Column: Cold weather spiders

Published 4:55 pm Thursday, December 13, 2007

By Staff
I readily admit to being a staunch member of the group of folks that aren't fond of spiders. I'm not as bad as some. Spiders don't send me running with shrieks of terror, it's more an annoyance thing. It drives me crazy to inattentively walk out the patio door and feel a spider web wrap around my face. The yard light next to the door draws insects and every spider in Cass County vies for door space to string up a web. You'd think I'd learn to watch out but I don't seem to. And no matter how diligently I patrol the house with vacuum hose in hand I never seem to get all the webs. There are always a couple that magically re-appear under some chair or table after the vacuum cleaner is stowed away. Even more revolting are the woolly egg sacs strung about like creepy Christmas tree ornaments.
A while ago, after the weather turned good and cold and I figured all the spiders had died or gone wherever they go for the winter, I got ambitious and swept all the webs and egg sacs from the garage and aforementioned patio area. Surely I would be good until spring. Nope. Despite the temperatures hanging steadily around freezing, give or take a little, the webs are back. Of course, spiders, like all bugs, are cold blooded and shouldn't be functional at these temperatures. You don't see mosquitoes or flies or moths buzzing around in these temperatures so what's up with the spiders? Do they have some kind of special cold tolerance talent? Curiosity compelled me to look into this.
I wasn't able to find much on this subject but it appears for the most part that spiders don't have magical winter capabilities. Many species simply die when cold weather hits, the continuation of future generations left to eggs stashed in sheltered places (like my garage!). Other species ride out the winter under leaf litter or other sheltered places in a form of hibernation where they draw their legs in and their metabolic rate decreases. With some species the adults die at the onset of freezing temperatures but newly hatched juveniles overwinter as a group snuggled in the woolly egg sac. I've heard they obtain sustenance by eating their siblings until just one or two kings or queens of the sac is left but I don't know how true that is.
However, I did find some hints that many spider species can function to a degree in cool temperatures. Those that overwinter have high levels of glycerin in their blood (yea, spiders have blood but it's clear, not red) that may act as an anti-freeze. One study in Rhode Island found that wolf spiders actually migrate to protected forest areas to ride out cold weather. This movement was far more pronounced during weeks with freezing temperatures so at least this species is mobile at near freezing temperatures.
Then there are the species that thrive during the winter in the subnivean zone. I bet you've never heard of that place. I hadn't until now. Found in some northern areas, it's a tiny, fraction of an inch layer between the ground and the snow where the snow's insulation keeps the temperature just slightly above freezing no matter how cold the air above is. Entire invertebrate communities go about their daily business in this subnivean zone. Canada reports they have at least 55 species of spiders that remain active under the snow.
Finally are the really smart spiders. They don't put up with all that nonsense of dying, cannibalism or curling up shivering under leaves. They just come into my house where it's nice and toasty and dry, string up webs in every nook and cranny, hold orgies and hang egg sacs all over the place. Carpe diem.