There are around 128 species in this family, 14 in North America and 10 in the US. They are usually dark coloured, and spend most of their lives in their burrows. They have medium to large sized bodies, but shorter legs than you'd expect for a spider of their size, giving them a stocky appearance. They are mainly nocturnal, have eight eyes and do not make webs.
The trapdoor (see the photograph below) is constructed of a mixture of the surrounding soil and vegetation held together by silk, making it very well camouflaged. The door would lie at surface level; the photograph below shows one that has been dug up along with the burrow, and there is a glass rod holding the door partially open.
The spider may lay down trip lines radiating from the side of the trap door. It lives inside a silk-lined burrow. To catch its prey it hangs on to the inside of the door, then when it detects movement from vibrations or the breakage of a trip line, it darts out of the burrow to capture the prey. Prey items include insects, small frogs, baby birds, small snakes and mice. A starving trapdoor spider may rest partially outside its door.
Their main predators are spider wasps in the Pompilid family.
Mating. A male will leave his burrow to find a mate, females rarely leave their burrow. A male approaching a female in her burrow can probably be detected by her. It is not yet known how the males manage to overcome the female's killing instinct long enough for mating to take place.