Wikijunior:Bugs/Trap-door Spider

What does it look like?

Trapdoor Spiders are 3/8 to 1-1/4 inches long. They have a row of spines on each jaw. They use these spines to dig burrows in the ground. They have 8 eyes. The eyes are close together. They have 4 pairs of legs. They wave the first pair of legs to mimic antennae. Each of the legs has 7 parts. This makes them very agile and fast. There are 3 tiny claws on each foot. A tough outer covering called chiton protects them. Tiny hairs on the body sense vibrations and sounds.

California Trapdoor Spiders are blackish-brown in color. Their abdomen is egg-shaped. Their legs are dark.

Ravine Trapdoor Spiders are brown with a black back. There are grooves on the abdomen.

Brown Trapdoor Spiders are dull brown with pale gold hairs. Males have thick pedipalps (feelers) on the face. These are used when handling and eating prey.

Sigillate Trapdoor Spiders are brown with a glossy outer covering (carapace). There are 4 to 6 hairless spots that make a design (sigil) on top of the abdomen. Their eyes are arranged in 3 distinct rows.

Where does it live?

Trapdoor Spiders are common in the southwestern United States. California Trapdoor Spiders live on high sunny cliffs with areas of hard soil. They make horizontal tunnels up to 8 inches long.

Ravine Trapdoor Spiders are found in Tennessee, northwestern Georgia, and Alabama. They make burrows in steep banks. They like sandy soil covered with leaf litter.

Brown Trapdoor Spiders and Sigillate Trapdoor Spiders live in Australia.

What does it eat?

Trapdoor Spiders eat insects, millipedes, and other spiders. They also eat frogs, mice, and small fish.

How does it defend itself?

These spiders tend to be quite timid. Males may stand up and present their fangs if threatened.

What stages of metamorphosis does it go through?

Males search for females from November to February usually after heavy rain. They mate in the female’s burrow. She lays her eggs several months later and protects them in the burrow. Trapdoor spiders undergo simple, incomplete metamorphosis. There is no larval or pupal stage. There is no “resting” stage. When spiderlings (newborn spiders) hatch from the eggs they look like small versions of adults. In a few months, after spring rains, they disperse on the ground and find a place to make their own burrows. They grow by shedding (molting) the outer covering of the body (exoskeleton). As a spiderling grows it widens its burrow and adds new rims to the door.

Trapdoor spiders take several years to reach maturity and live 5 to 20 years. Females stay inside or near their burrows. Males leave to look for a mate as soon as they are mature.

What special behavior does it exhibit?

Trapdoor Spiders dig tubes in the ground for burrows. They seal the burrow with a hinged lid, or door, made of silk, dirt and debris. Some species make very thin doors, while others make thick doors. The spider holds the door shut with its fangs. When an insect makes vibrations near the door, the spider rushes out, catches it, and drags it into the burrow.

In regions with little rainfall, Trapdoor Spiders use dry leaf litter to disguise the door to their burrow. They make trip lines on the rim of the burrow to signal the presence of prey. Some, like the Brown Trapdoor Spider, do not make doors for their burrows.

How does this bug affect people?

Brown Trapdoor Spiders probably help control garden pests. They are thought to be harmless, but it is best to leave them alone. Trapdoor Spider bites may cause some pain and swelling. Trapdoors are often mistaken for Funnel Web Spiders which have dangerous bites.