Phidippus Johnsoni – Red-Backed Jumping Spider

The red-backed jumping spider, Phidippus johnsoni, is found throughout the Western United States and Canada. The spider has a black body and the back of its abdomen is bright red.

Description of the Red-Backed Jumping Spider

The redbacked jumping spider is generally quite easy to identify. It’s body is predominantly black with a brightly red colored abdomen. The abdomen of the smaller male is completely and uniformly red while the female’s back is red with a black longitudinal stripe along the abdomen. Sometimes, there are a few small white or yellow dots on the abdomen and the red area itself is surrounded by a thin yellow or white line.

Male phidippus johnsoni red-backed jumping spider black with red abdomen
The male red-backed jumping spider has a uniformly colored red back. Photo: Wikimedia Commons
female red-backed jumping spider phidippus johnsoni black spider with short legs and red back
Female Phidippus johnsoni with the characteristic black stripe on its red back. Photo: Wikimedia Commons

The spider’s chelicerae (jaws) are iridescent and teal-colored. The red-backed jumping spiders shares this beautiful trait with many other species of jumping spiders.

Red backed jumping spider iredescent chelicerae jaws
A red-backed jumping spider showing parts of its iridescent chelicerae. Photo: Doug Letterman

With its black and red appearance, the red-backed jumping spider mimics the appearance of velvet wasps (mutillid wasps). The exact evolutionary reason behind this mimicry is still unknown. However, it is believed that the appearance should deter potential predators as velvet wasps can deal a painful sting.

Within its range in the Western United States, Phidippus johnsoni can be confused with Phidippus carneus. However, Ph. carneus usually has distinctive white bands around the legs and the white ring around the red coloration on the back is usually thicker in Ph. carneus. Another similar-looking species is Phidippus clarus, which occurs mostly in the Eastern United States.

Size

The red-backed jumping spider is relatively large, compared to other jumping spiders. Females reach an average body length of 0.35-0.55 in. (9-14 mm). Their legs are quite short and their total leg span is just slightly longer than the body size. Male individuals are smaller and reach and average body size of 0.25-0.45 in. (6-11 mm).

Web

Jumping spiders do not spin webs in order to catch prey animals. They are active hunters preying on flies, moths, bugs as well as other spiders. Jumping spiders mainly use their ability to spin silk to spin a “safety line” during their jumps. If the jump fails, the spiders falls into the safety line from where it can climb back to safety.

Bites

The red-backed jumping spider is not an aggressive spider and its first instinct is to run away (or jump away) if humans or animals approach it. In rare occasions, they do bite humans or pets leading to some local swellings or potentially a mild headache. Other known symptoms are not known from the relatively mild venom of jumping spiders.

Scientific Classification of Phidippus johnsoni

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Chelicerata
  • Class: Arachnida
  • Order: Araneae
  • Infraorder: Araneomorphae
  • Family: Salticidae
  • Genus: Phidippus
  • Species: Phidippus johnsoni

Distribution of the Red-Backed Jumping Spider in the USA

The red-backed jumping spider occurs in the Western United States, west of the Great Plains. The spider is especially common in California and is also found in the following U.S. States: New Mexico, Colorado, Wyoming, Montana, Arizona, Utah, Idaho, Nevada, Oregon, Washington.

References

Phidippus Johnsoni – Red-Backed Jumping Spider

5 thoughts on “Phidippus Johnsoni – Red-Backed Jumping Spider

  1. Friend of mine found this spider in her back yard near the rabbit hutch. her location is a couple miles north of the Washington State border in British Columbia Canada. Here are some pictures for identification purposes I cannot seem to be able to post an image

  2. Found a Phidippus Johnsoni, male, in my garage in Fairview Heights, Southern Illinois. I am so afraid of spiders that I kill him without having second thoughts. Sorry. Then I put it in a zip lock bag to be sure I had seen well for at 8:30am when the sun rays hit it was a red, with deep black ” big dented head”, black legs, and measuring close to 1/2 inch.
    It looks exactly as the picture portrayed in : USA Spiders , Phidippus Johnsoni-Red-Backed Jumping Spider .
    PD: I was unable to upload an image
    Silly me… I thought it was a relative to the Black Widow.

  3. I’m in southern Ontario’s Niagara area and took this shot the other day in my living room. It sure looks like a redback, but what’s it doing so far from ours natural range?

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