Friendly, neighbourhood spiders

It’s September in Edmonton. These are some of things you hear this time of year: It’s getting dark pretty early, eh? The Walterdale Bridge looks pretty rad. And, I’ve never seen a spider that size before!

As sure as the days darken and as sure as the bridge is our new landmark, the end of summer means stumbling across spider webs and wondering if there’s an invasion of creepy crawlies under way.

“The spider you are seeing is not a tropical invader,” says Peter Daly, a Biological Sciences Technologist with the City of Edmonton’s pest management lab. “It’s probably just your friendly, neighbourhood orb weaver.”

Daly explains there are more than two dozen species of orb weaver from Alberta. One of the most common varieties around houses (Araneus gemmoides, for all you Latin speakers on the web) is called the cat-faced spider because the projections and markings on the spider’s abdomen look vaguely like the ears and face of a cat.

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Other varieties around these parts are the shamrock spider (Araneus trifolium), the marbled spider (Araneus marmoreus) and the cross spider (Araneus diadematus).

These spiders build large, orb-shaped webs in gardens and along the sides of buildings and fences.  They thrive when they build their nests near a light left on overnight.  In late summer, the female spiders begin to grow quite large and people start noticing the spider that has been living quietly, minding its own business, in the corner all summer.

The orb weaver spiders are quite harmless, says Daly. Timid, even.

“Typically, they won’t bite unless severely provoked,” he says. “It would probably take a deliberate attempt at causing them physical injury to get them to bite, and even then their relatively weak jaws may not be able to penetrate skin.”

And why provoke these little friends anyway?

Orb weavers help your garden.  They eat a wide variety of pest insects, reducing the need for pesticides. While they travel far and wide outdoors on the wind after hatching, they are quite sedate as adults, and typically remain at their web sites (sorry, we couldn’t resist) unless disturbed. Even then they will only attempt to build a web somewhere else as soon as possible, so they won’t be crawling around, deliberately trying to enter houses. Indoors, they tend to do quite poorly. No food, no drink, no future.

If you really feel you must get rid of the spiders, try re-locating them.  Sweeping their webs with a broom may discourage them from building again in that location.  They are easy to capture in a jar by simply holding the jar under the spider and slowly lowering the lid towards them from above.  

If you wish to keep these spiders out of sight (and out of mind), consider turning off your porch light at night. Spiders build webs in areas that have considerable insect traffic, so by not attracting insects to the light, the spiders will be more likely to build webs where you can’t see them as easily. The dark web, so to speak. :)

While Daly grabs your attention in his web of spider information, there is one more spider he wants to introduce to you. The grass spider. (Agelenopsis spp.)

Grass_Spider_-_Agelenopsis_species_possibly_pennsylvanica-,_Vernon,_British_Columbia

Like the orb weaver, these spiders are very common, quite harmless and, like all spiders that call Edmonton home,  not prone to biting.

Grass spiders are closely related to the European house spider (Tegeneria domestica), a common inhabitant of Edmonton basements.

Their webs are sheet-shaped affairs at or close to ground level, with a little tube at one end that they hide in. The webs are not sticky, and simply act as an extension of the spider’s sense of touch. Get this: when an insect walks across the web, the spider feels the vibrations, even recognizing the difference between a prey insect and something else, and zips out at lightning speed and grabs it with its fangs.

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This time of year, adult males leave their webs and wander about in search for females, which puts them in contact with people more often than other times of year.

By the way, all of our local spiders are quite harmless. No matter what you find in your yard or garage spider-wise, you have nothing to fear.

If you have any other questions, get in touch with Peter at: peter.daly@edmonton.ca

This is him:

peterdaly

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3 Comments
  1. Soumalya Ghosh
    1 month ago

    ‘web sites’…. Lol you are funny. I never thought I would say that on an article about spiders.

  2. Carrie
    1 month ago

    You have stated that in our region of Alberta, most all spiders are harmless.
    I am curious to know what type bit me? On the tip of my big toe I received a nasty bite and it swelled and festered for at least 3 weeks. The swelling was so severe that 1/2 my nail popped off. It was extremely uncomfortable. Painful and very itchy

  3. Nicole
    1 month ago

    Do these seem more prevalent lately? I used to see a few in years past but now I get hatched egg sacks 2-3x a year on my patio furniture and these guys grow so big! There are just to many to enjoy sitting outside anymore. I hate to kill them but it’s either them or me, lol. Any tips to not have so many? I’ve tried sweeping them away and even using spray at times but they come back weeks later!

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