Called alternately the sowbug spider, woodlouse hunter, or the dysderid, this spider is very common throughout the U.S., primarily in the East from New England down to Georgia, then west to California. Outside the U.S., it is common in Australia, northern Europe, and England. Although it lives outside to hunt its prey, it may come indoors in the fall for shelter.
The sowbug spider has a very distinctive appearance:
- The female is generally about 1/2- to 3/4-inch long and the male is generally smaller, at less than 1/2 inch.
- Colorful with purplish-brown upper body parts, a grayish-white abdomen and orange legs.
- Most spiders have 8 eyes, but the dysderid has only 6 eyes – that are set in an oval shape.
- Very large, thick mouthparts with large, forward-projecting fangs. It uses its scissor-like fangs to capture and hold its prey, then uses a single fang to spear an arthropod’s soft belly, kill, and eat it.
- It is sometimes confused with the brown recluse spider, because of its coloring and some similarity of features. Its orange legs are the key differentiating characteristic of the sowbug/woodlouse spider.
- It feeds primarily on sowbugs and pillbugs (which are also called woodlice) – thus its name. It will also feed on other arthropods which it happens to come across in its hunting.
- The sowbug spider is nocturnal and hunts actively at night.
- Commonly found outside, this spider lives in city gardens, fields, and forests. It will harbor under rocks, stones, logs, debris – or even in basements. It may also find a home in the rotting wood or a deck, porch, or other outdoor wooden structure. Essentially, anyplace that is warm and moist – and attractive to sowbugs, pillbugs, woodlice.
- Although this spider will harbor in a silken web beneath rocks, etc., it does not spin its web to capture prey. Rather it goes out hunting for its food.
- When it does venture indoors for shelter, it will commonly seek harborage in hidden cracks and crevices … until it is ready to hunt.
The sowbug spider may bite if it is handled, but even if it does, its bite is rarely very painful. Although all spiders have venom, that of the sowbug spider is generally unlikely to cause any real issues beyond possible short-lasting minor pain, itchiness around the area of the bite, or possibly some inflammation.
These symptoms can be treated with over-the-counter products if needed. However, if the bite is exceptionally painful, continues to be painful or exceedingly itchy for a number of days, or develops a seeping or ulcerous sore, the bitten person should seek medical attention. The spider may have been misidentified or the person could be having a greater-than-typical reaction.
The best method of controlling the sowbug spider is taking measures to reduce the attraction of your home and property, by decreasing the presence of prey and the harborage sites of both the spider and its prey (damp areas of debris, woodpiles, leaf litter, mulch, etc.), reducing standing water (which also helps reduce mosquito breeding sites).
Spiders that do get into the home can be captured on sticky traps, which is a good control for them. Again, increasing sanitation decreasing clutter in the home (e.g., papers, boxes, bags, etc.) that attract and provide harborage for spiders and pillbugs will help reduce the presence of spiders in the home.