It happens every year at this time. Just as clear skies and warm weather spark a human exodus from homes into the great outdoors, spiders seem to migrate in the other direction, taking up residence indoors. There are two primary reasons for spiders to invade a home or apartment: love and food.
The reason indoor spiders are more numerous in spring and early summer is love. Well, reproduction really. Spring is when spiders breed and male spiders go in search of females. That wanderlust (or just plain lust) sends them everywhere, including homes, looking for mates with whom they can swim in the genetic pool. The quest for genetic immortality makes spiders more active, less cautious and easier to spot.
A little later in the season, tiny spiders hatch and start scurrying about in search of food and shelter. If they do not starve, are not eaten and are not killed by their siblings, the small spiders that escaped human notice become big spiders that are noticed. Put simply, fewer spiders means bigger spiders.
Spiders are more likely to set up residence in homes that offer a steady supply of their food sources: flies, cockroaches and other insect pests. The best way to keep spiders out of a home is to keep the floor swept clean and to wipe up food residue before it attracts spiders’ prey. It also helps to get rid of cardboard storage boxes, which draw cellulose-eating pests such as termites, and replace them with plastic containers.
Spiders do not always invade a home for love or food, but may be brought indoors against their will. Some are carried indoors inside of pieces of firewood where they holed up for the winter. If they can scamper away before the log gets tossed onto the fire, they may decide they like it indoors better than out.
To keep spiders from entering a home in the first place, maintain a clear space between the foundation and mulch, plants or debris. Spray insecticide in cracks and holes that spiders might squeeze through to gain access. Perimeter treatments put down to keep insects out of a house may help to repel spiders, too.
Most humans have a built-in fear of spiders, but there is seldom reason to freak out if one is spotted indoors. They are solitary creatures and will flee humans unless they have no way to escape. Nor are they often as dangerous as they are made out to be.
All spiders are venomous but few have enough venom or venom that is toxic enough to cause more than a rash or welling at the site of the bite. The brown recluse and the black widow are two of the few species that require real caution.
The brown recluse has a particularly bad reputation, but the danger is overblown. Start with the fact that not every brown spider is a brown recluse. Its habitat is limited to central and southern U.S. from Texas to the Florida panhandle. True brown recluses are brown all over their body except for a distinctive violin-shaped mark on the abdomen. (Some people call them fiddlebacks.) A bite from a brown recluse can damage tissue at the injection site, but only in rare circumstances, and there has never been a verified death.
The black widow, on the other hand, is truly dangerous. There are several species native to the U.S., all of them dark black with a red hourglass mark on the underside of their abdomen. The black widow’s bite starts out feeling like a pinprick at the injection site but in a manner of hours can lead to excruciating pain throughout the body. Most victims recover in two or three days, but the bite can be fatal if the victim is young, elderly or has high blood pressure. Bites can be treated with antivenin shots.
Once spiders come indoors, they are hard to get rid of. It is difficult to poison them because they will not consume inert bates set out for ants and roaches. Their long legs mean they do not drag their bodies along the floor, which keeps their vital organs out of contact with insecticides sprayed on surfaces.
The best approach is to deny them a reason to stick around. Even if spiders invade a home in search of love, they will not stay if there is no food.
By J.W. Huttig