The woodlouse spider (Dysdera crocata) is a commonly encountered arachnid often recognized by its distinctive appearance. Despite its somewhat intimidating look, characterized by unusually large fangs, the woodlouse spider is generally not considered dangerous to humans.
Recognizing the Woodlouse Spider
Woodlouse spiders have several key physical characteristics. Adult females of Dysdera crocata can reach a body length of up to 15 millimeters, while males are slightly smaller, around 10 millimeters. Its cephalothorax and legs are typically a tawny orange to dark-red, contrasting with its shiny, pale beige, yellow-brown, or grayish-white abdomen.
A striking feature is its disproportionately large, forward-pointing chelicerae, or fangs. These fangs are adapted for piercing the tough exoskeletons of its primary prey, woodlice. Unlike most spiders that have eight eyes, the woodlouse spider has six eyes, typically arranged in a tight cluster at the front of its cephalothorax. This species does not spin webs for catching prey; instead, it is a nocturnal hunter that actively searches for food. These spiders are often found in dark, damp environments, such as under logs, rocks, leaf litter, and in basements or crawl spaces indoors.
Understanding Their Bite
The primary concern for many encountering a woodlouse spider is its bite, given its prominent fangs. While Dysdera crocata can bite if provoked or accidentally pressed against human skin, their venom is not considered medically significant to humans. The bite is generally described as causing mild to moderate pain, often compared to a bee sting, primarily due to the mechanical puncture from its large fangs rather than the venom itself.
Following a bite, common symptoms include localized pain, redness, and mild swelling at the bite site. Some individuals might also experience slight itching or irritation, similar to a mosquito bite. These local reactions are typically short-lived, with pain often subsiding within an hour. Systemic reactions, affecting the entire body, are extremely rare and usually only occur in individuals who may have pre-existing allergies to spider bites or other insect stings.
What to Do and How to Prevent Encounters
Should a bite from a woodlouse spider occur, basic first aid measures are usually sufficient. Clean the bite area thoroughly with mild soap and water to prevent infection. Applying a cool compress or an ice pack wrapped in a cloth to the affected area for 15 minutes each hour to help reduce pain and swelling. Over-the-counter pain relievers can be taken if needed, and antihistamines may help alleviate any itching. Seeking medical attention is generally only necessary if there are signs of infection, such as worsening redness, pus, or fever, or if an individual experiences a rare allergic reaction or if symptoms significantly worsen.
To prevent encounters with woodlouse spiders, several practical steps can be taken. Sealing cracks and crevices in foundations, around doors, and windows can block entry points into structures. Reducing clutter in areas prone to dampness, such as basements, crawl spaces, and garages, makes these environments less appealing to spiders and their prey. Addressing sources of moisture, such as fixing leaks and using dehumidifiers, can also help, as these spiders are attracted to humid conditions. Maintaining a tidy yard by removing woodpiles, leaf litter, and other debris near the house further reduces potential habitats for these spiders.