We have seen this black worm around our yard- under rocks, and crawling on our back porch and driveway. In general, I'm a critter-lover and just enjoy watching unique creepy crawlies in nature. BUT these guys look ominous. Can you help identify this worm so we can find out if it's harmful? We've seen information on the Land Planarian (flatworm) on the internet...but we really don't think it's a match. If you know what this worm is, please share!!

hope others join in, but it looks like a leech.

We are wondering if it might be some type of land leech. We also contacted an entomologist from TAMU, but he's also uncertain what this is.

That is indeed a land planarian, of the Platydemus Manokwari variety it looks like. I'm from Hawaii and these were introduced here to control the Giant African snail population.
They spend their time eating snails, slugs, worms, and eachother, and don't pose a threat to humans.

The problem with identification on this is that the head shape isn't distinct in this shot. Planaria have a triangular head, typically. The rest of it looks like one, though.

This is the kind of mystery critter that you don't want to leave out there, and you don't want to smash it and walk away (all of the bits become new ones). This, if it is a land planarian, needs to be wrapped up in something it can't get out of and thrown in the trash.