Mouse Spider, European Mouse Spider
Scotophaeus blackwalli
Family Gnaphosidae (Ground Spiders), Order Araneae
Physical Description
The spider has a flat, torpedo-shaped body characteristic of ground spiders. The abdomen is covered in fine, velvety grey hairs that resemble mouse fur. The cephalothorax is reddish-brown and glossy, contrasting with the duller abdomen.
Size Estimate
Body length 9–12 mm (females), 7–9 mm (males). Leg span is moderate, typically ranging from 15–25 mm.
Coloration & Markings
The abdomen is a uniform mouse-grey or silvery-grey. The cephalothorax and legs are dark reddish-brown to almost black. There are no striking chevrons or stripes, but the spinnerets are prominent and barrel-shaped.
Web Type
The Mouse Spider does not build a web for hunting. Instead, it creates a small, silk-lined retreat in a crevice where it rests during the day.
Eye Arrangement
Eight eyes in two nearly straight rows of four. The posterior median eyes are often oval or irregular in shape and possess a silvery luster, which is diagnostic for the family Gnaphosidae.
Leg Characteristics
The legs are robust and strong, designed for sprinting. They are dark brown, covered in fine hairs, and lack prominent banding.
Venom & Safety Information
Venom Information
The venom is primarily used to immobilize small invertebrates. It is not considered toxic to humans, though some reports suggest minor local reactions due to individual sensitivity.
Medical Significance
Low medical significance. The bite is comparable to a bee sting, causing localized pain, redness, and minor swelling. It is not dangerous unless the person has a rare allergic reaction.
Safety Recommendations
If found indoors, they can be safely relocated using a jar and a piece of paper. Wear gloves if handling woodpiles where they may hide to avoid defensive nips.
Habitat & Behavior
Habitat & Range
Originally from Europe, it is now widely established in North America and parts of the Southern Hemisphere. It is synanthropic, meaning it is commonly found inside houses, under bark, or in gardens.
Behavior & Temperament
A nocturnal wandering hunter. It is extremely fast and agile, capable of subduing prey larger than itself. They are generally timid and will sprint for cover if disturbed but may bite if pressed against skin.
Diet & Prey
Generalist predator eating insects and other spiders. They are known to scavenge dead insects and can overpower other house spiders, including cellar spiders and small lace-web spiders.
Seasonal Activity
Active year-round indoors, but most visible in late summer and autumn when males wander in search of mates.
Description
The Mouse Spider is a stealthy, nocturnal visitor often seen darting across walls or floors at night. Named for its velvety grey appearance and mouse-like speed, it is a beneficial predator that keeps indoor pest populations in check.
Key Features
Velvety grey abdomen, reddish-brown cephalothorax, barrel-shaped spinnerets, and extreme speed.
Similar Species
Often confused with Missulena species (Australian Mouse Spiders), which are much larger and medically significant. Also similar to other ground spiders like Drassodes, which are lighter in color.
Life Cycle
Females produce a white, papery egg sac that they guard in their silk retreat. Spiderlings emerge and disperse. They typically live for 1 to 2 years.
Ecological Importance
Provides natural pest control in homes and gardens by preying on silverfish, flies, and other household insects.
Conservation Status
Not evaluated by IUCN, but widespread and common; populations are stable.
Interesting Facts
Despite their small size, they are formidable hunters and have been recorded successfully attacking spiders much larger than themselves in a domestic setting.
Photography Tips
Focus on the spinnerets at the rear of the abdomen and the texture of the abdominal hair. Use a fast shutter speed to catch them between bursts of speed.
Identified: 2026-06-15T12:54:12.234841