| Feature | Asian lady beetle (H. axyridis) | Two-spotted ladybug (A. bipunctata) | Seven-spotted ladybug (C. septempunctata) |
|---|---|---|---|
| Colour variation | Highly variable — pale orange to deep red | Red or orange, stable | Bright red, stable |
| Spot count | 0–22 spots (variable) | 2 black spots | 7 black spots |
| Pronotum marking | White M or W shape on black pronotum | Dark, no distinctive mark | Black with white sides |
| Size | 6–8 mm | 4–5 mm | 7–8 mm |
| Overwintering in homes | Yes — forms large aggregations | No — overwinters in leaf litter outdoors | No — garden leaf litter |
| Bite humans | Yes, mildly | Rarely | Rarely |
| Defensive fluid | Yes, yellow, strong odour | Minimal | Minimal |
Why Asian lady beetles enter BC homes
Harmonia axyridis is native to Asia where it overwintered in cliff faces and rock outcroppings. In BC, buildings serve as the structural equivalent — particularly south- and west-facing walls that heat up in October sun. The species aggregates using chemical signals (pheromones) that persist in buildings and attract returning and new individuals year after year. In Metro Vancouver, Asian lady beetle aggregations are most common in agricultural areas adjacent to fruit orchards and hop yards where the species was deliberately introduced as a biocontrol agent for aphids. Surrey, Langley, Abbotsford, and Delta see more pressure than urban Vancouver. But populations have spread throughout the Lower Mainland and suburban homes anywhere near gardens can experience autumn aggregations. The scale varies dramatically — from a few dozen individuals on a south wall to tens of thousands clustering in an attic. The larger events are associated with warm, dry October days when large populations are simultaneously seeking overwintering sites.
Asian lady beetle exclusion and management protocol
Exclusion before October is the primary approach. Pesticide use inside the home is not recommended — dead beetles are more difficult to manage than live ones.
- 1Seal entry points before OctoberInspect and seal window and door frame perimeters, soffit-fascia junctions, utility penetrations, and any gap in exterior cladding. Asian lady beetles enter through gaps as small as 3 mm. Caulk all gaps with exterior-grade flexible caulk. Install door sweeps if not present.
- 2Attic and roofline exclusionReplace torn window screens and attic vent screens with 0.6 mm mesh. Asian lady beetles can enter through standard window screen mesh (the holes are usually slightly too large). Install fine-mesh overlays if needed on existing screens.
- 3Exterior residual treatment — SeptemberA pyrethroid residual application (lambda-cyhalothrin, bifenthrin) on south and west-facing exterior walls in September reduces the number aggregating and entering. Reapply if rain washes it off before the main migration in October.
- 4For beetles that enter: vacuum, do not sprayVacuum aggregations of beetles inside the home using a vacuum with a collection bag. Do not spray beetles indoors — dead beetles in wall voids attract larder beetles and carpet beetles that then damage fabrics and stored food. Vacuum contents should be emptied outdoors immediately.