Caterpillar colonies

[LadyShea]

There are two of these on one tree. We took this photo yesterday. They are called Walnut Caterpillars, but I thought that was an oak tree.

[The Lone Ranger]

The true "Walnut Caterpillar" is the species Datana integerrima. They do indeed feed on plants in the Walnut family, and are not known to feed on oaks. (And from I can see of the leaves, that is indeed an oak tree.)


What you have there is actually the closely-related species Datana ministra, commonly called the "Yellow-Necked Caterpillar." This species does indeed feed on oaks.

Cheers,

Michael

[LadyShea]

Thanks for the proper name, I was doing my best to ID it from online descriptions...which is not very efficient. They have stripped a few branches, but not nearly enough to damage the tree or for me to want to take control measures. Interesting backyard viewing, that's for sure!

[The Lone Ranger]

Yes indeed!

This species can become a pest and enough colonies can seriously damage a tree. But if you have only the two colonies in a mature tree, they shouldn't cause any real damage, I should think.

The adult form is sometimes called the "Handmaiden Moth" (I have no idea how they got that name, alas, but I don't doubt it's an interesting story). They're superbly well-camouflaged against tree trunks or dead leaves, but you may be able to find them about, especially around August and September.

Cheers,

Michael

[Ensign Steve]

How amazing! You get the coolest critters in your yard.

[LadyShea]

I do have cool critters. Another exciting sighting was of an Eastern Eyed Click Beetle

Our yard was also host to a banana spider "nursery" this year, and we got to watch a dozen or so grow from little bitty things to large adults, at which point they leave the area.

Previously we never saw them until they were enormous adults and then they are very solitary.

[JoeP]

"Caterpillar Cluster" (as you named the gallery image) sounds like one of those delicious choccies from the Monty Python sketch.

[JoeP]

Also,

[LadyShea]

Also, when you disturb them, they kind of rear up their head and tail in a defensive posture...and it's effective as they all do it at the same time so it looks kinda like one big organism.

[JoeP]

Originally Posted by LadyShea

they kind of rear up their head and tail in a defensive posture

Can you post a piccie of this?

[LadyShea]

It's very quick and I haven't been able to get a picture of them all in this position. I found this online though of one

[The Lone Ranger]

This species is parasitized by a number of wasp and fly species, and this distinctive defensive posture is thought to have evolved to make it harder for a parasitic wasp to sting the caterpillar in a sensitive place.

It's pretty nasty. Some wasp species specialize in parasitizing caterpillars. They'll sting the caterpillar in a nerve cluster, paralyzing it but not killing it. The wasp then hauls the helpless caterpillar to a prepared burrow, lays an egg on it, then seals the burrow. When the wasp larva hatches, it burrows into the poor paralyzed caterpillar and eats it alive, saving the vital organs until last, so that it stays alive until the end.

Darwin once said that this was the sort of thing that convinced him there was no benevolent God watching over Creation.

Cheers,

Michael

[Ensign Steve]

Maybe the caterpillars have free will.