It isn't a small version of this guy, is it? This is a black swallowtail butterfly caterpillar. They don't normally eat mint but could be there for carrot family muchables. Don't squish these ones. Move them to some queen anne's lace/wild carrot and they'll be happy!

By the way, even new members can post pictures. There are size limits so most use one of the free image services like photobucket, picassa, and so on to post images. The pictures below are in my Picassa account and I just link to them here.

FataMorgana

{{gwi:62582}}

No, the stripes on this one run the length of the body.

Here is a link that might be useful: Worm

That's just one of the many army worm or beet worm caterpillars. Most gardens have zillions of them at this time of year. I'd keep plucking them and tossing them somewhere the birds can find them. He's a young one...they will get larger as they eat more of your mint.

Thank you so much!

Any problem caterpillars in my garden, and I just apply BT (Bacillus thuringiensis). It is completely non-toxic to anyone except caterpillars, for whom it crystalizes the insides when they eat it. Very satisfying for cabbage worms and tomato hornworms.