After lifting up a paver stone and uncovering a pavement ant nest, I found these very small, reddish-brown ants sharing the same galleries. Here they are crawling over cocoons and larvae much bigger than themselves. I don't know whether those are pavement ant cocoons that these smaller ants are raiding, or whether the cocoons are immature queens for the little red ants. I thought they might be Thief Ants from their behavior, but their abdomens look too large and they don't appear to have multisegmented waists. So, I'm not sure what they are.