Wikijunior:Bugs/Mexican Red-Kneed Tarantula

What does it look like
Mexican Red-Knees are black with patches of red or orange hair on their leg joints. They usually weigh about 1/2 ounce. They are 4 to 5 inches long with a 6 to 7 inch leg span. They have 8 legs made up of 7 parts plus a claw. Each foot has 2 claws.

The dark abdomen is covered with brown hairs. The carapace, a hard protective covering, is creamy beige with a distinctive black square. There are 2 pairs of web-producing organs (spinnerets) on the back side of the abdomen. There are two leg-like organs at the front called palps.

They have 8 eyes located around the head. They can see forward and backward, but only see shades of light and dark.

Where does it live?
Mexican Red-Kneed Tarantulas live along the central Pacific coast of Mexico, from southern Jalisco to north western Oaxaca State. They are found inland to the states of Mexico and Morelos. They do not live in the United States.

Their habitat is coastal land and desert scrubland. They live in rocky areas and rocky outcrops. They burrow at the base of cacti and thorny bushes in deciduous forests. Burrows usually have one entrance just a little wider than the tarantula itself.

What does it eat?
Mexican Red-Kneed Tarantulas are carnivores (meat eaters). They eat insects, lizards, frogs, small birds, and mammals. When an insect or other prey walks across the web, it is ambushed and injected with venom. The venom kills the prey and turns it to liquid so it can be digested. Undigested parts are usually wrapped in a web and moved to another area of the burrow.

How does it defend itself?
Their natural enemies are lizards, snakes, spider-eating birds, and some wasps. They are usually very docile and not aggressive. When threatened, they stand on their back legs. Threatening behavior is used to scare predators away. If provoked, they throw off barbed hairs from the abdomen. Hairs fly in all directions and cause irritation to eyes, skin, and mucous membranes.

What stages of growth does it go through?
Mexican Red-Kneed Tarantulas go through main growth stages: egg, spiderling, and adult. Young spiderlings often look like small versions of adults. They grow by shedding or molting the exoskeleton (outer covering). In the first 4 months spiderlings molt every 2 weeks. Adults molt about once a year.

Spiderlings are able to live on their own at about 15 days old. Males mature about 4 years of age and live about 10 years. Females mature at 6 or 7 years of age and live 25 to 30 years.

Mexican Red-Kneed Tarantulas mate between July and October in the rainy season. After mating, females often become aggressive causing males to flee. After mating, females sometimes try to kill and eat the male. This behavior has not been seen in the wild.

Mature females add extra silk inside the burrow during the reproductive season. They make a webbed carpet extending out from the burrow entrance. They wrap fertilized eggs in a silk egg sac. The egg sac contains one-hundred to six-hundred eggs. Eggs hatch between 1 and 3 months. Spiderlings may remain in the egg sac for 3 weeks after hatching. They spend another 3 weeks in the burrow then disperse.

What special behavior does it exhibit?
Mexican Red-Kneed Tarantulas have 8 legs but only 6 are used for walking. The front 2 are used to capture prey. The ends of the legs are sensitive to movement and help the tarantula detect prey.

Lost legs can be re-grown during molting. The molting process takes several hours. During molting, the old exoskeleton splits open. The tarantula lies on its back and slowly pulls out its entire body including hairs. It is very vulnerable to predators in this state.

How does this bug affect people?
Mexican Red-Kneed Tarantulas benefit people by keeping insect populations in check. They are often seen in Hollywood films.

They make docile and colorful pets. In the wild they are threatened by people who collect them for the pet trade. Many are bred in captivity.

Their bite is painful because they have large fangs. People report the pain is like the sting of a bee or a wasp. The venom can cause an allergic reaction.

They throw barbed hairs when threatened. The hairs can cause skin irritation or a painful rash. Hairs can cause blindness if they hit the eyes.