Identify a Trapdoor Spider

Trapdoor spiders (family Ctenizidae) build silk-lined burrows in the ground with trapdoor covers made of soil and vegetation. When the spiders feel vibrations caused by passing prey, they will leap out, capture the prey and take it down into the burrow. The variety of burrowing species makes correct identification difficult, but understanding some common features and habits will give you general idea of how to determine if you have come across a trapdoor spider.

Steps

Identifying a Trapdoor Spider

1. Take note of the spider’s length. Trapdoor spiders are approximately 0.79 in to 1.26 inches (1 to 3 cm) long. That means roughly between the size of your pinky nail and your thumbnail.
2. Look at the spider’s body. Trapdoor spiders are black or brown, with stout bodies and legs. Some species have paler color markings, or they may have a silky covering of hair. Their bodies are divided into two sections: the thorax (containing the head and legs) and the abdomen. The abdomen is typically lighter and a slightly different color.
   • Though they may be difficult to see because of its small size, a trapdoor spider will have 6 eyes arranged in 3 groups, whereas most other spiders have 8 eyes.
   • Trapdoor spiders are relatives of tarantulas, but are less hairy, and have smaller, shinier bodies.
3. Watch the spider’s jaws move. The jaws of a trapdoor spider are attached to the front of its head. They move up and down, unlike most other spiders, whose jaws move side to side.
4. Look for gender differences. Females trapdoor spiders are larger than the males, but you will seldom see females because they rarely leave their burrows. Therefore, if you see a trapdoor spider, it is most likely a male. Look for these characteristics that identify male trapdoor spiders:
   • Short and blunt spinnerets. These produce silk, and are located at the tip of the abdomen.
   • A double spur about halfway along their front legs.
   • A dusty or dull carapace (a harder area covering much of the thorax) that is lightly covered in bristles.
   • Pedipalps (small appendages near the jaws) that resemble boxing gloves.
5. Expect variations. There are numerous varieties of trapdoor spiders, each with slightly different physical characteristics. More varieties of trapdoor spiders are still being discovered. If you think you have seen a trapdoor spider, look up the specific varieties that live in your area, so that you know can what kind of specific markings to expect.

Recognizing Trapdoor Spider Habitats

1. Know where trapdoor spiders are found throughout the world. The geographic distribution of trapdoor spiders is erratic and is attributed to the continental drift. Various species of trapdoor spiders can be found all over the world. Look for trapdoor spiders in:
   • North America: Canada, The United States (southeastern and pacific states, and north to Colorado)
   • Central America (Guatemala, Mexico, etc.)
   • Asia (China, Japan, Thailand, etc.)
   • South Africa and Madagascar
   • Australia
2. Look for areas where trapdoor spiders like to burrow. Throughout the world, trapdoor spiders favor warm environments, such as temperate forests and deserts. They will burrow in grassy areas, hillsides, and dirt embankments.
3. Recognize the signs of a trapdoor spider burrow. Trapdoor spiders burrow in the ground (about 0.75 inches wide and up to 8 inches deep) and cover their burrow with a silken hinged “trapdoor” camouflaged by sticks, pebbles, and other natural material. Because the burrows are camouflaged, they can be very hard to see.
   • Larger burrows may have multiple trapdoors.
   • Usually, the burrow faces sunlight and will be found near vegetation.
4. Look for trapdoor spider food. Trapdoor spiders are shy, may be nocturnal, and are rarely seen far from their burrows (males may wander during mating season, however). You might be able to spy one, however, when it eats. The spiders will wait in their burrows until they sense vibrations in the ground caused by insects (including crickets, moths, beetles, and grasshoppers) and other spiders. Then, the spiders will leap out of the trapdoor, grab one of these animals, and drag it back into the burrow.

Tips

• Some trapdoor spiders can live up to 25 years.
• Generally, trapdoor spiders are not aggressive. However, when cornered they may attempt to protect themselves. They may bite, and cause some irritation, but their venom does not appear to be dangerous to humans.
• Since the trapdoor at the entrance to a burrow is covered with plant and soil material and is very difficult to see, it is wise to wear gloves if you are clearing foliage.

Warnings

• Identify-a-Funnel-Spider and Identify-a-Mouse-Spider are often mistaken for trapdoor spiders.

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