Tarantulas, Family Theraphosidae

Habits and Traits of Tarantulas

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Tarantulas look big and scary, but they're actually rather docile and virtually harmless to people. Members of the family Theraphosidae exhibit some interesting behaviors and share certain traits.

Description

Chances are, you would recognize a tarantula if you came across one, without knowing much at all about the traits that define it as a member of the family Theraphosidae. People recognize tarantulas by their enormous size, relative to other spiders, and by their conspicuously hairy bodies and legs.

But there's more to a tarantula than hair and heft.

Tarantulas are mygalomorphs, along with their close cousins the trapdoor spiders, the purse-web spiders, and the folding-door spiders. Mygalomorphic ​spiders have two pairs of book lungs, and large chelicerae bearing parallel fangs that move up and down (rather than sideways, as they do in araneomorphic spiders). Tarantulas also have two claws on each foot.

See this diagram of the parts of a tarantula for more information about the tarantula body.

Most tarantulas live in burrows, with some species modifying existing crevices or burrows to their liking, and others constructing their homes from scratch. Some arboreal species climb off the ground, living in trees or even on cliffsides.

Classification

Kingdom – Animalia

Phylum – Arthropoda

Class – Arachnida

Order – Araneae

Infraorder - Mygalomorphae

Family - Theraphosidae

Diet

Tarantulas are generalist predators.

Most hunt passively, by simply lying in wait near their burrows until something wanders within reach. Tarantulas will eat anything small enough to catch and consume: arthropods, reptiles, amphibians, birds, and even small mammals. In fact, they'll even eat other tarantulas given the opportunity.

There's an old joke that tarantula keepers tell to illustrate this point:

Q: What do you get when you put two small tarantulas in a terrarium?
A: One big tarantula.

Life Cycle

Tarantulas engage in sexual reproduction, although the male transfers his sperm indirectly. When he's ready to mate, the male tarantula constructs a silken sperm web and deposits his sperm there. He then sucks the sperm back up with his pedipalps, filling special sperm storage organs. Only then is he ready to find a mate. A male tarantula will travel at night in search of a receptive female.

In many tarantula species, the male and female engage in courtship rituals before mating. They may dance or drum or quiver to prove their worth to one another. When the female appears willing, the male approaches and inserts his pedipalps into her genital opening, and releases his sperm. He then quickly retreats to avoid being eaten.

Female tarantulas usually wrap her eggs in silk, creating a protective egg sac which she may suspend in her burrow or move as environmental conditions change. In most tarantula species, the young emerge from the egg sac as bald, immobile postembryo, which require a few more weeks to darken and molt into their first instar stage.

Tarantulas are long-lived, and typically take years to reach sexual maturity.

Female tarantulas can live 20 years or more, while the male's life expectancy is closer to 7 years.

Special Behaviors and Defenses

Although people often fear tarantulas, these big, hairy spiders are actually quite harmless. They aren't likely to bite unless mishandled, and their venom isn't all that potent if they do. Tarantulas do, however, defend themselves if threatened.

If they sense danger, many tarantulas will rear up on their hind legs, and extend their front legs and palpi in a kind of "put up your dukes" posture. Although they don't possess the means to inflict much damage on their attacker, this threatening posture is often enough to spook a potential predator.

New World tarantulas employ a surprising defensive behavior – they fling urticating hairs plucked from their abdomens at the offender's face.

These fine fibers can irritate the eyes and respiratory passages of predators, stopping them in their tracks. Even tarantula keepers need to be cautious when handling pet tarantulas. One tarantula owner in the UK was surprised when his eye doctor told him he had dozens of tiny hairs lodged in his eyeballs, and they were the cause of his discomfort and light sensitivity.

Range and Distribution

Tarantulas live in terrestrial habitats throughout the world, on every continent except Antarctica. Worldwide, about 900 species of tarantulas occur. Just 57 tarantula species inhabit the southwestern U.S. (according to Borror and DeLong's Introduction to the Study of Insects, 7th edition).

Sources

  • Bugs Rule! An Introduction to the World of Insects, by Whitney Cranshaw and Richard Redak
  • Borror and Delong's Introduction to the Study of Insects, 7th edition, by Charles A. Triplehorn and Norman F. Johnson
  • Tarantulas and Other Arachnids: Everything About Selection, Care, Nutrition, Health, Breeding, Behavior (Complete Pet Owner's Manual), by Samuel D. Marshall
  • The Natural History of Tarantula Spidersby Richard C. Gallon. British Tarantula Society website, accessed online December 26, 2013.
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Hadley, Debbie. "Tarantulas, Family Theraphosidae." ThoughtCo, Apr. 19, 2017, thoughtco.com/tarantulas-family-overview-1968556. Hadley, Debbie. (2017, April 19). Tarantulas, Family Theraphosidae. Retrieved from https://www.thoughtco.com/tarantulas-family-overview-1968556 Hadley, Debbie. "Tarantulas, Family Theraphosidae." ThoughtCo. https://www.thoughtco.com/tarantulas-family-overview-1968556 (accessed May 23, 2018).