trap-door spider, spider of the same family as the native American tarantula. Trap-door spiders dig burrows, which they line with silk and protect by constructing one or two circular, hinged trap doors. The spiders emerge through the snug-fitting camouflaged doors to search for prey. Usually the burrow entrance has a door, the outer surface of which is camouflaged to blend in with the surrounding terrain. If a second door is present, it is usually below the entrance door. Trap-door spiders are classified in the phylum Arthropoda, class Arachnida, order Araneae, family Ctenizidae.