Running Crab Spider
Philodromus sp.
Philodromidae, Order Araneae. Characterized by a flattened body and the second pair of legs being longer than the others.
Physical Description
Small, dorso-ventrally flattened body which allows them to squeeze into narrow crevices. The abdomen is typically teardrop-shaped or oval, ending in a slight point.
Size Estimate
Body length 3-7mm; Leg span approximately 15-25mm. This specimen appears to be an adult or sub-adult.
Coloration & Markings
Mottled brown, tan, and grey camouflage patterns. Usually features a faint cardiac mark on the anterior of the abdomen and dark speckling or banding on the legs.
Web Type
They do not build capture webs. They are active hunters that rely on speed and camouflage. They may spin 'draglines' of silk for safety and silken retreats for molting or egg-laying.
Eye Arrangement
Eight small eyes arranged in two slightly curved rows. The eyes are fairly uniform in size, which distinguishes them from the larger-eyed Jumping Spiders (Salticidae) or Wolf Spiders (Lycosidae).
Leg Characteristics
Laterigrade legs (oriented to the side like a crab). The second pair of legs (II) is notably longer than the first pair (I), which is a diagnostic feature of this family.
Venom & Safety Information
Venom Information
Possesses a mild venom used to immobilize small insects. The venom is not considered toxic to humans.
Medical Significance
Harmless. Most lack the jaw strength to pierce human skin; if a bite does occur, symptoms are usually less severe than a bee sting, involving minor localized redness or itching.
Safety Recommendations
No safety measures are necessary as they are harmless. If their presence is unwanted, they can be easily relocated using a cup and a piece of paper.
Habitat & Behavior
Habitat & Range
Found worldwide. Common in gardens, on tree bark, and frequently enter homes where they are seen on walls or ceilings.
Behavior & Temperament
Extremely fast runners and very skittish. They are ambush predators that stay still until prey is close, then strike with high-speed bursts. They are not aggressive toward humans and will usually run away at the slightest vibration.
Diet & Prey
Generalist insectivores feeding on flies, gnats, small moths, and other small wandering invertebrates.
Seasonal Activity
Visible year-round indoors, but most active outdoors during spring and summer mating seasons.
Description
The Running Crab Spider is a master of camouflage often overlooked by the casual observer. Unlike the flower-dwelling 'true' crab spiders, these lean, agile hunters prefer vertical surfaces where their mottled patterns blend into bark or neutral-colored walls.
Key Features
Second pair of legs longer than the first; flattened body; extremely rapid running movement; mottled brown/grey coloration.
Similar Species
Thomisidae (True Crab Spiders) have much larger front legs; Sparassidae (Huntsman Spiders) are significantly larger; Corinnidae (Ant-mimic spiders) have different leg proportions.
Life Cycle
Females produce flat, white silken egg sacs, often guarded until the spiderlings emerge. Life span is typically one year, with many species overwintering as juveniles.
Ecological Importance
Act as excellent natural pest control within the home and garden, preying on small flying insects and agricultural pests.
Conservation Status
Not evaluated by IUCN, but generally considered common and widespread with stable populations.
Interesting Facts
Despite being called 'crab spiders' due to their leg stance, they are more closely related to jumping spiders than to the 'true' crab spiders of the family Thomisidae.
Photography Tips
Focus on the dorsal (top-down) view to capture the leg lengths and abdominal pattern. Use a fast shutter speed as they can bolt suddenly.
Identified: 2026-05-23T23:27:02.983499