It could be birds damage, reminds me of my kale (some birds just loved it :) or some other critter besides birds, somebody defiantly nibbled on the mint. Don't worry about the mint, it is very tough and will recuperate.

Slugs work at nights till morning and then go to their hiding place( underneath the pots, rocks, cracks ... somewhere that they can stay cool during the day. NOT ALL slugs/snails leave a track all the time. They have many favorites but when hungry will eat mints too.

Go out wit a flashlight shortly after dark and check.

There are other insects , like Earwigs, that also do similar damage. They also come out at night and hide in damp places just like slugs/snails.

Could be a fat, happy, bright green little worm that hides under the leaves and on the stem, the same color as the mint. They can strip a plant very quickly. The only way to control them is to carefully search every day (sometimes I do it twice a day) and pull them off and kill them by hand. They will multiply fast, but after you kill a bunch of them for say, a week, they don't come back. For a while. But you pic does look like slugs/snails. Put some old beer in a shallow plate, and dig out a little hollow in the dirt so the lip of the plate is level with the dirt. Leave it out over night and see dead slugs in the morning. If so, there's your culprit.

Thanks for the replies - I inspected & dug, I went out at night (a couple of times) to inspect - not a thing. I even got out a magnification glass to see if I could spot some tiny insects... to no avail. - Update is is, the mint stopped being eaten on night two and is now bouncing back and producing new leaves for my sweet tea (-: YAY, not bad considering the 100 to 112 degree days we've had here, yall were right - hearty little plant! (-: Susie

oh my goodness this has happened to both my mint plants in the last few days and this morning i found a green worm type thingy does anyone know how to get rid of these worm thingys?

oh my goodness this has happened to both my mint plants in the last few days and this morning i found a green worm type thingy does anyone know how to get rid of these worm thingys?

GREEN WORM ? just squish them. There should not be that many of them around.

Not to worry. Just water your mints. They will come back even stronger.

txsusie, seems like if you had snails or slugs, they would have done equal damage to the lower leaves. I have never had problems with critters eating my peppermint that is planted in the ground outside. I wonder if a cat or dog might do that if it had a diet defficiency or an upset stomach? Regarding the night inspections, I had lots of damage to some teacup roses one year. Something was eating the tops off of the buds but I couldn't find grasshoppers or anything. I went out one night with a light and found bookoos of june bugs feasting away.

I’ve had the same thing for years, my mint striped overnight by bright green fat caterpillar grub thingy‘s, I’ve put the mint into a terracotta pot up on top of my terracotta outdoor table, and GREAT they can’t be got at now, and is growing lovely.

Just walked out my door because I heard a bird on my balcony (third floor). She (starling) was pulling the leaves off my spearmint plant and flew away with them! It's spring. Maybe she wants the nest to smell good! LOL

Maybe that fat green worm would work well with tequila, lime juice, sugar and ice.