Overview
Nuisance pests are the insects — and a few insect relatives — that turn up indoors without biting, stinging, spreading disease, or eating your home’s frame. They are the fast-moving thing in the bathroom, the pincered bug under a flowerpot, the cluster of red-and-black bugs on sunny siding in October. Across Ontario, from Toronto basements to Simcoe County cottages, these species share one habit: they follow moisture and shelter indoors when conditions outside turn against them. A few, like silverfish, do real damage to books and fabrics; most are simply unsettling. What unites them all is that a sighting is usually a signal — of dampness, of a gap in the building envelope, or of other insects for predators to hunt. Getting the identification right is the first step, and this library covers each of Ontario’s eight common nuisance pests in detail.
How to Tell Ontario’s Nuisance Pests Apart
Size, leg count, and shape separate most of these species at a glance. Use the table below, then dig into each dedicated guide for identification photos and control steps.
| Pest | Size | Key feature | Main concern |
|---|---|---|---|
| Silverfish | 12–19 mm | Teardrop body, three tail bristles, silver scales | Damages books, wallpaper, fabrics |
| Earwigs | 12–20 mm | Rear pincers (cerci) | Startling; minor garden damage |
| House centipedes | 25–35 mm | 15 pairs of long striped legs | Harmless predator; signals other prey |
| Millipedes | 25–40 mm | Worm-like, coils when disturbed, 2 leg pairs per segment | Mass migrations after rain |
| Springtails | 1–3 mm | Tiny; jump via a forked tail | Swarm damp areas; snow fleas in winter |
| Stink bugs | 14–17 mm | Shield shape, banded antennae | Odour when crushed; fall invader |
| Boxelder bugs | ~12 mm | Black with three red-orange stripes | Staining; fall clustering |
| Pill bugs & sowbugs | 6–19 mm | 7 leg pairs; pill bugs roll into a ball | Harmless; moisture indicator |
Damage & Health Risks at a Glance
Most nuisance pests are harmless to people and pets — no venom, no disease transmission, no structural feeding. Silverfish are the notable exception for property, grazing on the starches in book bindings, wallpaper paste, and stored clothing. Stink bugs and boxelder bugs create the messiest problems: both release a defensive odour when crushed, and their droppings can stain light siding, curtains, and upholstery. House centipedes, millipedes, springtails, and pill bugs cause no damage at all — their significance is as living moisture meters. If you have a healthy population of any of them, you have a humidity problem worth fixing. For homes and commercial kitchens where zero pest activity is the standard, even a harmless invader is worth acting on.
Seasonal Pattern in Ontario
These pests follow the Ontario calendar closely. Spring melt and wet weather push millipedes and springtails into basements. Early summer — June and July — is peak earwig season, when populations that built up in damp mulch wander indoors, a pattern our June 2026 earwig alert tracked across the GTA. Humid mid-summer brings the moisture-loving crowd, including the centipedes covered in our spiders and centipedes 2026 alert. Fall flips the switch for the overwintering species: stink bugs and boxelder bugs mass on warm, sunny walls in September and October before slipping into wall voids to sleep through winter — Simcoe County saw a record boxelder surge in 2026. Silverfish, indoor breeders, stay active year-round wherever it’s warm and damp.
When to Call a Professional
A few stray nuisance pests rarely need more than a cleanup, a dehumidifier, and some caulk. Call a licensed technician when sightings become regular, when you find damage to books or fabrics, when fall clusters return year after year despite sealing, or when you simply want the whole moisture-and-prey chain handled at once rather than chasing symptoms. Sani IQ uses integrated pest management — inspection, targeted treatment, and prevention — to address the conditions behind a pest, not just the bug you spotted, and backs it with a Pest-Free-Or-It’s-Free guarantee. Explore residential pest control, check plans and pricing, or request a quote.
References
- Health Canada — Silverfish and Firebrats
- Health Canada — Earwigs
- University of Minnesota Extension — Sowbugs, Millipedes and Centipedes
- Ontario.ca — Brown Marmorated Stink Bug
Last updated: July 16, 2026 · Reviewed by Sani IQ licensed technicians