Brown recluse webs are often hidden because they aren’t built to catch prey like those of other spiders. Brown recluses prefer dark, hidden places, such as attics or storage spaces, where they might hide in boxes or piles of clothing. Since they mainly build webs in rarely-disturbed areas, the most likely sign of an infestation is seeing the spiders. However, they are fast runners and excellent at hiding, making it difficult to notice their presence.

Brown recluses are venomous spiders but they are not naturally aggressive toward humans. They rarely bite and only do so when threatened—even accidentally—by someone unknowingly reaching toward their webs or catching them moving around at night. If you think you’ve been bitten by a brown recluse, it’s important to correctly identify the bite. Bites from other spiders or insects are often mistaken for those from brown recluses.

1. You might not notice a brown recluse bite at first because it’s not always immediately painful

2. Minor stinging and visible fang marks are early symptoms

3. Later, severe pain and itching can develop

4. Other possible effects include fever, nausea or muscle pain

5. The venom can create a small blister around the bite that might begin to spread

The severity of the reaction varies from person to person but, if you suspect you’ve been bitten by a brown recluse, you should seek medical attention as soon as possible. You can also help reduce swelling with a cool compress and clean the bite with mild soap and water.

Brown recluse spiders can enter a home if they are attracted by the presence of prey insects or if they are searching for places to build a web. Woodpiles, rubble and cluttered landscaping around a house are attractive hiding places. Indoors, they’ll look for boxes, piles of books or newspapers, shoes, stored fabrics and other dark, little-used areas. These locations are often in attics, crawl spaces, garages and sheds.

Brown recluse spiders are not native to the entire U.S., but live most commonly in the southern and southeastern states. They can still move to other places within boxes or on trucks, though, and take up residence in and around homes.

Their webs are off-white or gray in color, disorganized in shape and often built close to ground level. Once they’ve entered a home, brown recluses will hunt other insects and lay their eggs in the early summer months.