Though spiders produce feelings of fear and revulsion in many people, only a few species are truly dangerous to humans. In the home or school environment, three species are cause for concern: the black widow, brown recluse and aggressive house/hobo spider. These spiders will usually only bite if provoked, but their bites can cause severe reactions, possibly even death in rare cases.
Nesting and hiding places for three problem spiders
Black widows like dry, undisturbed places such as lumber and rock piles, stacked pots or baskets, rodent burrows, water meters, the underside of bricks and stones, and dry crawl spaces. Females stay in the web. Brown recluse spiders prefer undisturbed places for their webs, hunt primarily at night and will take refuge in clothing and bedding. They are often found in unused closets and storerooms, behind furniture, and in baseboard cracks and crevices. Outside, they can be found in foundation cracks, cracks in the soil and window wells.
Aggressive house spiders prefer dark, moist places with cracks and crevices for their funnel-shaped webs. They are poor climbers and are rarely seen above ground level. Males wander (especially during summer months) and sometimes become trapped in clothes, toys, bedding, or shoes. Inside, this spider is likely to be found in basements and on ground floors between stored items, in window wells, in closets and behind furniture. Outside, it can be found in areas similar to both the black widow and brown recluse.
Avoiding spider bites
Use caution when working near common nesting places of the three dangerous spiders. Gardeners and custodians should be careful about where they put their hands when doing outdoor work, and wear gloves and a long-sleeved shirt when working around woodpiles or other items that are likely to harbor the spiders.
Make sure students and staff can identify any dangerous spiders in your area and know their likely nesting and hiding places. Teach children not to tease spiders in their webs or poke at them, and not to put their hands in dark crevices without looking first. Explain the dangers of spider bites without exaggeration to avoid unnecessary fears. Tell students and staff that the black spiders they see walking around are not likely to be black widows because the females (males are not dangerous) do not travel away from their webs.
Minimizing spider infestation
Non-chemical control is usually considered most effective when dealing with spiders. The following recommendations will help to eliminate hiding or harborage sites and exclude spiders from buildings:
- Store boxes off the floor and away from walls and seal them tightly with tape to preclude spider access.
- Move stacks of firewood and piles of debris or rock away from schools and elevate them when possible.
- Remove vegetation from sides of buildings and keep grass cut.
- Maintain tight-fitting screens in windows and seal cracks in walls or other entrance sites.
- Keep attics and basements ventilated to reduce moisture, thus reducing the amount of prey insects available as a food source for spiders.
Removing webs and egg sacs of existing spiders with a vacuum discourages subsequent infestation. If a dangerous spider is vacuumed up, seal the vacuum bag in a plastic bag and place it in a freezer for 48 hours to kill the spider. In the case of the brown recluse, which prefers to nest in dark, undisturbed areas, use extra caution when inspecting boxes of paper or other items stored in closets. Wear leather gloves while searching through stored items.
First aid for spider bites
Wash the area around the bite, calm the victim and consult a doctor as soon as possible. The very young, the elderly and sick, and people with high blood pressure are particularly at risk. If possible, capture the spider so it can be taken to a doctor. Proper treatment may depend on identifying the species. Even the squashed remains of the spider can be useful for identification purposes.