We've all played host to freeloading roommates — the type that's obsessed with silk and is really good at lurking in dark corners to eavesdrop.

Spiders. These eight-legged critters seem to come out of the woodwork en masse in late summer and fall — but why? We asked Josh Vlach, an entomologist with the Oregon Department of Agriculture, to untangle the web of facts and fictions.

The uptick

While you may notice more spiders right now, that doesn't necessarily mean there's been a boom in their numbers. Vlach said many spiders are simply getting bigger and building large enough webs to be noticed. Males are also wandering around looking for mates. Aww. Later in the season, the females will seek out spots to shelter through the winter — and our homes are attractive options.

So many species

According to Vlach, there may be approx. 500 spider species in Oregon, but most that enter our homes are actually native to Europe. An average of 10 new invertebrate species settle into Oregon every year — and one in five is a known pest (including the brown widow). See the spiders commonly found in Portland.

The giant house spider (pictured above) + the hobo spider are two of Portland's most common European spiders. | Photo via Oregon Department of Agriculture

Knowing friend from foe

Thankfully, our part of the world isn't home to any harmful spiders other than the black widow (which is native to Oregon but uncommon in Portland). All true widow spiders have a distinct red-to-orange hourglass on their underside, making them easy to ID. And no, the brown recluse doesn't dwell here.

Spider-proofing

To prevent visits from unwanted arachnid house guests, make sure your home is as well-sealed as possible by caulking gaps + cracks and making sure there are no gaps under doors. Keeping structures and vegetation from touching the exterior of your home will also help.