Our apartment has had spiders in it all year, but they’re very tolerable little guys: for the most part, they just hang out in the corners, keep to themselves, and don’t go roaming about in surprising ways. Come autumn, though, that’s when the big guys come-a-callin’. The aptly (but dramatically) named Giant House Spider (Tegenaria gigantea) ventures indoors this time of year, not to get out of the cold, as is the common misconception, but to look for love. The lady spiders prefer to live outside, though, so wandering into a house is usually unintentional, and a detriment to their dating strategy. They’re not aggressive, thank goodness– they’re just startlingly large, even to me, who finds that sort of thing interesting. As it turns out, they’re actually kind of beneficial to have around: it seems they discourage Hobo spiders from settling into your house, by either out-competing or just straight-up eating them. So, it seems it’s a bigger, harmless spider that chases away or eats its smaller, more troublesome cousin.
I suppose I should point out that “spider season” is rather erroneous too– that’s just a name I applied to this period of late summer that correlates to their increased visibility. According to Rod Crawford’s super helpful site (he’s the Curator of Arachnology at the Burke Museum), this time of year is actually the hardest time (locally) for spiders, since it’s the dry season. It just happens to be the time during which the “large conspicuous spider species… are mature”.
Anyway, if you want to read more about the spiders of the Pacific Northwest, check out some of the above links, as well as this helpful guide to spiders (PDF) provided by Woodland Park Zoo.