Tag Archives: automeris io

Io Moth Caterpillar – ouch

I walked and drove past this Mulberry tree for a week or so, while going up and down my driveway, and noticed massive leaf loss.  I didn’t immediately do anything about it because I figured that it was the usual fall grasshopper destruction.  On my way down to the mailbox by the road, I decided to walk over to the 7 foot, second year Mulberry tree and check it out.  I was very surprised to see about 14 giant, green, prickly caterpillars. These things were about 4″ long. They were covered with rows of bur looking things that turned out to be toxic stingers.

Mulberry tree eaten by io moth caterpillars

The main branch has been stripped of leaves by these moths.

Mulberry main branch stripped by io moths

io moth caterpillars eat leaves to stems

I was not prepared to remove these pests – I did not have my leather gloves my pocket so I tried to flick one off with my finger. Ouch. I only knocked the critter half way off but received a very severe sting. I had to find a stick to finish knocking off the other caterpillars.

This is an io moth caterpillar:
io moth caterpillar
This is an io moth:
io moth

I had expected fire ants to be the first predators to arrive on these dead caterpillars, but it yellow jackets were there first.

yellow jacket on dead io moth caterpillar

Three yellow jackets on green bug juice from the caterpillar.

yellow jackets on dead io moth caterpillars

Doing some research to find out what these giant stinging caterpillars are, I found that there are public health warnings out about them. My sting could have resulted in a serious allergic reaction. The burs are hollow, poisonous hairs that are connected to underlying poison glands. The resulting allergic reaction could last a day or 2, with possible nausea for the first few hours.

The “Automeris io” moth caterpillar has long rows of tubercles armed with green and black spines. This thing is classified as a “Urticating” caterpillar. They have urticating hairs or bristles, meaning ‘irritating hair’. They are a defense mechanism, like a nettle plant’s hairs. The immature stages of several species of moths in states east of the Rocky Mountains are venomous to humans because of their external poisonous spines and hairs.

While looking at the tree to find all of the caterpillars, I found a round, clay, vase like structure with a hole in it. I have seen these on other plants around the yard. They are obviously some sort of bug home.

round clay like structure made by bugs

Webbing with caterpillar poop.

closeup of clay like structure in tree made by bugs

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