Spiders in Alberta

What spiders live in Alberta?

Alberta runs from short-grass prairie and badlands in the south-east to boreal forest and the Rocky Mountain front in the north and west, and its spiders sort themselves along that gradient. Sheet-web weavers and small wolf spiders of the genus Pardosa are the most abundant animals on the ground almost everywhere, while the species people actually notice are the large, late-summer orb weavers and the hunters that come indoors when nights cool.

Contrary to the idea that spiders avoid the cities, Calgary and Edmonton are full of them. The cross orb weaver, a European import also called the garden spider, is one of the commonest large spiders on Alberta porches and fences, and the native shamrock orb weaver turns up in gardens and hedgerows with an abdomen that ranges from cream through orange to deep purple-brown.

Which Alberta spiders are dangerous?

One species, and only in part of the province. The western black widow lives in the hot, dry south: the badlands around Drumheller and Dinosaur Provincial Park, the Medicine Hat and Lethbridge districts and the coulees of the Milk River country. The mature female is glossy black with a red hourglass on the underside of the abdomen and hangs in a strong, irregular web close to the ground, inside rodent burrows, rock cracks, junk piles, culverts and the undersides of farm equipment. Her bite can cause severe muscle cramps, sweating, abdominal pain and hypertension. Antivenom exists but is rarely needed, and deaths are extremely unlikely with modern care.

The hobo spider is listed as dangerous on most older Alberta pages, and that reputation has collapsed under scrutiny. The evidence linking it to necrotic wounds was never reproduced, and the US Centers for Disease Control removed it from its list of venomous spiders of concern in 2017. It is an introduced European funnel weaver, most firmly established in British Columbia and the Pacific Northwest, and it cannot be told apart from harmless relatives without a microscope.

There are no recluse spiders in Alberta. Loxosceles is not established anywhere in Canada, so a brown recluse diagnosis in Edmonton or Calgary almost always turns out to be a bacterial skin infection or another medical condition.

Where you meet them

In and around buildings

The barn funnel weaver is the classic Alberta indoor spider, spinning a flat sheet with a funnel retreat in basements, garages, sheds and window wells; it is harmless and is the species most often mistaken for the hobo. Cellar spiders occupy corners, and the bold jumping spider, black with a bright abdominal triangle and iridescent green jaws, hunts by daylight on sunny walls, fence rails and deck boards in the south of the province.

Water edges

Alberta's largest spiders live beside ponds, sloughs and slow rivers. The striped fishing spider waits at the waterline with its front legs on the surface film, reading vibrations, and can run across the water or dive under it. The dark fishing spider is largely an eastern species that lives further from water, so most big Dolomedes photographed in Alberta are the striped fishing spider or the six-spotted fishing spider of marsh margins.

Grassland and gardens

The goldenrod crab spider ambushes bees and flies on flower heads, and the female can switch between white and yellow to match the bloom, a change that takes days rather than seconds. Wolf spiders patrol open soil at night; a headlamp held level with your eyes lights up their eyeshine across a lawn, which is covered in our guide to wolf spiders.

Spider season in Alberta

The original version of this page said Alberta spiders are at their most noticeable in spring. In practice the peak is at the other end of the season. Spiders hatch or emerge small, feed all summer and reach full size in August and September, which is when orb-weaver webs suddenly appear across doorways and when wandering males come indoors looking for mates. The first hard frosts end it.

Winter is survived rather than escaped. Many species overwinter as eggs or part-grown juveniles under leaf litter, bark and snow, accumulating cryoprotectant compounds that stop ice forming inside their tissues; a stable snowpack is far better insulation than a bare cold snap. The strategies are described in our guide to where spiders go in the winter. Bites of any kind are rare here, and most reported spider bites in the province turn out to have another cause.

Easy mix-ups in Alberta

The most consequential one is the false black widow and its Steatoda relatives, which are dark, glossy and round-bodied like a widow but lack the red hourglass, showing at most a pale crescent at the front of the abdomen. They are harmless, and they are found far more widely across Alberta than true widows.

The second is funnel weaver against funnel weaver: barn funnel weavers, grass spiders and hobo spiders all build the same sheet-and-funnel web, and no photograph settles the question. The third is not a spider at all. Harvestmen, with one fused body section, no silk and no venom, are reported as spiders every autumn, and so are the leggy crane flies that drift through open doors in September.

Common Spiders in Alberta

• Cross Orb-weaver Spider
• Bold Jumping Spider

Big Spiders in Alberta

• Striped Fishing Spider
• Dark Fishing Spider

Dangerous Spiders in Alberta

• Western Black Widow Spider
• Hobo Spider

Most Venomous Spiders in Alberta

Comb-footed Spiders

Cobweb SpidersWestern Black Widow (Latrodectus hesperus)Identify the western black widow (Latrodectus hesperus): the red hourglass, the male and spiderling patterns, its web, range and how serious

Funnel Weaver Spiders

Funnel Weaver SpidersHobo (Eratigena agrestis)Identify the hobo spider (Eratigena agrestis): size, chevron abdomen, funnel web, where it lives, and why its bite is not considered necroti

Less Venomous Spiders in Alberta

Orb-weaver Spiders

Orb WeaversShamrock Orb Weaver (Araneus trifolium)Identify the shamrock orb weaver (Araneus trifolium): size, the white-dotted globe abdomen, banded legs, its web and retreat, range, season Orb WeaversCross Orb Weaver (Araneus diadematus)Identify the cross orb weaver (Araneus diadematus) by the white cross on its abdomen: size, colour, web, egg sac, range and whether the bite

Crab Spiders

Crab SpidersGoldenrod Crab (Misumena vatia)Identify the goldenrod crab spider (Misumena vatia): size, the red abdominal streaks, how the female changes colour, where it lives and whet

Funnel Weaver Spiders

Funnel Weaver SpidersBarn Funnel Weaver (Tegenaria domestica)Identify the barn funnel weaver (Tegenaria domestica): size, banded legs, its flat funnel web, where it lives indoors, and whether the bite

Nursery Web Spiders

Nursery Web SpidersStriped Fishing (Dolomedes scriptus)Identify the striped fishing spider (Dolomedes scriptus): size, pale side stripes, stream-bank habitat, how it hunts on water and whether itNursery Web SpidersDark Fishing (Dolomedes tenebrosus)Identify the dark fishing spider (Dolomedes tenebrosus): size, chevron markings, where it lives in North America, and whether its bite is da

Jumping Spider

Jumping SpidersBold Jumping (Phidippus audax)Identify the bold jumping spider (Phidippus audax): size, the white triangle, green jaws, how it hunts without a web, and whether its bite i

Living with Alberta's spiders

A few habits cover nearly all of the risk in the province:

• Wear gloves when moving woodpiles, rocks, farm machinery or stored materials in southern Alberta, where widows shelter.
• Clear window wells and check boots and gloves left in an unheated garage.
• Seal gaps around basement windows and doors in late summer, when males wander indoors.
• Vacuum webs rather than spraying; removing the web and the insects that feed it works better than insecticide.
• Leave orb weavers on the porch until the frost takes them; each one eats hundreds of mosquitoes and flies.

For comparison with neighbouring provinces, see British Columbia, where the hobo spider is genuinely common, and Saskatchewan, which shares the prairie fauna almost species for species.