Yellow Sac Spider, Long-legged Sac Spider, Agrarian Sac Spider
Cheiracanthium mildei
Cheiracanthiidae (Sac Spiders), Order Araneae. Historically placed in Miturgidae or Clubionidae.
Physical Description
A medium-sized spider with a robust cephalothorax and an oval-shaped abdomen. The body is relatively smooth with very fine, translucent hairs. The chelicerae (mouthparts) are noticeable and often appear darker than the rest of the head.
Size Estimate
Body length 5-10 mm; total leg span 20-30 mm. This specimen looks like an adult female based on body proportions.
Coloration & Markings
Translucent pale yellow to light lime green. A faint longitudinal 'heart mark' is often visible on the anterior of the abdomen. No distinct stripes or spots are present.
Web Type
Does not build hunting webs. Instead, it constructs a typical 'sac' or silk retreat for resting during the day, usually in corners, wall-ceiling junctions, or folded leaves.
Eye Arrangement
Two horizontal rows of four eyes each (8 total). The eyes are relatively equal in size and lack the prominent arrangement of jumping or wolf spiders.
Leg Characteristics
The first pair of legs is significantly longer than the others. They are slender, translucent, and lack heavy spines or distinct banding.
Venom & Safety Information
Venom Information
Contains a mild cytotoxin. Historically and incorrectly associated with necrotic lesions similar to recluse spiders, but recent clinical studies have debunked this.
Medical Significance
Low concern. Bites are usually painful (similar to a bee sting) with localized redness and swelling. Most symptoms resolve within 72 hours without medical intervention.
Safety Recommendations
Relocate using a jar and card. To prevent indoor encounters, seal gaps in windows and clear vegetation from the home's foundation.
Habitat & Behavior
Habitat & Range
Commonly found throughout North America and Europe. They are highly synanthropic, frequently inhabiting human dwellings, gardens, and agricultural fields.
Behavior & Temperament
Active nocturnal hunters. They are fast-moving and prone to wandering indoors at night. While not aggressive, they may bite if trapped against skin or disturbed in their silk sacs.
Diet & Prey
Generalist predator feeding on small insects, other spiders, and insect eggs. They are active hunters that do not use webs to snare prey.
Seasonal Activity
Active year-round indoors, but most visible in late summer and early autumn when males wander in search of mates.
Description
An elegant, pale yellow wanderer often spotted on walls or ceilings at night. Its translucent appearance and long front legs make it a distinctive member of the indoor ecosystem.
Key Features
Pale yellow/green body, no markings, long front legs, construction of vertical silk resting sacs in corners.
Similar Species
Loxosceles reclusa (Brown Recluse), which has a darker violin shape and different eye pattern; and Clubiona species, which are typically browner.
Life Cycle
Females produce silk egg sacs in protected areas and remain with them until the spiderlings emerge. They typically live for about one year, maturing in late summer.
Ecological Importance
Excellent biological pest control, particularly for agricultural pests like leafhoppers and various moth larvae in gardens.
Conservation Status
Not evaluated by IUCN; widely considered abundant and secure due to adaptability to human environments.
Interesting Facts
A significant portion of their diet can include plant nectar, an unusual trait for spiders. They are also known to be attracted to the smell of certain chemicals used in gasoline.
Photography Tips
Focus on the front of the cephalothorax to capture the eye arrangement and dark fangs. Backlighting highlighting the translucent legs works well.
Identified: 2026-06-22T04:10:16.433250