Great question Ken and timely as well. What you are seeing are Boxelder Bugs in their larval stage. They begin their development in a reddish color that finally turns dark brown or black with red trim at maturity. They suck the juice from young leaves, but have no specific plant of choice. 
   They are mostly a pest type problem outdoors that should not require any chemical treatment. The biggest concern with Boxelder Bugs is they like to move indoors in the fall and while they do no damage, they are quite a nuisance issue when that occurs.
   I find quite a few in our back yard every summer and the best control I have found is just to disturb their location. Stir up mulch if that is where you see them or hit them with a blast from the hose if they are on plants. Once disturbed, they will generally move to a new location.
   Here is a link from the University of Maryland Extension on Boxelder Bugs giving you additional information: https://extension.umd.edu/resource/boxelder-bugs/
   Once again, thank you for your question and have a great summer.