Past few days black caterpillars on plants, crawling up the side of house, mating?,

Bad cat? Which is it?
What do I use to eradicate them?

Are they bad? What do they grow up to be?

It kinda looks like the Giant Leopard Moth caterpillar. http://www.squidoo.com/black-f...
--but not really because your caterpillar has thorny/barbed looking spikes.

Maybe @JRsbugs will know?

Thanks for the buzz Christine! I have come across something similar but what that was I don't recall, I think it's a butterfly and not a moth caterpillar.

It's only the adult butterflies which mate, the caterpillar is the 'larva' which will turn into a pupa before it emerges, that's most likely what these were doing, finding a safe place to pupate.

It could be a Buckeye,

http://bugguide.net/node/view/...

Please don't eradicate them.

Thanks Janet. I thought you might know.

Betsy,

with Janet, please don't eradicate.
Buckeyes are beautiful butterflies.

I think it is the Salt Marsh Moth caterpillar we have them here too. The larva varies in color.

http://www.discoverlife.org/mp...

Sorry Josephine, that cat doesn't have branched spines and it has orange spots. All cat larvae vary throughout development.

http://www.discoverlife.org/mp...

https://www.google.co.uk/searc...

Well, maybe it is not Salt Marsh, but the way she describes is how the moth caterpillars behave, the Buckeyes don't come in those large numbers, that I know of.

@mellielong Maybe Melanie will know what the caterpillars are.

Strange things do happen these days it seems; last year we had so many caterpillars in the trees that the ground was black with a coating of castings everywhere. We had large amounts of butterflies last year too, various kinds. This year we have more birds around than I ever remember, but not so many bugs Mother Nature is wonderous.

" Mother Nature is wonderous." She is indeed!

Well, I'm no expert on Texas caterpillars because frankly, you guys get a LOT of different kinds of stuff out there but I would lean toward a moth of some kind. Hard to tell how big they are from the photo, though. I'd say if they're not eating all your plants down to the stem or covering your house, just leave them alone. That being said, every so often we get invaded by Tussock moths here at my house and they do eat anything and they do build little cocoons all over the house, the boat, the travel trailer, etc. I just go around the house, knock them to the ground and step on them. I can't afford to use chemicals because I could possibly kill all my good caterpillars. Or if you're squeamish, you could knock them into a bucket of water (some may still manage to climb out so watch them).

Oh and like Janet said, caterpillars don't mate - they wait until they're in adult form to do that (butterfly or moth). They probably are looking for a place to build their pupa. So unless they're covering your house - and I've totally been there - I'd just leave them alone. Or maybe you could compromise and leave a few to keep the population going.

I've left them alone --- they kinda disappeared now.

Have you noticed an increase in moths? Some moths can take a while to come out and don't come out all at once so it's possible you wouldn't even notice them.