Eating my garden in Southern Ontario (Canada)

They are eating the leaves on my zuchini plants at an alarming rate, and there's lots of them. I hope they don't spread all over.

I've seen insects of a somewhat similar shape and look, but never these specifically. Also, I took photos of what I believe to be their eggs, which were found on the underside of the leaves. When I flipped the leaves over there were so many of these insects, and of various sizes too.