Keeping Bugs Where They Belong

3 Things You Need To Know About Triangulate Cobweb Spiders

3 May 2016

Judy Lute

Triangulate cobweb spiders (steatoda triangulosa) are one of the most common spiders in North America, and they may infest your basement or garage. Here are three things you need to know about triangulate cobweb spiders.    

How are triangulate cobweb spiders identified?

Triangulate cobweb spiders are small and can be easily overlooked until many of them are present. Their round bodies are 1/8 to 1/4 inches long. Their abdomens are brown with white and yellow markings; these markings may be triangular or irregular. Their legs are yellow, and each joint of their legs is brown.

Because of their size and body shape, you may think they're brown widow spiders. This isn't an uncommon mistake: spiders in the steatoda genus are called false widow spiders because of this similarity. While they may look similar at first, triangulate cobweb spiders don't have an hourglass marking on their undersides.

Why are triangulate cobweb spiders pests?

These spiders are pests because they're well-adapted to live among people. They're abundant both inside houses and on the exteriors of houses. While these spiders aren't dangerous, their infestations can be very distressing.

They're able to feed on many kinds of pests that are found in houses, like ants and pillbugs, and they can even eat other spiders. They aren't eaten by other household spiders—they have been reported to share nooks and crannies with the dangerous brown recluse spider—so their numbers are only limited by how much food is accessible.  

How can triangulate cobweb spiders be controlled?

To get rid of these spiders, knock down their webs and then crush the spiders. You can also kill them by sucking them up with a vacuum. Pesticides can also be used. Residual pesticides are ideal because they keep killing over time while non-residual sprays only kill on contact.

It's also important to get rid of their egg sacs. These egg sacs may be attached to the ceiling or to spider webs. The sacs are about 6 millimeters across, and if you look closely, you'll be able to see the spider eggs inside. Pesticides may not pass through the protective sac to destroy the eggs, so it's best to crush them to ensure that the eggs are all destroyed. Take the crushed egg sac outside; just in case any eggs survived, you want them to hatch outside, not inside your house!

If you're having trouble keeping triangulate cobweb spiders under control, hire a pest control company (such as pest control by Peninsula Pest Control) to help you.

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