Oblong Running Spider, Slender Crab Spider
Tibellus oblongus
Philodromidae (Running Crab Spiders), Order Araneae
Physical Description
Characterized by a highly elongated, slender, and flattened body. The cephalothorax is longer than it is wide, and the abdomen is cigar-shaped or 'oblong', tapering toward the rear. The body is relatively smooth with fine, appressed hairs.
Size Estimate
Body length 7–11 mm (females), 5–8 mm (males). Leg span typically reaches 25–40 mm. This specimen appears to be an adult female.
Coloration & Markings
Pale straw-yellow to light tan base coloration. It features a distinctive dark brown or grey longitudinal stripe running down the center of the cephalothorax and abdomen, often flanked by two lighter parallel stripes. Small black dots (puncta) may be visible on the abdomen.
Web Type
This is a hunting spider that does not build a web for prey capture. It uses silk only for egg sacs and draglines. It is often found resting flat against blades of grass.
Eye Arrangement
Eight eyes arranged in two rows. The posterior row is significantly more recurved than the anterior row, and the eyes are spread widely across the front of the cephalothorax to provide a wide field of view.
Leg Characteristics
Long, slender legs held in a flattened lateral (crab-like) posture. The second pair of legs is usually slightly longer than the others. Legs are typically the same color as the body with very fine dark spotting or spines.
Venom & Safety Information
Venom Information
Possesses mild venom used to paralyze small insects. The venom is not considered toxic to humans or large pets.
Medical Significance
Negligible. Harmless to humans. Bites are extremely rare due to the spider's timid nature and weak fangs which struggle to pierce human skin.
Safety Recommendations
No special precautions needed. If found indoors, they can be safely relocated outside using a cup and paper. They pose no threat to structures or inhabitants.
Habitat & Behavior
Habitat & Range
Common throughout the Holarctic region (North America, Europe, and Northern Asia). Preferred habitats include tall grasslands, meadows, dunes, and marshes where they can camouflage against dried vegetation.
Behavior & Temperament
Diurnal active hunter. It relies on extreme camouflage, stretching its legs forward and backward to align with grass blades. It is shy, non-aggressive, and will quickly run or drop to the ground if disturbed.
Diet & Prey
Generalist insectivore. It feeds on small flies, leafhoppers, and other grass-dwelling insects, utilizing speed and ambush rather than silk to subdue prey.
Seasonal Activity
Most active from late spring through autumn. Peak sightings occur in mid-summer during the mating season.
Description
A master of disguise in the meadow, the Oblong Running Spider is a specialized hunter evolved for life among vertical stalks. Its streamlined shape and neutral tones allow it to vanish against sun-bleached grass.
Key Features
Elongated 'cigar' abdomen, central longitudinal stripe, and the habit of resting with legs stretched out linearly (two pairs forward, two pairs back).
Similar Species
Tibellus maritimus (very similar, requiring microscopic examination of genitalia to distinguish) and Thanatus species (which are generally shorter and more robust).
Life Cycle
Females produce flat, white silken egg sacs attached to vegetation, which they often guard until the spiderlings emerge. They typically live for one year, overwintering as sub-adults.
Ecological Importance
Serves as an important biological control agent for agricultural and grassland pests like aphids and plantbugs.
Conservation Status
Not evaluated by the IUCN, but generally considered common and widespread with stable populations.
Interesting Facts
Unlike typical crab spiders (Thomisidae), Philodromids like Tibellus are much faster runners. Their body shape is a perfect example of protective resemblance, mimicking the shape and color of dry grass.
Photography Tips
Focus on the dorsal stripe and the eye arrangement. Side-profile shots are useful to show the flattened body shape. Use natural light to highlight the subtle tan textures.
Identified: 2026-07-19T20:56:25.885097