Yellow Sac Spider, Long-legged Sac Spider
Cheiracanthium inclusum (or Cheiracanthium mildei)
Eutichuridae (formerly Miturgidae), Order Araneae. Characterized by running spiders that construct silken retreat sacs.
Physical Description
Elongated body with a slightly oval abdomen and a distinct, pear-shaped cephalothorax. The surface is smooth with fine hairs, lacking striking spines or patterns, presenting a relatively uniform silhouette.
Size Estimate
Body length typically ranges from 5 to 10 millimeters, with a leg span of roughly 25 to 30 millimeters. The specimen appears to be an adult or sub-adult.
Coloration & Markings
Pale yellow, yellowish-green, or beige overall. Often features a subtle, darker longitudinal stripe running down the center of the abdomen. The jaws may have a slightly darker brownish tint.
Web Type
Does not build a traditional prey-catching web. Instead, it spins a small, flattened silken tube or sac used as a daytime retreat, typically tucked into upper wall corners, ceilings, or shower stalls.
Eye Arrangement
Eight relatively uniform eyes arranged in two slightly recurved rows of four. The eyes are not dramatically disparate in size, which is typical for the family.
Leg Characteristics
Long, slender legs with the first pair noticeably longer than the others. They lack prominent banding but feature claw tufts at the tips, often held in a characteristic sprawling posture.
Venom & Safety Information
Venom Information
Cytotoxic venom used to subdue invertebrate prey. Mildly potent to humans, causing localized pain, redness, and occasional minor swelling.
Medical Significance
Minimally dangerous to humans. Bites are rare and usually occur when the spider is accidentally trapped against the body. Symptoms typically resemble a mild bee sting and resolve within a few days.
Safety Recommendations
Shake out clothing or towels left on the floor. If found in a shower, gently guide it into a cup using a piece of paper and release it outdoors.
Habitat & Behavior
Habitat & Range
Found worldwide, heavily adapted to human structures including homes, garages, and damp areas like bathrooms, as well as outdoor foliage and gardens.
Behavior & Temperament
Nocturnal active hunter that leaves its silken retreat at night to forage. Generally non-aggressive unless trapped or pressed against human skin.
Diet & Prey
Carnivorous, feeding on a wide variety of household and garden pests, including flies, mosquitoes, moths, and other small spiders.
Seasonal Activity
Most active during late spring through autumn, seeking shelter indoors as temperatures drop in the late fall.
Description
The yellow sac spider is a frequent indoor companion, often discovered roaming bathtubs or clinging to upper corners. Recognized by its pale yellowish-green hue and swift movements, it plays a beneficial role in controlling household insects.
Key Features
Pale yellow-green coloration, cylindrical abdomen with an indistinct darker dorsal stripe, noticeably elongated first pair of legs, and the habit of resting in a small silken sac.
Similar Species
Can be confused with other wandering household spiders such as ghost spiders (Anyphaenidae) or small grass spiders (Agelenidae), but is distinguished by its uniform pale color and lack of distinct abdominal patterns.
Life Cycle
Females construct silken egg sacs in secluded areas during late spring or summer, depositing several dozen eggs. Spiderlings hatch and overwinter inside protective retreats, maturing by the following year.
Ecological Importance
Serves as an effective natural pest controller in both agricultural fields and residential structures, helping keep populations of nuisance insects in check.
Conservation Status
Not evaluated by the IUCN, but populations are abundant, widespread, and thriving globally.
Interesting Facts
Yellow sac spiders are notorious wanderers and are frequently responsible for mysterious indoor spider bites due to their tendency to construct retreats in clothing or bedding.
Photography Tips
Use macro lenses with good side-lighting to highlight the subtle dorsal stripe and eye arrangement. Maintain a safe distance and photograph against a neutral background for clarity.
User Notes
Found in my shower
Identified: 2026-09-22T09:42:55.652111