The red back jumping spider, Phidippus johnsoni, is a small, visually striking arachnid commonly found across North America. Many people encounter these spiders and wonder about their potential danger or if they are harmful to humans. This article provides clear information about the red back jumping spider and its interactions with people.
Identifying the Red Back Jumping Spider
The red back jumping spider, Phidippus johnsoni, is a compact arachnid. Adult females typically measure between 9 to 14.2 millimeters in body length, while males are slightly smaller, ranging from 6.2 to 11 millimeters. Both sexes are characterized by a mostly black body, vibrant teal chelicerae, and a distinct red or reddish-orange patch on their abdomen; the female’s red marking usually features a central black stripe, whereas the male’s is solid red.
These spiders are widely distributed across western North America, extending from northern Mexico up into southern Canada, bounded by the Great Plains and the Pacific Ocean. They inhabit a variety of environments, from coastal dunes and oak woodlands to urban and suburban areas, often found on fences, walls, and in gardens. Unlike many spiders, Phidippus johnsoni does not construct large webs to capture prey, instead using its exceptional eyesight to actively stalk and pounce on insects. Their movement is characterized by sudden, precise jumps, which is a hallmark of the jumping spider family.
Understanding Their Venom
Spiders are venomous, not poisonous; venom is injected through a bite, while poison causes harm if ingested or absorbed through contact. The red back jumping spider, like most spiders, produces venom to subdue its insect prey. This venom contains various chemical compounds designed to immobilize and begin digesting its prey.
Despite possessing venom, the bite of Phidippus johnsoni is not considered medically significant to humans. This means that while they can bite, the effects are typically mild and localized. A bite often results in minor, temporary symptoms such as localized pain, slight redness, or mild swelling at the site. These sensations are frequently compared to the discomfort of a bee sting or a mosquito bite and usually resolve within a few hours.
Severe reactions to a red back jumping spider bite are rare. When they do occur, they are attributable to an individual’s allergic sensitivity to the venom, rather than the venom’s inherent potency. For most people, the venom from a red back jumping spider poses no serious health risk.
If You Encounter One
Red back jumping spiders are not aggressive towards humans and prefer to flee rather than bite when approached. Bites occur only if the spider feels directly threatened or is accidentally pressed against the skin, such as when trapped within clothing.
Should you encounter a red back jumping spider, it is best to observe it from a distance. If it is in an undesirable location, you can gently guide it outside using a cup and a piece of paper. These spiders are beneficial in controlling insect populations, so relocating them outdoors is often a practical choice.
In the uncommon event of a bite, clean the affected area thoroughly with soap and water to prevent infection. Applying a cold compress can help alleviate any localized pain or swelling. Over-the-counter pain relievers may be used for persistent discomfort. Medical attention is not required unless symptoms are unusually severe, continue for an extended period, or if there is a suspected allergic reaction, such as difficulty breathing or widespread rash.