I found io moth eggs on a hackberry tree in my yard May 18, 2017, and brought them in to document behavior and appearance. I have read that io moth caterpillars typically have 5 instars, but while some of my caterpillars were making cocoons, a few were going for a 5th molt. Some of these caterpillars just looked like larger versions of the 5th instar, but two of them looked different. The orange ventral triangles are attached to the red/white lateral bands with a patch of black. These caterpillars grew to 3 inches long before spinning cocoons. One of the very early caterpillar photos of io moths on this site shows a similar coloration pattern, but I have never seen this pattern in my other searches. I had found a second clutch of eggs a week after this first one, and a few of those caterpillars are also 6th instar now, but none have this coloration.