Gary Larson drew a cartoon some time ago that depicted a frantic spider telling his buddies about the attack: "Here I was, snug in this shoe, minding my own business, when suddenly I was attacked by a giant five-headed monster!" A large foot lay nearby, toes up.
Hobo spiders move into houses about this time every year. And none of them ever earned a "plays well with others" comment on a report card. Hobos are large brown spiders that are cannibalistic, lousy climbers, frequently get tangled in other spiders' webs, are big eaters and live life mostly alone. No wonder they have bad attitudes.Nobody likes to see them sprinting along a baseboard at 15 to 20 inches per second. Hobo spiders, Tegenaria agrestis, are a good 11/2 inches across with thick, hairy legs. And they bite. They used to be called "aggressive house spiders" because they'll bite with little provocation.
Mature females usually sit in their tunnel webs and wait for prey. When an insect is trapped, they'll run forward, forelegs upraised, bite their meal to subdue it and run back with it into the tunnel.
Often, males looking for a date find themselves a female's next meal if they fail to signal the secret handshake, or if she's just plain in a bad mood. Both will readily eat their young, and the young will eat each other, given the opportunity. Not an Ozzie and Harriet-type family.
For years, brown recluse spiders have been blamed for bites on humans and pets, but brown recluse spiders don't live here. They are only found from the Midwest to Deep South, unless one accidentally gets transported.
The only brown recluse found in the Northwest was in Prosser, Wash., in 1978 when a moving van brought it in. Never again have we seen another brown recluse. Hobos arrived in Seattle in the 1930s and quickly spread across the Northwest.
Venom from hobo spiders produces skin injuries similar to those caused by the brown recluse, hence the confusion. The initial bite is not painful, but in about 30 minutes, a small, insensitive, hard area appears.
That will be surrounded by an expanding reddened area of 2 to 6 inches around. Within 15 to 35 hours, the area blisters. About 24 hours later, the blisters break. A cratered ulcer crusts over to form a scab.
Tissues beneath the scab may die and slough away. Sometimes surgical repair is called for, according to Washington State University Extension Bulletin 1466. If you are bitten, see a doctor right away.
T. agrestis have not caused a death hereabouts, and in Europe, their homeland, there are few records of bites from these spiders causing medical problems.
That might be because Europeans have learned to take precautions. Always wear gloves when working in dense, low brush or places you cannot see into clearly. That goes for moving firewood, too. Tegenaria prefer cool, moist areas such as basement window wells and crawl spaces. Inspect your door and window casings for gaps. Fill all holes, including those surrounding water pipes and electrical lines, with expanding foam.
Before you bring in firewood, look it over for spiders or egg sacs. Keep woodpiles away from the house. Use a good vacuum indoors to remove spiders and webs from corners and nooks. Put the bag in a plastic bag and throw it in the trash.
Outside, you can treat the first three feet of your foundation and the interface between the siding and wall with man-made pyrethrin copies such as Intercept, (permethrin), cypermethrin, diazinon or dursban.
Inside, a shoe is recommended. Fly swatters give you a little more reach. Sticky traps designed for spiders might also be effective. And check your shoes before you shove your foot in.