San Diego Natural History Museum--Your Nature ConnectionSDNHM Field Guide
Photo of a tarantula: a large, brown, hairy spider.

Aphonopelma
Tarantula

THERAPHOSIDAE

Description

Tarantulas are large, hairy spiders, with a leg span that may be as wide as 5 or 6 inches. Despite Hollywood's deadly and aggressive image of the tarantula, the truth is that San Diego County's three resident species of the genus Aphonopelma are actually quite docile. Both males and females are capable of inflicting a bite when threatened, but they rarely do so and their venom is considered non-toxic to humans.

A conspicuous bald spot may be seen on the abdomen of many tarantulas. This results from the spider's defensive behavior against its vertebrate enemies. When confronted, the spider will rub its hind legs over its body, brushing off irritating hairs into an enemy's eyes. These hairs are replaced during each successive moult.

Range and Habitat

Common to the local desert and low-elevation chaparral habitats, tarantulas can also be found in many of the city's undeveloped canyons. They are not normally encountered during the day and generally remain hidden in abandoned rodent burrows or other suitable tunnels that they line with silk. Tarantulas become active in the late afternoon from spring through fall.

Natural History

Like most other spiders, tarantulas are considered beneficial predators who feed on many invertebrates including sowbugs, pillbugs, insects, and even other spiders. Their prey is grabbed and crushed in the tarantula's powerful fangs. Owing to the tarantula's reduced oral opening, or 'mouth,' it secretes digestive enzymes through its fangs to dissolve the prey externally. The spider then sucks the liquefied meal back up through its small mouth and into its digestive system.

The mating and egg laying of tarantulas occur in the fall, with 200 or more eggs hatching the following spring. It takes about four years for a tarantula to reach adult size. Males can live a few more years and some captive females have been known to live 40 years.

The primary enemies of the tarantula, other than rodents and overeager humans seeking new pets, are Pepsis wasps. The female wasps sting and paralyze the spiders, providing a fresh and ready food supply for their offspring.

David Faulkner, Research Associate, Entomology Department

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