It is common to encounter a spider indoors, a natural occurrence that is usually more startling than concerning. Most spiders that reside indoors are harmless to humans, playing a subtle role within the home environment.
Reasons for Indoor Presence
Spiders enter homes driven by fundamental needs for survival, primarily seeking shelter and food. Harsh outdoor conditions like extreme cold, heat, or heavy rain prompt spiders to move indoors for stable temperatures and protection. Homes offer a consistent environment, making them attractive refuges.
The presence of other insects within a home is a significant draw for spiders, as these insects represent a consistent food source. Spiders follow their prey, with common household pests like flies, mosquitoes, and ants providing ample sustenance. Accidental entry also accounts for many indoor spider sightings; they might wander in through open doors or windows, or hitchhike on items brought inside. Some spiders may also enter homes for mating.
Understanding Common House Spiders
Among the many spider species, several are frequently encountered indoors. The American house spider (Parasteatoda tepidariorum) is common, recognized by its tangled webs in corners or under furniture. These small spiders, yellowish-gray to brown with mottled markings, are harmless to humans, biting only if threatened. They serve as natural pest controllers, preying on various household insects.
Cellar spiders, often mistaken for daddy longlegs, are widespread indoor residents. They prefer damp, dark areas like basements and crawl spaces, spinning loose, irregular webs. Cellar spiders are beneficial, consuming other insects and spiders (including black widows) without posing a threat to humans.
Jumping spiders, with compact, colorful bodies and large front-facing eyes, are active daytime hunters that do not build webs. They stalk and pounce on insects, using exceptional vision and powerful legs. While they can bite if provoked, their venom is not dangerous to humans, causing only mild, localized reactions.
Wolf spiders are larger, hairy spiders, primarily outdoor hunters that may enter homes during colder months. They do not spin webs for hunting but actively pursue their prey. Though their size can be alarming, wolf spiders are not aggressive towards humans and their bites are not harmful.
Preventing Future Visits
Minimizing indoor spider presence involves addressing entry points and reducing attractive elements. Sealing cracks and gaps in foundations, walls, and around windows and doors can prevent spiders from entering. Installing or repairing window and door screens creates an effective barrier against spiders and their prey.
Managing clutter inside and outside the home removes potential spider hiding spots. Regular cleaning and vacuuming removes webs and egg sacs, discouraging spiders. Reducing indoor insect populations (a spider food source) can be achieved by keeping food sealed, disposing of trash properly, and cleaning up crumbs. Trimming back vegetation from the house perimeter and using yellow or sodium vapor lights outdoors can reduce insect attraction, decreasing spider activity near the home.