Swarms of red and black bugs are taking over Ontario homes right now

It's officially that time of year again when you might notice swarms of red and black bugs congregating around your property, and there's a good reason why.

While native to North America, boxelder bugs (Boisea trivittata) are seasonal nuisance pests that become particularly pesky in the fall as they leave the trees where they live and feed to search for warm hiding spots in preparation for winter.

During their intense search, the pests gather in the sunshine on the south sides of buildings, trees, and rocks, and from there, stray into your home through small cracks in the foundation, gaps along doors and windows, and open vents. During the winter, they're also known to gather inside sheds, in wood piles, and around window casements.

As fall quickly approaches, dozens of sightings in Ontario have already been uploaded to the social network biodiversity app, iNaturalist, including in cities like Hamilton, London, Cambridge, Peterborough, Guelph, and Toronto.

Boxelder bug sighting reported in Erin, Ont. Photo: lorysa/iNaturalist.

Throughout the summer, the seasonal pests feed on the seeds of boxelder trees (which happens to be where they got their name from), as well as maple and ash trees. The bugs can be identified by their almond-shaped bodies, which are black with red edges and can grow up to 14 mm long.

Their striking colours and large presence might make them seem intimidating, but boxelder bugs are not known to bite humans and do not cause structural damage to homes. While certainly annoying, the bugs also inflict minor cosmetic damage to trees, leaving behind slightly discoloured leaves or fruit distortion.

If you want to keep the nuisance pests away from your property, make sure to repair any small openings in damaged window or door screens, and seal up any exterior cracks or gaps around your doors, siding, windows, and areas where utility pipes enter your home.

Sighting reported in Hamilton, Ont. Photo: glennbarrett/iNaturalist.

The last thing you'll want to do is squish boxelder bugs if you do come across them, as their guts emit a foul odour that can leave permanent red stains and attract other bugs like carpet beetles.

Other preventative methods include removing any leaves, rocks, and boards around your home, and this will discourage the pests from gathering in large clusters. If you do come across any of these bugs inside your home, your best bet is to vacuum them or gently sweep them outdoors.