Woodlouse spider, Pillbug hunter, Sowbug killer
Dysdera crocata
Dysderidae (Woodlouse Spiders), Order Araneae. Key family characteristics include having six eyes arranged in a compact, oval cluster and extremely large, prominent chelicerae (jaws) adapted for piercing hard-shelled prey.
Physical Description
The woodlouse spider features a distinctive, glossy dark reddish-brown to mahogany cephalothorax and legs, paired with a smooth, elongated, cylindrical, dull beige, yellowish, or pale greyish-pink abdomen. Its most striking anatomical feature is a pair of massive, forward-projecting chelicerae that are heavily modified to grasp armored prey.
Size Estimate
Body length typically ranges from 11 to 15 millimeters for females, and 9 to 10 millimeters for males. The leg span is roughly equivalent to or slightly greater than the body length, giving it a compact yet formidable appearance.
Coloration & Markings
The anterior portion, including the cephalothorax, legs, and chelicerae, exhibits a uniform shiny deep red or brownish-orange. The large abdomen contrasts sharply as a pale, translucent pinkish-gray or beige without distinct patterns or markings.
Web Type
Dysdera crocata does not spin webs to catch prey. Instead, it constructs a silken retreat or shelter, often under logs, stones, or bark, where it rests during the daytime.
Eye Arrangement
Equipped with six eyes positioned closely together in a tight, compact oval group on the front-top of the cephalothorax, which is a diagnostic trait of the family Dysderidae.
Leg Characteristics
The legs are relatively short, stout, and robust, colored uniformly to match the cephalothorax. They lack complex banding patterns and are equipped with strong spines used to secure struggling, hard-shelled prey.
Venom & Safety Information
Venom Information
Possesses a specialized venom designed to paralyze arthropods quickly. The venom has very low toxicity to humans and is generally considered medically insignificant.
Medical Significance
Not medically significant. A bite may cause minor, localized pain, slight swelling, and a small puncture mark, but symptoms typically resolve quickly without medical intervention. Severe allergic reactions are extremely rare.
Safety Recommendations
Avoid handling them with bare hands to prevent defensive bites. If found indoors, they can be safely relocated outside using a container and a piece of paper. No professional pest control is necessary.
Habitat & Behavior
Habitat & Range
Widely distributed globally, particularly in temperate regions of Europe, North America, Australia, and New Zealand. They favor damp terrestrial microhabitats such as under rocks, logs, leaf litter, and in gardens, often found in close proximity to their primary prey.
Behavior & Temperament
Nocturnal and roaming hunters that actively forage outside their silken daytime retreats. They are generally non-aggressive toward humans, though they will bite in self-defense if handled or trapped directly against the skin.
Diet & Prey
Specialized almost exclusively in feeding on terrestrial isopods, commonly known as woodlice, pillbugs, or sowbugs. Their exceptionally long fangs are uniquely adapted to pierce the hard, calcified exoskeleton of these crustaceans.
Seasonal Activity
Active primarily from spring through autumn. During the coldest winter months, they seek shelter deep beneath the frost line in underground burrows or under heavy stones.
Description
The woodlouse spider is an easily recognizable and fascinating nocturnal hunter found in gardens and damp outdoor areas. With its glossy reddish-brown front half, oversized forward-pointing fangs, and pale greyish abdomen, it looks entirely built for a specific purpose: tracking down and consuming armored woodlice. Though its appearance can occasionally startle homeowners, it is a harmless and beneficial garden resident that preys on creatures few other spiders can manage.
Key Features
Glossy reddish-brown cephalothorax and legs, pale pinkish-beige abdomen, massive protruding chelicerae (jaws), six eyes in a compact cluster, and lack of distinct abdominal markings.
Similar Species
Can sometimes be confused with broad-faced sac spiders (Trachelas species) or female black widows due to coloration, but is easily distinguished by its massive forward-facing jaws, pale abdomen, and lack of an hourglass marking.
Life Cycle
Females construct silken egg sacs in secluded retreats under objects on the ground, containing dozens of eggs. Spiderlings hatch and remain with the mother briefly before dispersing. They mature over the course of one to two years, undergoing multiple molts.
Ecological Importance
Serves as an effective natural controller of woodlouse and pillbug populations in gardens and yards, helping to regulate detritivore numbers within the local food web.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and frequently benefit from human agricultural and suburban expansion which introduces abundant woodlouse populations.
Interesting Facts
The woodlouse spider's fangs are so long that they are actually oriented parallel to each other and strike forward like ice tongs rather than pinching inward, an evolutionary adaptation required to pierce the rounded shells of pillbugs.
Photography Tips
Photograph from a side or slightly elevated angle to clearly capture the distinctive contrast between the reddish front section and pale abdomen, as well as the prominent jaws. Use natural diffused lighting and a macro lens while keeping a safe distance.
User Notes
On back patio
Identified: 2026-10-08T23:13:50.093764