I found this big moth sleeping on a wall, and happened to have my camera in my pocket, so I took some pictures. That's probably how my butterfly site expanded into moths. Wendy identified it as an IO Moth.

Later I found IO Moth caterpillars too, but I did not bring them home to raise because they sting.

This is the IO Moth caterpillar. IT STINGS!

Butterfly caterpillars, as far as I know, are fine to handle; mine have never bothered me (get your own safety advice, don't count on mine!), but some moth caterpillars, like this one, are supposed to be very uncomfortable to handle; I didn't pick it up to check.

Close-up, the IO Moth caterpillar looks like it has a bunch of tiny sea urchins stuck to its back, and the spines look dark at the tips. This is definitely a hands-off bug!

If I'd known it was an IO Moth when I found it, I'd have nudged its wings open to get a picture of the eye spots.