Monday, March 26, 2012

Polyphemus moth caterpillar (September)

(Note: while the next several posts may not be exactly timely, I try to always post things in the order I found them.)

So we were hiking around during the 2011 summer/fall drought (meaning, bad for mushrooms), and my hiking pal came upon this bright bright BRIGHT green fat fat FAT caterpillar.
bright green caterpillar on the ground

It was the caterpillar of a Polyphemus moth (Antheraea polyphemus)—a big elegant silkworm moth, many shades of brown with nice eyespots on the wings. The males have enormous feathery antennae (a pic of one I found, here), for detecting pheromones from the females.

It was really hard to get a good photo of this caterpillar, because it wouldn’t stop walking. Apparently, at this time of year, they won’t stop walking. If you pick them up, they just keep walking. You try putting it on your friend’s arm to get a better shot, and they just keep walking. You try blocking it with a leaf, and it won’t stop walking.

I read that when these silkworm moth caterpillars are getting ready to make their cocoon, they stop eating, and start walking—they’re called “wanderers.” I’m guessing they’re looking for the right place to park for the winter?

If it tries to get around you and your leaf, and falls approximately 1” off a little rock, it might stop walking and curl up defensively.

green caterpillar back

This particular brand of (fat!) caterpillar has a tendency to withdraw their heads into their fat, translucent, luminous bodies when they’re not marching ever forward. Seems to be a characteristic pose they strike. I would probably do that too, if I had folds of beautiful, neon-green, floppy soft skin.

fat green caterpillar head withdrawn
Polyphemus caterpillar head  fat green caterpillar head

When he fell approximately 1”, thanks to my pestering him with a leaf, he grabbed onto a little clump of loose moss and leaf, and didn’t let go.

Polyphemus caterpillar underside prolegs

This gave me a chance to get a passable shot of his prolegs—something I never took any notice of, until a Flickr contact posted this exquisite macro shot of them. Since I saw that image, caterpillar prolegs have become one of my most favorite things in the world. The prolegs are the dark grey and brown crazy-shaped things (note the fifth pair at the very end). Of course you can see why I’m nuts about them. Ask my friends--they'll tell you! "Oh, don't get her started about prolegs..."

The prolegs are tipped with “crochets,” little hooklets all around the edge. (In my image you can’t actually see them--they're way too tiny--they’re on the very end of the brown bits.) The number, size, and arrangement of the crochets are used in identification. Who knew! Not me!

The six pairs of legs near his head are true legs—with joints and everything, and little claws at the end. Prolegs aren’t jointed, and have limited musculature. One source said they operate via hydraulics.

*Warning: if your supposed caterpillar has more than five pairs of prolegs (counting the ones at the very end), it is not a moth or butterfly! Run!

Anyway, rather than going on about caterpillar proleg crochets that you can’t actually see in these images, I’ll wander back to an overview of the super-cool prolegs. Of all the caterpillars I’ve seen in all my years of seeing caterpillars, I never really noticed their prolegs, which are bizarre, stumpy and wonderful. I never tire of caterpillar prolegs.

There’s also the issue of this caterpillar’s gorgeous translucence.  He really did look like a bioluminescent water balloon creature. If you click on the images to see full-sized, you can see how the light is passing through it, making him glow.

I’ve found more than one of their cocoons. I’m pretty sure whose cocoon it is, since I found one right before it hatched, and saw who was inside. Here’s one with a portion of the pupa’s exuvia still inside.

silkworm cocoon showing pupa exuvia

Well, that’s about it, really.


  1. Awesome! The color is fantastic! Thanks, I enjoyed it.
    I had never thought about prolegs before a couple of years ago when a friend had about 75-100 black swallowtail butterfly caterpillars on her dill. Cool critters.

  2. wow Lisa, this is the most amazingly coloured caterpillar ever seen I'm sure. The translucent green is mind boggling... how does mother nature DO THAT? Please please post these images to Flickr, I'd love to fav them... especially the shot of the underside. I too love prolegs, and have often wondered about them. To me they look like little elephant feet, but now I will be looking for much more detail. The link to that excellent proleg image - I followed it and was gobsmacked all over again!

    1. Elephant feet! Yes!
      I know, that guy takes unbelievable photos, I'm so glad he okay'd the link, so more people could see it.
      "I too love prolegs" is not something you hear every day...

  3. These are spectacular images. wow. Awesome.

  4. Coming from you, I am very flattered. Thank you.

  5. What does it eat? We found one today. ..

    1. I did not know before a quick internet search of "polyphemous moth caterpillar food" brought up this page:
      Looks like everything you'd need to know is there!

  6. Awesome pictures! I just seen one today and I took some pretty decent pictures of it

  7. I found one right now in my front yard a squirrel was gonna dine on him so I took him outta danger and I'm gonna set a den for him to get set up

  8. We could one yesterday walking across the road here in Ohio

  9. Sorry we found one walking across the street yesterday in Ohio