Identifying potentially dangerous spiders is important for home safety. While many spiders are harmless, a few species possess venom that can cause significant reactions. Understanding how to recognize these spiders allows individuals to take appropriate precautions and distinguish between benign and dangerous species.
General Indicators of Potentially Dangerous Spiders
Certain physical characteristics can suggest a spider might be medically significant, even before specific identification. Many spiders of concern possess a distinctively shaped abdomen, often appearing more rounded or bulbous. Their legs might appear robust or have a uniform color without prominent banding or stripes.
Some dangerous species exhibit a glossy, almost hairless appearance. While color alone is not a definitive identifier, patterns such as a shiny black body or a dark marking resembling a violin on the cephalothorax are general indicators. Observing these features can help narrow down possibilities.
Key Identification Marks of Common Dangerous Spiders
Two of the most commonly encountered medically significant spiders in North America are the black widow and the brown recluse, each possessing distinct identification marks.
Female black widow spiders have glossy black bodies and a prominent red or orange hourglass-shaped marking on their abdomen’s underside. This marking can sometimes appear as two separate red triangles, or faint red spots might be present on the top of the abdomen. The female black widow’s body measures about 13 mm (0.5 inches) long, excluding legs, and they may be seen hanging upside down in their web, which makes the hourglass visible.
Brown recluse spiders are recognized by a dark, violin-shaped mark on the top of their cephalothorax, with the “neck” of the violin pointing towards their abdomen. These spiders are light to medium brown, tan, or yellowish-brown, and their legs are uniformly colored without stripes or banding. Unlike most spiders with eight eyes, brown recluses have six eyes arranged in three pairs, a unique feature requiring close observation. Their body size ranges from 6 to 20 millimeters (0.24 to 0.79 inches), including legs.
Beyond Visuals: Web Patterns and Habitats
Spider identification extends beyond observing the spider itself; web patterns and preferred habitats offer additional clues.
Black widow spiders construct irregular, messy, and tangled webs. These webs are often found near ground level in dark, undisturbed, secluded areas, such as woodpiles, sheds, garages, basements, and under eaves or outdoor furniture. They might also be found in seldom-used items like old shoes or boxes.
Brown recluse spiders do spin webs, but these are irregular and loosely constructed, primarily serving as a retreat or shelter rather than for catching prey. As hunters, brown recluses often leave their webs at night to search for food. Their preferred habitats include dry, dark, and undisturbed places like attics, basements, closets, crawlspaces, and within storage boxes, shoes, or behind furniture. Outdoors, they can be found under rocks, logs, and in woodpiles or sheds.
Immediate Steps When a Dangerous Spider is Suspected
If a potentially dangerous spider is suspected or identified, remain calm and maintain a safe distance. If the spider is indoors and needs removal, a method involves placing a cup or jar over it and sliding a piece of paper underneath to trap it. The spider can then be safely released outdoors, away from the home. It is advisable to wear gloves when handling items in areas where spiders might hide, such as woodpiles or basements.
In the rare event of a spider bite, especially if a dangerous species is suspected, act promptly. Clean the bite area thoroughly with mild soap and water. Applying a cool compress or ice pack for about 15 minutes each hour can help reduce pain and swelling. Elevating the affected limb can also be beneficial. Seek immediate medical attention if the spider is known to be a black widow or brown recluse, if severe pain, cramping, or a spreading wound develops, or if breathing difficulties occur.