These are boxelder bugs that crawled into cracks and crevices on the exterior of your home last fall. They are now emerging into the warmth of your home, thinking it is spring. As it warms up outside, they will head in that direction to start another summer cycle then head back to your home in the fall.  They are harmless so there is no need for pesticides.  Use a vacuum cleaner.

see here

I get swarmed with those every year (no, not the ant thing from Twilight Zone) and I get the best kicks out watching my three cats make mincemeat of them.

If that was my house, i wouldve killed them with a flamethrower the first time

<- has a phobia on bugs

KM,

Pauls42 is correct they are harmless. I first saw them when I lived in a small apartment building years ago where the box elder bugs would congregate on the front door it was kind of gross and they were all over the entry hallway as they got inside when the door was opened 

I've had further experience with them in my current job where people in the town come to the Village Hall where I work complaining about them. They prefer box elder trees (apparently a tree that does well in swampy areas near water) but will feed/sit on other trees as well. I've read quite a bit on them because of the job and you can use a mild soap and water mixture to kill them as well as the handy vacuum cleaner. They will keep coming back each year as they tend to find a spot they like where the can sit in the sun during the spring and fall.

There's ton of information about them on the net if you look around for it. Good luck.

Brian