Wilderness Underfoot: Common house spider: a harmless guest

StoryImage( ‘/Images/Story//Auto-img-116482379832206.jpg’, ”, ‘The common (or American) house spider – Achaearanea tepidariorum with a pair of egg sacs and her most recent meal: a box elder bug. ‘);

There’s nothing to fear from this fellow traveler.

The common house spider is believed to be native to the Neotropics—but having adapted to human habitats, it’s now found anywhere we live throughout the world. It prefers the comforts of a secure shelter, and nothing beats a man-made structure. Although uncommon in nature’s great wide open, this spider is abundant in homes, garages, sheds, barns and even along fences.

With lifespans as long as a year, and an attraction to human shelters, house spiders are among the small number of arthropods you’ll find inside your home during the winter. They’re harmless to humans, and potentially beneficial when it comes to insect pests. Admirers of spiders will recognize the value of these little creatures. House spiders help in their small way by consuming pests such as flies and mosquitoes during summer months, and beetles that come indoors to winter over. You may find as many as a dozen insect corpses (empty shells, really) lying under any given house spider’s nest.

As for the cobwebs they leave behind, think of them as reminders to sweep, dust and clean the furthermost corners of your house every now and then.

House spiders are web-builders, as opposed to being wandering hunters. Their nests are nothing fancy. They simply stretch lines out in all directions, trying to set up the best trap for an unlucky insect to fly into or stumble upon. The spiders add extra lines to the spot where they sit and wait for prey.

When an insect gets tangled in the sticky web, the spider quickly assesses by the vibrations whether it is small enough to take, and then springs into action. It spins a cocoon around its prey, and then delivers a venomous bite that disables the insect and dissolves its internal organs. Over several days, it will suck out the slurry from inside the insect’s body, leaving a hollow husk. After the insect is fully drained, the spider will cut it free from the web and allow it to fall away.

The house spider will set off in search of a better location if its nest fails to yield any good catches. If you should discover one trapped in a sink or bathtub, it was probably on such a journey. With poor vision and an insignificant amount of venom, the spider is at your mercy. While arachnophobes will do what they must, there’s no harm in delivering the creature to a cellar window and letting it be.

From the Nov. 29 – Dec. 5, 2006, issue

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