Woodlouse Spider, Woodlouse Hunter, Sowbug Killer
Dysdera crocata
Dysderidae (Woodlouse Spider Family), Order Araneae. Key family characteristics include six eyes arranged in a tight, compact cluster on the front of the head and enlarged, forward-projecting chelicerae adapted for piercing hard-shelled prey.
Physical Description
The woodlouse spider features a distinctive elongated, glossy dark red-brown to orange cephalothorax and a pale beige, greyish, or yellowish-brown oval abdomen. Its most striking anatomical feature is its oversized, menacing chelicerae (jaws) which project forward rather than pointing downward.
Size Estimate
Body length typically ranges from 11 to 15 mm for females and 9 to 10 mm for males, with a leg span of approximately 20 to 25 mm. The specimen in the image appears to be a typical adult.
Coloration & Markings
Characterized by a vibrant, shiny reddish-brown to bright orange-red cephalothorax and legs, contrasting sharply with a dull, plain, soft-looking greyish-beige or yellowish-white abdomen lacking distinct patterns or markings.
Web Type
Dysdera crocata does not spin a web to capture prey. Instead, it constructs a silken retreat or daytime shelter, usually a small sac or cell under rocks, logs, bark, or inside crevices where it rests during daylight hours.
Eye Arrangement
Features six eyes arranged in a tight, compact, horseshoe-shaped oval cluster at the front center of the cephalothorax, which is characteristic of the Dysderidae family.
Leg Characteristics
Legs are relatively short, robust, and colored to match the reddish-brown cephalothorax. They are adapted for crawling swiftly through leaf litter and crevices rather than running on open ground or climbing smooth vertical surfaces.
Venom & Safety Information
Venom Information
Possesses mild venom used to subdue invertebrate prey. It is not considered dangerous or lethal to humans, though its large fangs can deliver a surprisingly painful mechanical pinch.
Medical Significance
Not medically significant. A bite may cause minor local pain, slight swelling, and redness that typically resolves within a day without medical intervention. There is no risk of systemic toxicity.
Safety Recommendations
Wear gloves when gardening under rocks or decaying wood. If found inside, gently capture it under a glass and release it outdoors. Bites are rare and easily avoided by not handling the spider directly.
Habitat & Behavior
Habitat & Range
Native to Europe, but now widely introduced across North America, parts of South America, Australia, and New Zealand. Found primarily in damp, dark terrestrial microhabitats such as under stones, logs, leaf litter, and frequently wanders into human homes, particularly basements and bathrooms.
Behavior & Temperament
A nocturnal, active hunter that spends daylight hours hiding in its silken retreat. It has a defensive temperament and will bite if handled or accidentally compressed, though it is generally non-aggressive toward humans.
Diet & Prey
Specialized feeder that preys almost exclusively on woodlice (sowbugs and pillbugs). Its enormous, specialized chelicerae are uniquely adapted to pierce the hard exoskeleton of crustaceans that most other spiders cannot penetrate.
Seasonal Activity
Most active during spring and autumn when humidity is high and prey is abundant. They overwinter by sheltering deep under logs, rocks, or inside foundations.
Description
The woodlouse spider is a fascinating specialist easily recognized by its glossy reddish-brown armor and formidable, oversized jaws. Perfectly adapted for hunting terrestrial isopods in damp garden habitats, this nocturnal wanderer occasionally finds its way indoors, often startling homeowners despite its harmless nature.
Key Features
Shiny dark red-brown or orange cephalothorax, pale oval abdomen, six eyes in a tight cluster, and extraordinarily long, forward-pointing chelicerae designed for hunting woodlice.
Similar Species
Can sometimes be confused with broad-faced sac spiders (Trachelas tranquillus) or wood spiders, but can be instantly distinguished by its specialized red jaws and six-eye arrangement rather than eight eyes.
Life Cycle
Females construct a silken egg sac in their retreat where they lay dozens of eggs, often guarding them. Spiderlings hatch and stay close initially before dispersing. Lifespan typically ranges from 1.5 to 2 years.
Ecological Importance
Acts as an effective natural controller of woodlouse populations in gardens and forest floors, helping regulate decomposer populations and maintaining ecological balance.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and thriving globally, frequently expanding their range via human commerce.
Interesting Facts
Despite having large, terrifying-looking fangs capable of piercing human skin, woodlouse spiders are completely harmless to humans and pets, dedicating their hunting prowess entirely to getting rid of garden pests like roly-polies.
Photography Tips
Use macro photography with natural, diffused side lighting to highlight the glossy texture of the cephalothorax and the intricate structure of the fangs. Keep a safe distance or use a macro lens to avoid startling the spider.
Identified: 2026-10-09T17:03:36.738758