The picture on my end is a little fuzzy, so hard to see details. But it appears that these are a type of aphid. See the website below for pictures and further description to see if these are consistent with the insects you are seeing. http://www.extension.umn.edu/garden/insects/find/aphids-in-home-gardens/ Aphids suck plant sap. With some plants, and when in large numbers, these can damage the plants. An easy method for control is to spray them off the plants with the hose. Additional information is in the link above.