They are boxelder bugs. I don't think they usually do too much damage.

http://www.extension.umn.edu/garden/insects/find/boxelder-bugs/

Your or a neighbor has a box elder elm tree nearby.

You can kill them with soapy water, even a small amount of dish soap.

It's actually kind of interesting how they seem to be killed by it, though in the grand scheme of things, it's kind of sad to see also. I'm not sure if contact with the water kills them or if it gets into their body quickly through some process, or even if they inhale it/swallow it since it's quite a big drop of water landing on them.

These guys feed almost entirely on maple species, primarily box elder (Acer negundo) and the female seed-bearing trees at that. They tend to be more of a nuisance factor than a real pest.

Just close your windows and doors...your plants will be alright :)
Whatever you do, don't crush any....they stink LOL~

We get boxelder bugs every year. They usually congregate on the warm side of the house. They're here in spring and then kind of fade away, doing no harm that I can see.

One time one got inside, and my cat ate it before I could stop her. Her mouth foamed up a bit, and it seemed unpleasant. So avoid eating one, lol.