nest. If you just pull it out, the caterpillars will not survive on their own – they’ll be eaten by birds or ants or raccoons or something. Respect is a tricky decision!

Oh yeah, and be careful when you are out in the field this time of year.... check out this little hitch-hiker I found before I headed back tickAfrom getting these photos! For what it's worth, this Dog Tick isn't likely to spread any diseases to you (DeerTicks might), and they cannot bite you on the plams of your hands! Your palms and the bottom of your feet have an extra layer of skin (and so they don't have hair) that the tick cannot penetrate.

And have fun looking at the BUGS!

(see our Programs pages about how you can have us come and take you out to show you the BUGS! with BUGMANIA!, our outdoor walks!)

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