This morning I took 30 of these buggers off one little tree--all the tree's new growth had been skeletonized before I saw them. These caterpillars become a brown night-flying moth. Judging by my yard, the moths are prolific reproducers.
The caterpillars are a major pest for Texas Mountain Laurels--they can defoliate a tree if left unchecked. Birds don't eat them because of the alkaloids absorbed from the plants. The only natural enemies I've seen (besides my fingers) have been fire ants and assassin bugs, but your tree may not survive a combo of genista and drought while you wait for assassin rescue.
The caterpillars look hairy (easier to see in the picture if you look at the background caterpillars) but don't sting. If you're finicky, wear gloves.