The onset of hot weather, especially on the heels of a warm, rainy period, increases the activity level of spider in town and in the field. Some of those spiders are more apt than usual to be encountered during a routine day. A moment of carelessness could result in a painful bite and potentially life-threatening bite.
Earlier in the week, a doctor from Providence Centralia was quoted by a Chronicle reporter as urging us to beware of being bitten by black widow or brown recluse spiders, and “they were everywhere.”
The good doctor was partly right; we need to be keenly aware of some of the spiders that share our space here in Western Washington. Unfortunately, he had his species wrong. (In all fairness, the doctor was from an area far from Washington where those other spider species are common.)
There are no populations of black widow spiders in our region, and there are no brown recluse spiders at all in Washington. In fact, the only specimen of a brown recluse ever collected in this state was two decades ago at the entry station near Spokane. A single brown recluse was found by state agricultural inspectors in a trailer filled with household goods from Indiana. No other individual of that species has ever been recorded in Washington State.
The potential for encountering a very dangerous house spider, sometimes called “hobo” spider, is very real, however, and demands your watchfulness at all times.
Three examples of the house spider (Tegenaria subsp.) are established in Lewis County and all of Washington. The most dangerous of these is the “aggressive house spider,” Tegenaria agrestis. This spider is extremely dangerous and the bite may do enormous, life-threatening damage.
The others include the giant house spider, Tegenaria gigantis, and the common house spider, Tegenaria domestica. The latter two aren’t particularly aggressive and are reluctant to bite unless cornered or squeezed.
The “hobo,” or aggressive house spider, by contrast, will bite with little provocation. In one local case, a carpenter was bitten on the ankle and before treatment could start the wound began to darken and swell. Soon a systematic destruction of cells called necrosis began.
After nearly two years of treatment the young man’s leg was removed just below the hip to save his life.
These house spiders may be encountered in or around the house, outbuildings, or woodpiles and other dry, waste wood. The first sign of the house spider will be a “tunnel web,” the distinctive form this animal’s insect trap takes.
House spiders are large, usually at least ¾ of an inch across counting the legs, are a dull brown with darker legs, and have a tan pattern on the lower part of their back. If you see one, kill it. They are non-native immigrants, dangerous, and kill beneficial garden spiders and other harmless species.
These spiders will be about for the rest of the year and beyond, so visit one of the northwest spider web sites and look at several images of house spider specimens. It’s a good way to become familiar with a dangerous rascal that may just someday share your home.
