So yesterday afternoon I was walking by the tomato plant; the one with the treehoppers and their eggs on it. And I noticed the eggs had hatched. There were several to many tiny black treehopper nymphs stationed slightly apart from the parents, their sucking mouthparts inserted into the tomato stem, tapped into the nutrient stream in the tomato's phloem.
This afternoon, I counted 17 nymphs per each adult female. They will stay close through their development stages; these groups are called aggregations. When I nudged one of the adults away from the egg-laying site, she just sidled back over the eggs, so maybe there are still more to hatch.
I picked the first little tomato from this plant today. It was tasty.