Wolf Spiders in the House

Wolf Spiders

What is the big hairy spider running across my floor? In this region, most often a wolf spider. They are among the largest spiders homeowners see indoors, with bodies up to an inch long and a leg span that can reach two to three inches. They are brown or gray with darker stripes along the body, stocky, hairy and fast. They do not build webs to catch prey. They hunt on foot, which is why you see them on the floor rather than in a corner.

Wolf spiders live outdoors on the ground. They hunt at night through leaf litter, mulch, grass, firewood and the gaps around a foundation, and they hide by day under stones, boards and debris. Their eyes reflect light, so a flashlight passed across a lawn at night often picks up small green sparks in the grass. That is them.

Indoors, they arrive in a pattern. As nights cool in September and October the insects they hunt move toward the warm foundation, and the spiders follow. They come in under garage doors, through the gap at the bottom of an exterior door, through crawl space vents and up through the openings around pipes. Once inside they wander along the floor, usually along walls, and end up in basements, garages, bathrooms and behind furniture. A house with a damp crawl space and a worn door sweep sees more of them than a house without.

Wolf spiders are not a medical concern. They are shy, they run rather than confront, and a bite, which is uncommon, is comparable to a bee sting. They are often mistaken for brown recluses because both are brown, but a wolf spider is far larger, distinctly hairy and striped, while a recluse is small, plain and smooth. A female carrying a round egg sac or covered in dozens of tiny spiderlings is also a wolf spider; no other spider here does that.

Our approach treats the routes rather than chasing individual spiders. The inspection looks at door sweeps, garage door seals, vent screens and utility penetrations, and at the ground conditions around the foundation that hold the insects wolf spiders hunt. The technician treats the perimeter and the entry points, and the same perimeter treatment that lowers the general insect population lowers the food supply. Clearing leaf litter and mulch away from the foundation and fixing the door sweeps does the rest. The fall migration will still bring a few through. The service holds it at the lowest practical level.