After the monsoons start in fall, spiders seem to appear inside homes across the Northwest.
“We get a lot of that in the fall,” said Beth Chisholm, a master gardener with the Washington State University Extension in Whatcom County. “We get a lot of people who bring in spiders out of curiosity or concern.”
Chisholm said confusion arises because the harmless common giant house spider closely resembles the hobo spider, which has a venomous bite. She said the giant house spider is the classic brown spider with extremely long legs that give it a massive a appearance.
“These are the two spiders that get mixed up all the time,” Chisholm said. Also common in Western Washington is the orb weaver.
“When you see those beautiful webs, and they’re heavy with dew, that’s usually what people see in the fall. Nine out of ten times the orb weaver is the one who spun that classic web. Not inside, but in the crotch of a tree or a fence,” Chisholm said.
Why do we see spiders indoors in fall and winter? It’s not well known, she said. But they could be seeking a warm place to live out their days after mating and laying an egg sac.
Holly Roger of the local outdoors education program Wild Whatcom said all true spiders are arachnids and have two parts – a cephalothorax (fused head and thorax) and an abdomen; eight jointed legs; and have up to eight eyes, depending on their species. All make silk, but not all make webs.
“Generally, female spiders have bigger abdomens than males,” Roger wrote in an email. “I explain this to families as the mamas have big baby bellies. Male spiders tend to have smaller abdomens (sometimes significantly) and have enlarged pedipalps that look like boxing gloves. These emerge from their cephalothorax near their mouth and are sometimes mistaken for an extra pair of legs.
“Harvestmen, or ‘daddy longlegs,’ are not true spiders, but they are arachnids,” Roger wrote. “They only have one body part, but do have eight legs. A big myth among kids is that they are highly poisonous, but they aren’t. They eat decomposing plant and animal matter.”