Lots of fuzzy baby caterpillars here in the lab. Right now these two species look pretty similar, but the differences will start accumulating in the next few instars. Currently they are less than a week old. The first two photos are the babies from this post!

Acronicta hastulifera, second instar

Acronicta hastulifera, second instars

Acronicta americana, second instars (and molting into third)