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14.1: Bothriocyrtum californicum: Trapdoor Spider

Difficulty Level: At Grade Created by: CK-12

Common Name

  • California Trapdoor Spider


The trapdoor spider was once very common in Southern California but became less common due to loss of habitat. It can measure from 0.79 in. to 1.26 in. long and is black, brown, and yellow in color. They resemble tarantulas but with smaller, shinier bodies.

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Class: Arachnida
  • Order: Araneae
  • Family: Ctenizidae
  • Genus: Bothriocyrtum
  • Species: B. californicum


The trapdoor spider lives in grassy areas, hillsides, and dirt embankments. They’re range is the southern half of the U.S. from Virginia, south to Florida, and then west to California. The spider builds it’s burrow underground. The length of a trapdoor spider’s burrow can range from 2.5 cm. to 5 cm. Larger burrows have multiple entrances, and the spider will cover each entrance with a door that opens and closes on a hinge of silk. The burrow usually faces directly into sunlight and is near vegetation.

Cell Biology

Trapdoor spiders have eukaryotic cells. Eukaryotic cells contain a nucleus and many other organelles. An organelle is a special subunit within a cell that has its own function. Cells in a species can divide through two ways: mitosis and meiosis. Mitosis is the entire process of cell division including the nucleus and the cytoplasm. Meiosis is the process of cell division in a sexually reproducing way that reduces the number of chromosomes in reproductive cells. Through the process of meiosis, the trapdoor spider makes sperm and eggs that have half the chromosomes of the original cell. Chromosomes are made of DNA, which has genes with codes for the spider’s traits.


The spider has been evolving for at least 400 million years. Their ancestors were more crab-like in appearance. The spider’s use of silk has also evolved with the changing plant and insect population as well. The silk may have originally been used as a protective covering for eggs, but later utilized as a home and a tool for hunting by species like the trapdoor spider.


The trapdoor spider eats small insects and other smaller spiders. Female spiders will capture their prey and regurgitate it to feed their spiderlings. Enemies of the trapdoor spider include certain kinds of spider wasps. The wasp will sting the spider, inserting its eggs into the spider’s body. When the eggs hatch, the larvae will eat the spider alive.

In the fall, the male leaves its burrow to look for female spiders for mating. The female, however, never travels far from her burrow, especially if she has an egg sack.

Anatomy and Physiology

Trapdoor spiders are a medium-sized spider. The spider has a bulky body and legs. They have large venom glands that have been known to be harmful to humans. They also have special spines on their jaws called a rastellum that help them dig their holes. As with many spiders, the female trapdoor spider is larger than the male and can lay up to 10,000,000,000 eggs at a time.


The trapdoor spider is a solitary spider. It digs the hole that it hides in 6-7 inches deep into the side of a hill using its fangs, and then lines the inside if it with silk. It makes the “trapdoor” part of the hole with saliva, dirt, and silk. They have poor eyesight, so they rely on the vibrations that an insect causes when it walks by. It is non-aggressive in general but will hold its ground when cornered.




  • Gaven Springer
  • Orion Silva

Supervising Faculty

  • Amy Huff Shah


  • Museum School, San Diego, California

Image Attributions




6 , 7 , 8 , 9 , 10 , 11 , 12

Date Created:

Aug 15, 2012

Last Modified:

Dec 05, 2014
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