Red-backed Jumping Spider, Johnson's Jumping Spider
Phidippus johnsoni
Salticidae (Jumping Spiders), Order Araneae. Key family characteristics include large forward-facing anterior median eyes providing exceptional stereoscopic vision, robust bodies, and the ability to leap great distances.
Physical Description
A compact, robust spider with a distinctively rounded abdomen and a wide, squared cephalothorax. It features a velvety texture due to dense, fine setae (hairs). Females are typically larger and exhibit strong sexual dimorphism in coloration, though both sexes share the characteristic stout jumping spider build.
Size Estimate
Body length ranges from 7 to 13 millimeters (approximately 0.3 to 0.5 inches), with males generally on the smaller end and females on the larger end. Leg span is proportional, allowing for powerful jumps.
Coloration & Markings
Features a striking red dorsal abdomen (often divided by a faint dark line or solid bright red), jet-black legs and cephalothorax, and contrasting white markings. A prominent white band often borders the base of the abdomen where it meets the cephalothorax.
Web Type
Does not build a traditional web to catch prey. Instead, constructs a silken retreat or nest (a dense sac) under rocks, bark, or within vegetation, primarily used for molting, sleeping, and brooding eggs.
Eye Arrangement
Typical salticid arrangement with eight eyes in three rows. The front-facing anterior median eyes are exceptionally large and provide high-resolution, color vision, while the smaller secondary eyes provide a near 360-degree field of view.
Leg Characteristics
Short, muscular legs designed for explosive jumping rather than running. The anterior legs are often slightly thicker and held in a characteristic stance. Covered in fine hairs and spines for traction.
Venom & Safety Information
Venom Information
Contains neurotoxic venom tailored for subduing invertebrate prey. It is not considered medically significant to humans; its potency is very low and rarely capable of causing serious harm.
Medical Significance
Harmless to humans. A bite may cause minor, localized pain, redness, or swelling similar to a mild mosquito or ant bite. Severe systemic reactions are extremely rare. Standard first aid (soap and water, cold compress) is usually sufficient.
Safety Recommendations
No special precautions needed beyond standard observation. If found indoors, gently guide the spider into a cup using a piece of paper and release it outdoors. Do not handle roughly to prevent accidental defensive bites.
Habitat & Behavior
Habitat & Range
Found primarily in western North America, ranging from British Columbia down through California and into the Rocky Mountains. Prefers open areas, grasslands, chaparral, and the edges of forests where they hunt on low vegetation, leaf litter, and rocks.
Behavior & Temperament
Active diurnal hunter relying on stalking and calculated leaping to capture prey. Alert, curious, and fast-moving. Generally docile toward humans, though a defensive bite may occur if pressed directly against the skin.
Diet & Prey
Carnivorous predator feeding on a wide variety of small insects, including flies, ants, grasshoppers, and other spiders. Stalks prey like a cat before executing a precise, high-speed leap to subdue them with venom.
Seasonal Activity
Most active during the warm spring and summer months when prey is abundant. Overwinters as juveniles or adults sheltered inside silken retreat sacs under bark or rocks.
Description
The Red-backed Jumping Spider is one of the most charismatic and visually striking arachnids in North America. With its velvety red back, jet-black body, and large, intelligent-looking eyes, it captures the interest of nature enthusiasts everywhere. As an active hunter roaming through grass and low shrubs, it relies on incredible eyesight and athletic leaps rather than webs to secure its meals.
Key Features
Brilliant red dorsal abdomen contrasting with solid black legs and cephalothorax, large forward-facing eyes, and characteristic bounding movement.
Similar Species
Other red-backed jumping spiders such as Phidippus apacheanus, which tends to be found further east and in warmer, more arid southern regions. Distinguish by subtle differences in geographical range, white basal band markings, and precise stripe patterns.
Life Cycle
Females construct a silken retreat to deposit eggs, guarding them until they hatch. Spiderlings go through multiple molts as they grow. Lifespan typically ranges from one to two years under favorable conditions.
Ecological Importance
Acts as an effective natural pest controller in gardens, grasslands, and agricultural areas by keeping populations of small insect pests in check.
Conservation Status
Not evaluated by the IUCN, but populations are generally stable and widespread throughout their native western North American range.
Interesting Facts
Jumping spiders can leap up to 50 times their own body length using sudden hydraulic pressure changes in their legs. They are also known to perceive color in the ultraviolet spectrum.
Photography Tips
Use a macro lens in bright natural daylight to capture the iridescent sheen on the chelicerae and the intricate detail of the large, expressive eyes. Shoot from a low angle at eye level for the most engaging portrait.
User Notes
Grass
Identified: 2026-10-01T19:10:38.952976