Black-footed Spider, Yellow Sac Spider, Long-legged Sac Spider
Cheiracanthium mildei
Cheiracanthiidae (Sac Spiders), Order Araneae. Characterized by building silk retreats (sacs) rather than capture webs.
Physical Description
Elongated, slightly flattened cephalothorax with an oval abdomen. The body has a somewhat translucent or pearlescent quality. It lacks prominent hairs, appearing relatively smooth or finely velvety. In this specimen, the prominent pedipalps (the small appendages near the head) suggest it is a mature male.
Size Estimate
The body length is approximately 5 to 10 mm (0.2 to 0.4 inches) with a leg span reaching about 25 mm (1 inch). This appears to be an adult male based on the enlarged pedipalps.
Coloration & Markings
Pale yellow, tan, or light greenish-yellow overall. The abdomen often has a faint darker dorsal stripe (the 'cardiac mark'). A distinguishing feature from which it gets its common name is the dark, almost black coloration at the tips of the 'feet' (tarsi).
Web Type
This spider does not build a traditional web to catch prey. Instead, it constructs a small, white, silk 'sac' or tube in corners of ceilings, walls, or folded leaves to rest in during the day.
Eye Arrangement
Eight small eyes arranged in two horizontal rows of four. The eyes are relatively uniform in size compared to hunting spiders like jumpers or wolf spiders.
Leg Characteristics
Legs are long and slender. The first pair of legs is significantly longer than the others. They possess 'claw tufts' or scopulae at the tips, allowing them to easily climb smooth vertical surfaces and walk across ceilings.
Venom & Safety Information
Venom Information
Contains a mild cytotoxin. Historically, they were incorrectly accused of causing necrotic skin lesions similar to brown recluses, but modern research has largely debunked this significance.
Medical Significance
Low danger level. Bites are typically comparable to a bee sting, causing localized pain, swelling, and redness that usually subsides within 24–48 hours. No medical treatment is usually required unless an allergic reaction occurs.
Safety Recommendations
To avoid bites, shake out clothing or shoes left on the floor. If a spider is on the ceiling, it can be safely caught in a jar and relocated outside. They are not aggressive and do not seek out human contact.
Habitat & Behavior
Habitat & Range
Found globally; common in Europe, North Africa, and North America. In homes, they are frequently found where the wall meets the ceiling or behind furniture. Outdoors, they reside in foliage or under bark.
Behavior & Temperament
An active nocturnal hunter that wanders in search of prey at night. They are agile and fast. While typically shy and prone to fleeing, they can be defensive if trapped against the skin (e.g., inside clothing or bedding).
Diet & Prey
Generalist predators feeding on various small insects, such as fruit flies, gnats, and other spiders. They use their speed to overpower prey rather than silk entanglement.
Seasonal Activity
Active year-round indoors but most frequently noticed in late summer and autumn as they mature and wander more extensively to find mates.
Description
A ubiquitous indoor resident, the Yellow Sac Spider is often seen at night traversing walls or ceilings. Its pale, translucent body and long front legs make it a distinct figure in the home. Despite their reputation, they are beneficial hunters of indoor pests and are generally harmless to humans.
Key Features
Pale yellow/translucent coloration, dark 'feet', first pair of legs longer than the rest, and the presence of small silk retreats in room corners.
Similar Species
Often confused with the Brown Recluse (Loxosceles reclusa), but lacks the 'violin' marking on the cephalothorax and has different eye arrangements. Also similar to Ghost Spiders (Anyphaenidae).
Life Cycle
Females lay eggs inside a reinforced silk sac and remain with them until they hatch. Spiderlings may stay near the mother for a short time before dispersing. Total lifespan is generally around one year.
Ecological Importance
Act as a natural pest control agent in residential and agricultural environments, significantly reducing populations of flies and small lepidopterans.
Conservation Status
Not evaluated by the IUCN; considered very stable and common as a synanthropic species (thriving in human-disturbed habitats).
Interesting Facts
They are known for their exceptional climbing ability, enabled by dense brushes of hair on their feet that use van der Waals forces to stick to glass and smooth drywall.
Photography Tips
Since they are pale, avoid using a direct flash which will wash out their features. Side-lighting helps reveal the texture of the abdomen and the cardiac mark. Try to focus on the front of the cephalothorax to capture the eye pattern.
User Notes
Found on ceiling in house
Identified: 2026-06-27T17:24:58.444952