Jmcat - the picture is of a rove beetle, family Staphylinidae. There are probably thousands of species, and most, if not all, of them feed on other insects. You can always identify them by the fact that the hard wing covers of the typical beetle are very short, leaving most of the soft abdomen exposed, but they do fold up a fully functional set of wings into that small space. Hope this helps - Tucker

Thanks for the response! I never would have guessed that this was a beetle. Do you think they would eat springtails?
-Jmcat

I think it very likely that they'll eat springtails!

Well, I have plenty of springtails in my waterfall, so maybe that's what they're eating. Speaking of springtails, they don't hurt plants, do they?
-Jmcat

I think of springtails as scavengers, but I guess they might nibble on tender roots, etc. They're in your terrarium because of the moisture.

You could probably cut back on the population by using some horticultural grade diatomaceous earth.

What would they be scavenging?

Organic matter....potting medium, plant stuff, etc.

Thanks for all the help! I had been throwing them outside when I saw them, but I won't now that I know they won't harm the plants.
-Jmcat