Wikijunior:Bugs/Tarantula

What does it look like?
These fierce-looking spiders belong to the Family Theraphosidae. They are the largest spiders in the world, with about 750 species worldwide. Tarantulas have been on earth for more than 150 million years.

Most tarantulas are black or brown. Those of North America are usually brown. In other parts of the world, they are more colorful with blue, orange, or yellow markings. The Indian ornamental tarantula has yellow fangs. Its legs are grey-and-black striped on top and yellow-and-black striped underneath. The Pink-toed Tarantula has a dark grey body with pink at the ends of the legs. The Mexican Red-Knee Tarantula has patches of orange and red on its legs. The Steely-Blue Tarantula is an iridescent purple.

Some tarantulas are only 1 inch long. Others are as long as 4 inches. In North America, they reach about 3 inches. Leg span varies from 3 to 12 inches. Each leg has 2 claws at the tip. Arboreal (tree-dwelling) tarantulas have thick brushes of hair at the end of each leg, so they can climb on smooth leaf surfaces. The Goliath bird-eating spider (Theraphosa blondi) is the largest tarantula species of all. It can have an 11-inch leg span and weigh as much as 6 ounces.

Tarantulas have two major body parts—the prosoma and the abdomen. A waist-like connection (pedicle) allows the two parts to move independently. They have a thick covering of hair and tiny bristles on the abdomen.

There are 8 closely grouped eyes—2 large round eyes in the middle surrounded by 3 eyes on each side.

Most spiders are divided into 2 groups—the Araneomorphae (true spiders) and the Mygalomorphae (tarantulas and their relatives). True spiders have fangs that point sideways. Tarantulas are not true spiders because their fangs point straight down like those of a snake.

Where does it live?
Tarantulas of North America, South America, and Australia are called New World tarantulas. Those of Europe, Asia, and Africa are called Old World tarantulas. The rainforests of French Guiana, just north of the equator, are home to about a dozen species of tarantulas. Many tarantula species live in tropical regions. Others live in warm, dry desert areas. Their natural habitat varies, ranging from savannas and grasslands to rainforests and mountains. In rainforests, tarantulas build burrows in spreading tree roots and bromeliads. Some types of tarantulas live in burrows beneath the ground and some live in tented treetop shelters.

The Goliath Bird-eater is found in North America. It is native to the rain forests of northern South America. It makes its home inside deep burrows in marshland or swamps.

The Pink-toed Tarantula is found in the Amazon Basin and on Caribbean islands. It climbs banana trees to nest in folded leaves. It sometimes makes a home in a palm- thatched roof or the hollow center of a pineapple plant.

What does it eat?
Tarantulas eat insects and other arthropods. Arboreal tarantulas hunt for food above ground. Ground-dwelling tarantulas hunt on or near the ground. Instead of spinning webs to catch prey, tarantulas use ambush as their primary method of capture. They grind up their food with teeth behind their fangs.

The Pink-toed Tarantula eats insects and tree frogs. The Western Desert Tarantula preys on lizards, crickets, beetles, grasshoppers, cicadas, and caterpillars. Very big tarantulas kill mice and lizards and even birds.

Despite its name, the Goliath bird-eating spider prefers small lizards, frogs, and insects to birds.

How does it defend itself?
Tarantulas have many enemies. They are food for birds, reptiles, amphibians, and other tarantulas. The hairs covering their body alert them to vibrations. If disturbed, tarantulas adopt a “threat” posture. They raise the front half of the body, hold the legs high in the air, and ready the jaws for action.

Since they are arthropods, they rely on an exoskeleton for protection. They are most vulnerable while molting because they are fragile and cannot move. A smaller insect can easily kill a tarantula while it is molting.

Snakes and birds are enemies of the Western Desert Tarantula. In Eurasia, mongooses dig tarantulas from burrows. Tarantulas can release stinging hairs from their legs to irritate the skin of an attacker. New World tarantulas use urticating (hooked or barbed) hairs as a defense. When threatened, some species kick these tiny, sharp hairs off their back end. Each hair is covered with tiny barbs and is light enough to float on air. Other species deliver the hairs through direct contact. The hairs cause an animal’s skin to become itchy and sore. Old World tarantulas do not have urticating hairs. When threatened, the Goliath Bird-eater makes a hissing sound with its back legs by rubbing the bristles together. It flicks urticating hairs from its abdomen. The hairs cause painful rashes on humans. The bite is not very toxic but it causes pain, nausea, and sweating.

The most vicious predator of tarantulas is the female tarantula hawk. Its body can be up to 2 inches long and its stinger can be 1/3 of an inch long. Upon entering the burrow, the tarantula hawk paralizes the female tarantula with its sting, then drags her away to be used as food for larvae. There is no defence against this enemy.

What stages of metamorphosis does it go through?
The Mexican Red-Knee Tarantula grows extremely slowly. A female has a life span of around twenty years. She lays a clutch of 100 to 600 eggs. After hatching, the spiderlings molt every 2 weeks for the first few months. Molting is less frequent as they mature. They reach maturity at around 5 years of age. When fully grown they molt about once a year.

The Western Desert Tarantula may take 10 years to reach maturity. A female lives a long time, but a male usually lives only 2 to 3 months. Eggs hatch in about 7 weeks. The young spiderlings cut holes in the silk covering and disperse right away to escape being eaten by their mother. Most spiderlings fail to reach maturity because they are eaten by predators or cannot find enough food.

The female Goliath Bird-eater always mates, but eventually kills her mate. She lays a clutch of 100 to 200 eggs. The eggs are stored in the burrow for about 6 weeks. Spiderlings hatch in about 2 months. They stay in the nest at first, then molt and disperse. Females mature in 3 to 4 years and have an average life span of 15 to 25 years. Males die soon after maturing and have a life span of about 3 to 6 years.

What special behavior does it exhibit?
Tarantulas are active at night and hide in dark cavities or burrows during the day. They emerge to hunt in the dark. They use their sense of touch to find prey.

Urticating hairs are used to mark territory and to protect burrow entrances, cocoons, and egg sacs.

Tarantulas have their sense of smell in their feet and use special hairs on their feet and legs to taste things.

They can re-grow lost legs. Sometimes they will pull off an inured leg and eat it.

How does this bug affect people?
Tarantulas attack humans only if provoked. They would rather hide. The bite of a North American tarantula is not very dangerous. People report it is similar to the sting of a wasp or bee. However, the bite can be fatal to a person who is allergic to the venom. Some South American species have deadly venom. The venom of the Indian ornamental tarantula is among the most dangerous to humans.

Some people roast tarantulas to burn the hairs off, then enjoy them as a snack. Sometimes the cooked leftover fangs are used after the meal as a tooth pick.

The Mexican Red-Knee Tarantula is native to parts of Central America. It has become endangered due to habitat destruction and pet-trade collection. It is one of the few arthropods protected under CITES laws (International Convention of Trade in Endangered Species).