Massive venomous spider builds webs on Ontario porches this time of year

A large venomous spider species is spinning intricate webs across porches, balconies and backyards throughout Ontario this time of year, and while its appearance might give you a heart attack, experts thankfully say there's little cause for concern. 

Neoscona crucifera, more commonly known as the Hentz orbweaver, spotted orbweaver, or barn spider, is a type of orb-weaver spider in the family Araneidae. Although it is venomous, like nearly all spiders, its bite poses no real danger to humans. 

These spiders possess venom capable of paralyzing their insect prey, but their interactions with humans are a little bit less dramatic. According to pest control company Orkin, orbweaver bites "are not considered to be medically important." 

Photo: daniel_bittman/iNaturalist.

The company emphasizes that members of the species "rarely bite, and only do so when threatened and unable to escape," and that the venom's effect is "comparable to that of a bee sting." So, still not the most enjoyable experience.

Over the past few weeks, sightings of the spiders have grown exponentially, with reports from around Ontario uploaded to biodiversity network iNaturalist almost daily. 

Photo: russjones/iNaturalist.

Native to much of North America, Neoscona crucifera is especially visible in the late summer and early fall, when mature spiders begin leaving their large webs up during the day. Earlier in the year, immature spiders take their webs down in the morning and hide in nearby vegetation, making them far less noticeable. 

Females typically grow between 9.5 to 19 millimetres, while males are slightly smaller. You might notice these spiders more as the weather begins to cool, because they'll start taking up residence around your homes, especially near porches, decks, entryways and outdoor lights. 

Although they vary in colour, they can be identified by the alternating dark and light brown bands on their legs, as well as a distinctive black underside marked by two white spots.

Photo: adam1420/iNaturalist.

Artificial lighting helps draw in a steady stream of prey for the spider, including moths, mosquitoes and flies. So instead of actively hunting, orbweavers remain on or near their webs, waiting for insects to get tangled in the silk. 

Although their presence in your outdoor living spaces might feel intrusive, spotted orbweavers are harmless to humans and rarely wander indoors. And while they're primarily nocturnal, they do adapt to a diurnal schedule in the late summer to fall, meaning more sightings are typical and not a cause for concern. 

If you do happen to encounter these spiders, your best bet is to leave them alone and let them be, as they're far more interested in the insects around your property than in you.