These nymphs had just recently hatched from the empty white eggs and were clustered together on the back of a leaf. They are invasive brown marmorated stink bug nymphs. I assume they cluster together to make themselves look like a larger organism to potential predators. Unlike caterpillars and some other "baby" insects, these nymphs don't eat their eggshells. But, with a piercing mouthpart, I guess that would be pretty hard to do!