Wednesday, August 17, 2011

Monkey Slug and Robber Flies

This has definitely been a good year for finding interesting creatures. Sometimes it’s hard to tell what you’ve actually found. This looks like a character from the movie Gremlins.

From another angle it looks like the head of a Leaf-nosed Bat. The ears may be a little large, but it certainly has a bat-like appearance.

Actually, it’s a moth larva known as a Monkey Slug, the immature form of a Hag Moth. The shape supposedly resembles the shed skin of a Tarantula. I’ve not seen such a skin, but the shape of the caterpillar is distinctly spider-like.

Like other slug caterpillars, the head is concealed beneath the body. If you think of this shot as a puppy face, the caterpillar head is below the chin where it touches the leaf.

This species is not supposed to sting, so I used my finger to roll it onto its back. My finger remained undamaged throughout the operation. From this angle the caterpillar appears to be a living creature instead of patch of fungus or bit of debris.

While photographing the Monkey Slug, a swarm of small Robber Flies began using my hand as a hunting and feeding platform. They would dart out, grab a tiny fly and return to my hand to consume their meal. Fortunately I carry a back-up camera, so I was able to get some shots of the Robber Flies sitting on my regular camera hand.

It didn’t take the Robber Flies long to eat a tiny fly and rush out to grab another. I’m glad I was able to assist with the capture of their evening meal.


  1. HI Steve..I was ready to tone you out when I saw this creature , because I thought for sure it was a spider : (OOOOO)
    We I am pleased to find out that it wasn't ,but some funky looking slug that doesn't bite!
    Happy mid week to ya!!

  2. Yes, you certainly do find some interesting critters!

  3. Love the slug caterpillar! You're right to be cautious about the sting though: I found a saddleback caterpillar once and got stung really badly. Ow! My skin was burning for about four hours. Neat looking critter though.

  4. It doesn't sting? Every site I have seen says it can sting with its urticating hairs.

  5. You do have the most amazing creatures, I've walked the woods for years and never saw a monkey slug or did but didn't know it. great shots.

  6. Hi, grammie g. You know I wouldn’t spring a spider on you without any warning.

    Hi, Lois. I hope my luck continues.

    Hi, Jodi. I bump into a few saddleback caterpillars each year. I can say with certainty that I’m not immune to their sting.

    Hi, Janet. Wagner says in his Caterpillars of Eastern North America that based on his personal experience, the Monkey Slug doesn’t sting. It seems to make sense that a creature that avoids predation through mimicry probably wouldn’t also develop a stinging defense. It’s also possible that the caterpillar can only sting at a certain stage of development that he and I were lucky enough to avoid. Since most believe the Monkey Slug can sting, I doubt that there are many people actually testing this ability.

    Thanks, Michael. I probably blindly walk past amazing things every day. I don’t think our eyes were made to easily see much of this stuff.