What's the mystery near these bugs?

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).

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!
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