Caterpillars

A few weeks ago as I ambled down the path of the Dinosaur Trail I noticed a black-bodied caterpillar coming up the path directly at me. The caterpillar was about an inch and three quarters in length and had long, white, silky hairs (setae) sparsely spaced along its length. I hadn’t seen one of these caterpillars before so I took a photo for later indentification.

The black caterpillar with long white hairs.

As I continued down the path I saw another black caterpillar with long silky hair walking in pretty much the same direction as the last. I then saw another. And finally, I saw a few more at the base of a walnut tree directly opposite the Alamosaurus, the big long-necked dinosaur on the trail. The caterpillars were headed away from the tree, a clue to their identity.

The caterpillar at the base of the tree.
The Black Walnut Tree.

Caterpillars come in a variety of shapes and sizes. Some are hairy while others are smooth-skinned. Some caterpillars have long spikes on their heads or other parts of their bodies, others don’t have spikes or spines. And some are gregarious while others solitary. This caterpillar was obviously gregarious, there were a bunch of them, and they had probably just finished munching on the leaves of the Black Walnut that I was now standing under and marching off to find a safe place to pupate.

It didn’t take very long to figure out that my caterpillar was, of all things, a Walnut Caterpillar (Datana integerrima). It’s a plain looking caterpillar, but interesting. There can be hundreds of them on any particular nut tree; hickories, pecans, butternuts, or walnuts. One curious fact is that when they molt, the whole congregation (or nearly so) molts at the same time on the trunk of the tree. That means that when they are ready to molt into another instar (another stage of their larval life) they stop eating, crawl over to the trunk to form a cluster (they may be stacked 2 or 3 deep), molt and then head back to the leaves to start munching again. Hmmm.

Three or four days after my encounter with the Walnut Caterpillars I was staring over the railing of the boardwalk in Explore the Wild. I was looking for tree frogs clinging to the smartweed below me. I did see a few tree frogs, both gray and green, but I also saw a tiny red and yellow object next to a piece of missing smartweed leaf. Must be a caterpillar.

That must be a caterpillar in the smartweed.

I only know of two caterpillars that eat this stuff, the smartweed that is, Tobacco Budworms and Smartweed Caterpillars. Judging by the bright colors that I could see it had to be a Smartweed Caterpillar. Besides, if I remember correctly, the budworm tends to eat the flowers, not the leaves of the plant. The caterpillar that I was looking at was going to town on the leaves.

Chowing down on the leaves of the smartweed in the Wetlands.

Smartweed Caterpillars, or Smeared Dagger Moth Caterpillars (Acronicta oblinita) are variable in color. They can be mostly black, mostly orange, or a combination of the two, but they always have the yellow stripe and spines.

Here’s a Smartweed Caterpillar on another plant taken a few years earlier. Notice it’s slightly different in color but still has the yellow stripe and spines.

Now to the third caterpillar. This past week, I was strolling along in Catch the Wind, minding everyone’s business (I’m supposed to do that), when I noticed a large number of branches on a nearby Willow Oak were missing their leaves. This same tree has been the object of caterpillar infestations in the past. In fact, I expect to see Orange-striped Caterpillars (Anisota senatoria) on this tree every year, sometime in July or August (it’s August 1 as I write this).

A closer look at the tree and there they were, not one, two, or three caterpillars, but several dozen. Curiously, if you go in to have a really close look at these caterpillars, grab a branch and bring it in close, the caterpillars will drop off to the ground. This behavior must be some kind of defense against bird predation, although if I were a bird and saw one of these caterpillars drop to the ground, I’d go down to the ground too, pick that caterpillar up in my bill and gulp it down.

Over the next few days I saw several of these caterpillar squished on the pavement. They, like the Walnut Caterpillars above, crawl down out of the tree when it’s time to pupate. They travel to a safe place to pupate which may be some distance from the tree. Unfortunately for them, some don’t make it. They get stepped on.

But what’s unfortunate for the caterpillar may be beneficial to others. I saw one caterpillar being chewed upon by Yellow Jackets, one at each end. The Yellow jackets will chew off a big chunk of the caterpillar and bring it back to the hive to be fed to the colony’s larvae.

These two wasps work feverishly at removing chunks of meat from this caterpillar that was apparently making an attempt to crawl off and pupate.

And that, is the tale of the three caterpillars.

2 responses to Caterpillars

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    Georgia says:

    Greg, Will you show us the butterflies/moths that these caterpillars become?

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