Black-footed Spider, Yellow Sac Spider, Northern Yellow Sac Spider
Cheiracanthium mildei
Cheiracanthiidae (Long-legged Sac Spiders), Order Araneae
Physical Description
A medium-sized spider with a slightly elongated cephalothorax and an oval-shaped abdomen. The body is relatively smooth with very fine hairs. It lacks the bulky appearance of a wolf spider or the flattened shape of a crab spider.
Size Estimate
Body length 5-10mm (0.2-0.4 inches) with a leg span reaching up to 25mm (1 inch). This appears to be an adult female.
Coloration & Markings
Characteristically pale yellow, tan, or light greenish-yellow. It often has a slightly darker dorsal stripe on the abdomen. The most diagnostic feature is the dark brown or black coloration at the tips of the 'feet' (tarsi).
Web Type
Does not build a capture web for hunting. Instead, it constructs a small, white, silk retreat or 'sac' in corners (where walls meet ceilings) for resting during the day and for laying eggs.
Eye Arrangement
Eight eyes in two horizontal rows of four. The eyes are relatively small and equal in size, distributed across the front of the cephalothorax.
Leg Characteristics
The legs are long, slender, and pale. The first pair of legs is significantly longer than the others. They lack conspicuous banding but have the characteristic dark tips.
Venom & Safety Information
Venom Information
Cytotoxic venom. Historically incorrectly blamed for necrotic lesions similar to brown recluse bites, but modern research suggests the venom typically causes localized swelling and pain.
Medical Significance
Low to Moderate. Bites are painful (similar to a bee sting) with localized redness and itching. They are not considered medically dangerous to healthy humans and do not cause systemic necrosis.
Safety Recommendations
Relocate using a jar and paper if found. Shake out clothing or shoes left on the floor. If bitten, wash with soap and water and apply a cold compress.
Habitat & Behavior
Habitat & Range
Native to Europe and introduced to North America, where it is now very common in homes, gardens, and agricultural fields. They are frequently found indoors on walls and ceilings.
Behavior & Temperament
Active nocturnal hunters. They roam at night to search for prey of their own. They are generally shy and will retreat if disturbed, but may bite if trapped against skin (e.g., inside clothing or bedding).
Diet & Prey
Generalist predators feeding on small insects, other spiders, and insect eggs. They are known to even consume plant nectar for energy when prey is scarce.
Seasonal Activity
Active year-round indoors, but most frequent in late summer and autumn when they enter homes or reach maturity.
Description
A slender, pale yellow spider commonly found scurrying across ceilings at night. Identified by its translucent appearance and dark tarsal claws, it is a frequent guest in human dwellings where it provides natural pest control.
Key Features
Pale yellow/greenish translucent body, dark 'feet', long front legs, and the presence of small silk sleeping sacs in wall-ceiling corners.
Similar Species
Cheiracanthium inclusum (virtually identical without microscopic study), Anyphaenidae (Ghost Spiders), and young Hibana species.
Life Cycle
Females produce several egg sacs in summer and autumn, often guarding them inside their silk retreats. Spiderlings emerge and may stay near the mother briefly before dispersing. Lifespan is approximately one year.
Ecological Importance
Significant residential and agricultural pest control agents, preying on flies, moths, and agricultural pests like leafhoppers.
Conservation Status
Not evaluated by IUCN, but widespread, abundant, and often considered an invasive or synanthropic species.
Interesting Facts
They are known 'active explorers' and are frequently found inside vehicles or moved across the country through nursery stock and produce shipping.
Photography Tips
Focus on the front legs to show length and the dark tips of the tarsi. Lateral or top-down views are best for showing the abdominal stripe.
Identified: 2026-06-17T03:02:57.562279