Redback Jumping Spider

Redback jumping spiders (Phiddippus johnsoni) are common in California. It is one of the most often encountered jumping spiders in North America.

Many people believe that the redback jumping spider is particularly dangerous to humans due to its red back which is definitely not the case. The name Johnson Jumper has been suggested as an alternative, and as it a jumping spider, the name is probably less confusing.


Redback jumping spiders prefer to stay in their tubular, silky nests beneath debris, wood, or anywhere undisturbed on the ground. Since the redback jumping spider is a sight hunter, it stays in its nest during nights and when the conditions for seeing prey are poor.


They eat prey almost up to their own size. The average size of their prey is, however, about half their own size. They feed on a number of different invertebrates, such as caterpillars, moths, and flies. They also eat spiders, most in the form of the larger females eating males.


Jumping spiders are hairy and grow to approximately three quarters of an inch in length. The size of individual spiders shows great variability. The back of a Johnson spider is distinctly red, with a black strip if it is a female. The rest of the body is usually entirely black.


The bite from a redback jumping spider isn't fatal. The bite results in swelling and pain at the bite site. The pain and swelling usually lasts for several days. Some people experience other symptoms as well from a redback jumping spider bite. The spider belongs to the Salticidae family.

The jumping spider is not considered as dangerous as many other spiders since its venom is not as toxic as, for instance, the venom of black widows. Bacterial infections around the site of a wound should, however, be avoided at all costs.

Life Cycle

Before mating, the male walks toward the female, then backs away. He performs a kind of zigzag dance, and some males are reported to produce a sound by twitching their abdomens while dancing. Sometimes the male is killed after mating. This behavior is referred to as sexual cannibalism.

A Typical Sight Hunter

Phidippus johnsoni is a typical sight hunter—both when it comes to prey and mating.

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