Red-backed Jumping Spider, Johnson's Jumping Spider
Phidippus johnsoni
Family Salticidae (Jumping Spiders), Order Araneae
Physical Description
A robust, highly hirsute jumping spider. The abdomen features a broad dorsal surface covered in dense orange-red scales, bordered or divided centralizingly by a dark longitudinal stripe/folium. The cephalothorax, chelicerae, and legs are thick, covered in dark blackish setae interspersed with lighter hairs.
Size Estimate
Body length is typically 9 to 14 mm for females and 8 to 11 mm for males, with a total leg span reaching around 15 to 20 mm. This specimen appears to be an adult female based on the prominent central abdominal stripe and thick body shape.
Coloration & Markings
Bright bright rust-red to vivid orange dorsal surface on the abdomen, with a characteristic central black longitudinal stripe or patch. The carapace and legs are jet black with light greyish or white hairs creating a frosted appearance along the leg segments.
Web Type
Does not spin capture webs for hunting. Constructs small, tube-like silk retreat nests under rocks, bark, woodpiles, or crevices for resting, molting, overwintering, and laying eggs.
Eye Arrangement
Typical Salticidae configuration with eight eyes: two exceptionally large Anterior Median Eyes (AME) positioned forward on the flat face providing high-resolution stereoscopic vision, flanked by smaller Anterior Lateral Eyes (ALE) and Posterior Lateral Eyes (PLE) situated further back on the cephalothorax.
Leg Characteristics
Thick, sturdy, and relatively short legs built for jumping rather than running. Densely covered in black and grey spiky setae and hairs, ending in specialized claw tufts (scopulae) that allow them to walk easily on glass and vertical surfaces.
Venom & Safety Information
Venom Information
Uses mild, fast-acting neurotoxic venom optimized to immobilize small insect prey quickly. Harmless and non-lethal to humans.
Medical Significance
Not medically significant. Bites are rare and only occur if forcefully crushed or pinched. A bite causes localized pain, mild swelling, and redness similar to a bee sting, resolving in a few hours without treatment.
Safety Recommendations
No extermination or chemical control required. If found indoors, safely capture it using the cup-and-paper method and relocate it to a garden, tree trunk, or outdoor wall.
Habitat & Behavior
Habitat & Range
Native to western North America, ranging from coastal regions to inland deserts and mountain areas, common throughout the Pacific Coast states, Great Basin, and Southwestern United States. Prefers dry, open habitats, backyard gardens, rocky outcrops, and wooden structures.
Behavior & Temperament
Active diurnal hunter utilizing visual cues to stalk prey. Curiously observes surroundings and shows sophisticated spatial awareness. Highly agile, able to jump many times its body length. Docile toward humans and retreats if threatened.
Diet & Prey
Pounce hunter feeding on flies, moths, grasshoppers, beetles, caterpillars, and occasionally other spiders. Capable of overpowering prey significantly larger than itself.
Seasonal Activity
Most active from spring through early autumn. Adults are frequently spotted basking on sunny surfaces or hunting on plants in early summer.
Description
Phidippus johnsoni is one of the largest and most striking jumping spiders found in western North America. Renowned for its bright orange-red abdomen and inquisitive nature, this charismatic arachnid relies on its incredible vision and explosive jumping power rather than webs to catch prey. Highly beneficial in gardens, it actively hunts common agricultural pests while demonstrating remarkable cognitive capabilities.
Key Features
Vivid orange-red abdominal dorsum with a central black longitudinal stripe or spot, black fuzzy legs with grey/white banding, robust setose body, and two massive forward-facing median eyes.
Similar Species
Phidippus clarus (similar red abdominal pattern but typically found in central/eastern regions), Phidippus audax (usually black with white spots, though juveniles can show orange), and Castianeira species (ant-mimicking spiders lacking jumping eye arrangement).
Life Cycle
Females construct silk egg sacs inside silken retreat nests during late spring and summer, guarding eggs until hatching. Spiderlings disperse via ballooning or walking. Total lifespan is generally 1 to 2 years.
Ecological Importance
Serves as an essential natural pest controller in gardens, croplands, and natural ecosystems, regulating populations of destructive insects like aphids, flies, bugs, and caterpillars.
Conservation Status
Not evaluated by the IUCN. Abundant throughout its natural range with stable populations and no major conservation threats.
Interesting Facts
Jumping spiders have the visual acuity among the best of all invertebrates, allowing them to perceive color, depth, and fine details up to several feet away. Males perform elaborate visual courtship displays including leg waves and abdomen vibratory taps.
Photography Tips
Focus sharply on the face to capture the iconic large eyes and iridescent chelicerae. Use macro lenses with ring flashes, taking advantage of the spider's curious nature as it often turns directly toward the camera lens.
Identified: 2026-07-25T15:47:42.872043