They are bugs, Aphids to be more precise. In my location, this sort of thing happens here or there, in one year or another, on this plant or that. It's intermittent and likely won't happen again for a while. I don't really do anything about it. Your location may vary. Some people like to spray them off with a jet of hose water. Other people use soap solutions to kill them. As far as preventing them next year, just keep your eyes peeled and when you see them then Google for "aphid control" and pick your favorite method. These things blow in the wind like dust so you can't prevent their arrival, but you can contain them once they arrive.

Thanks! I'm guessing not all aphids look the same. I've only knowingly dealt with the green ones on my roses! Again, I appreciate your response. It was encouraging!

yeah I'm in the Dallas area... Most of the time when I grow squashes late in the season, they do avoid most of the SVB and squash bugs, but do get hit hard by aphids and powedery mildew pretty bad. I have tried spraying with water, but most of the time the problems with the aphids eventually takes care of itself naturally. I had a big infestation in September, but I noticed ladybug larva, hoverfly larva, lacewing larva, and parasitic waps (Google "aphid mummies") all making their appearance, and the all eventually catch up and eventually bring the aphids under control. Its the powdery mildew that's been doing most of the damage recently on my plants :(