What's the mystery near these bugs? I must have a pest of some sort in my house. ...

I must have a pest of some sort in my house. In one room surrounded by our house, right under the windows, we other have dead ants or small poop-looking bumps...never any live ants. These are adjectives along the wall that is under the window. We have no pets, and we are not sure what this could be. I would put out ant killers, but the ants are found already motionless. I just keep vacuuming the vestiges up, but I should really find out what is going on here. Any ideas? (I live in Houston, TX, and we own lots of gecko lizards around).
Flatten hillside to install swimming pool?
Answers:    one possibilty when finding dead ants is that they have newly swarmed an what you are seeing are the males who die shortly after a swarm.

Have you seen any wings? (the wing normally fall past its sell-by date the drones before they die, so don't expect the dead ones to hold wings attached.)

good luck!