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Mole-Limbed Wormlizards: Bipedidae

Two-legged Wormlizard (bipes Biporus): Species Account

Physical characteristics: Colored very pale pink or orangish-pink, and sometimes with a whitish belly, the two-legged wormlizard has two front legs, each with five claws. Adults can reach 7.5 to 8.3 inches (19 to 21 centimeters) long, including a short tail. The tail looks much like the rest of the body but actually begins at the vent, a slit-like opening on the underside of the animal. In this species, the tail is about one-tenth as long as the rest of the body. In other words, a 7.5-inch-long (19-centimeter-long) wormlizard has a tail about 0.75 inches (1.9 centimeters) long. It is a thin animal, and at the middle of its body, it only measures about one-quarter of an inch (6 to 7 millimeters) across.

Geographic range: It makes its home along the western side of the Baja California peninsula in Mexico.

People rarely see these wormlizards, unless they happen to turn over a rock, a pile of leaves, or some other hiding spot where one is lying. (Illustration by John Megahan. Reproduced by permission.)

Habitat: The two-legged wormlizard lives underground in sandy soils usually around the roots of certain shrubs called mesquite (mess-KEET). Their tunnels are usually very shallow—less than an inch (2.5 centimeters) deep—but they sometimes drop to about 6 inches (15 centimeters) under the surface.

Diet: They search underground for ants, termites, and the larvae (LAR-vee) of insects to eat. Larvae are newly hatched insects that usually have soft bodies. Grubs, for example, are the larvae of beetles. At night, they also look for food, including insects and spiders, above ground.

Behavior and reproduction: These animals stay in their shallow tunnels most of the time. In the mornings, they tend to move up to shallower tunnels, then go deeper as the day warms up. Scientists believe that they also search for warm or cool spots underground by moving into the open where the sun beats down to heat up the sand, or under chillier shady areas beneath shrubs or trees. They will leave their tunnels and come up to the surface sometimes, especially at night, to hunt for invertebrates. They are not speedy, graceful animals. Rather, they move slowly and clumsily, sometimes swinging around their front legs in an overhand swimming type of motion. Like other members of this family, the two-legged wormlizard can drop its tail if it is attacked. They squeeze muscles around a weak spot in the tail bone, and the tail drops off. The wound heals, but the worm lizard cannot grow a new tail.

The females lay one to four eggs in July, which is a very dry time in their habitat. The eggs hatch about two months later, just as the rainy season starts and food for the young becomes more plentiful. In the summer after the females reach their fourth birthday, they are old enough to have young of their own. Some scientists think that females may only have young once every other year. Only more research will say for sure.

Two-legged wormlizards and people: People rarely see one of these wormlizards, unless they happen to turn over a rock, a pile of leaves, or some other hiding spot where one is lying. The wormlizard usually responds by quickly slipping into a nearby tunnel and disappearing.

Conservation status: This species is not considered endangered or threatened. ∎



Burnie, David, and Don Wilson, eds. The Definitive Visual Guide to the World's Wildlife. New York: DK Publishing, 2001.

Gans, C. Biomechanics: An Approach to Vertebrate Biology. Philadelphia: J. B. Lippincott Company, 1974.

Halliday, Tim, and Kraig Adler, eds. The Encyclopedia of Reptiles and Amphibians. New York: Facts on File, 1986.

Mattison, Chris. Lizards of the World. New York: Facts on File, 1989.

Schwenk, K. Feeding: Form, Function, and Evolution in Tetrapod Vertebrates. San Diego: Academic Press, 2000.

Vanzolini, P. E. Evolution, Adaptation and Distribution of the Amphisbaenid Lizards (Sauria: Amphisbaenidae). Ph.D. diss. Harvard University, 1951.

Web sites:

"Family Bipedidae (two-legged worm lizards)." Animal Diversity Web. University of Michigan Museum of Zoology. http://animaldiversity.ummz.umich.edu/site/accounts/classification/Bipedidae.html (accessed on December 1, 2004).

Additional topics

Animal Life ResourceDinosaurs, Snakes, and Other ReptilesMole-Limbed Wormlizards: Bipedidae - Physical Characteristics, Habitat, Diet, Behavior And Reproduction, Two-legged Wormlizard (bipes Biporus): Species Account - GEOGRAPHIC RANGE, MOLE-LIMBED WORMLIZARDS AND PEOPLE, CONSERVATION STATUS