Every summer, like clockwork, the giant house spider emerges from the shadows. From July through September, males abandon their damp basements, sheds and storage closets, venturing boldly into kitchens, bathrooms and living rooms in search of mates.
They don’t tiptoe either. These golf ball-sized sprinters are the biggest spiders you’ll find in Oregon homes, and among the fastest. Blink, and one might already be across the wall, under the couch or scuttling across the floor.
Giant house spiders aren’t rare — they’re one of more than a dozen species you might see indoors. But they’re the ones most likely to make you jump, freeze, or reconsider why you ever went barefoot.
A giant house spider (Eratigena duellica, formally known as Tegenaria gigantea and T. duellica) in Portland Thursday, Sept. 5, 2024. The spider measured well over three inches from leg-tip to leg-tip.Mark Graves/The OregonianKey details about Oregon’s largest arachnid:
Size: Up to 4.7 inches from leg tip to leg tip, about the size of the palm of your hand. Females have larger bodies while the males have longer legs.
Vision: They have eight eyes of equal size stacked in two rows with hundreds of visual cells.
Description: Both males and females are medium to dark brown with matching markings and blatantly hairy long legs.
Dangerous?: Though their bite is venomous, it is harmless to humans and pets and unlikely to ever happen. They can be docile and used for hands-on demonstrations. According to the Department of Agriculture, most people only receive one or two bites from giant house spiders in their entire lifetime.
Lifespan: They reach maturity within a year and live just a few years. Males generally die soon after mating, while females over-winter into the next year with stored sperm producing egg-sacs in spring.
Distribution: They’re found in the Pacific Northwest and Northeast of the U.S. and all over central and northern Europe. The spider was accidentally introduced to British Columbia by humans about a hundred years ago and has since then flourished. Over time, the arachnid has evolved to survive in human homes.
Reproduction: One egg sac will produce around 60 spiderlings. If food is unavailable, they will resort to cannibalism.
Speed: They’re fast. Up until 1987, they were considered the fastest spider in the world by the Guinness Book of World Records, darting at speeds of about 1.5 feet per second.
Diet: All bugs, including bedbugs, cockroaches, earwigs and flies.
Additional good-to-know Oregon spider facts:
Experts consider giant house spiders beneficial organisms that should be left alone as much as reasonably possible.If you find a spider in your sink or tub it didn’t come from the drain. They come down the walls seeking water.If your house has spiders then your house has other insects, which is what draws spiders into your home.House spiders are commonly mistaken for wolf spiders. Wolf spiders prefer the outdoors in warm and dry climates.They’re more commonly encountered than hobo spiders.Their funnels also serve as a place to retreat from predators.While females only leave the safety of their funnel to feed, males can be found wandering for females in open spaces.The brown recluse, a fairly well-known venomous spider that occasionally bites people, does not live in Oregon, despite reports to the contrary. Black widows do live in Oregon.
Further info:
Check out the Spiders of Portland identification guide, or follow instructions to submit a spider for identification to the Oregon Department of Agriculture. The website spiders.us has photos of males and females of 39 species found in Oregon, and this OregonLive guide, which goes into more detail.
There is no easy way to prevent spiders from entering your home. The best thing you can do is keep windows closed, use insect screens and fill any exterior gaps.
Sources: Natural History Museum in London, Portland State University, Washington State University Burke Museum, British Arachnological Society and Oregon Department of Agriculture
— Mark Graves/The Oregonian
503-860-3060
@mark_w_graves
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