I think? it's a brown tersa sphinx moth caterpillar. They go underground to make their pupa, and, by the dark color of its head, that might be what it wants to do. Their natural host plant is buttonweed, but they commonly use pentas in people's gardens.

Here's an old picture of a brown one and a green one -

{{gwi:334939}}

Sherry

Very cool caterpillar and the moth is cool too. Found one once on my hardwood dining room floor of all places! How wonderful that your kids bring you bugs!! :)