io moth caterpillar showing anal and abdominal prolegs


animal, vo•cab•u•lar•y

(adj.) conspicuous and serving to warn

It never fails – find a hairy caterpillar with kids and they always claim that it’s “the one that stings!” To be fair, this one was virulently green with black-tipped spines and a bold red stripe- it certainly looked a bit dangerous. Never having met this beauty before, however, I decided to test the theory.

First, a light stroke to the hard little head.

No bite.

Then, a gentle pat to the black-tipped hairy green back.

No sting.

Finally, a gentle nudge to lead it onto my fingertip.

No blood. Slowly, the kids became convinced that although it could be dangerous, it didn’t seem aggressive… so they edged in for closer looks and brave glancing touches. We named it George. After we admired it thoroughly, we put it back on the fence post where we had originally discovered it and said our goodbyes. As we walked away, I looked it up and discovered that the kids were right! 

io faceThose black tips?

They are designed to embed in the skin of a potential predator and then snap free from the caterpillar. Apparently, less gentle contact or perhaps contact with thinner skin than mine, can result in days of unpleasant itching. Plus, the denser the hairs on a caterpillar, the more difficult for wasps to lay their eggs in the moist and protein-laden body… which would turn the caterpillar into a living larder for the wasp larvae. George seemed to have a very nice caterpillar coat of armor.

That red stripe?

On this species, it’s a sign that the soft and squishy larva is in its fifth and final instar stage – one precious step before the protection of a cocoon. This caterpillar spent significant time and energy to survive this long and its very last larval layer blatantly advertises, “Don’t mess with me.”

And, by the way, those bright red legs?

Not legs at all! Caterpillars can have up to 5 pairs of prolegs, which unlike their true legs, are their primary means of transportation. Each proleg consists of a planta (like a suction cup) ringed at the bottom with a crochet (made of hairs called setae).  As is often the case in nature, important body structures evolve with speciation – so the number of prolegs and the design of the crochet can help nerdy nature lovers identify caterpillars down to the family level… and with the help of the internet, we learned that George is an io moth caterpillar, formally known as Automeris io. Side note: No humans or caterpillars were harmed in this adventure. And we found 3 more!

Want to see some amazing macrophotography videos about other caterpillars?

Watch Caterpillar Cameos from Biographic.

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