Ladybug infestations occur when these insects seek warm shelter for overwintering, use aggregation pheromones that draw others to the same spot, and find easy entry points combined with favorable environmental conditions.

Overwintering Behavior and Shelter Seeking

In late fall, ladybugs look for a safe, dry place to spend the winter. This behavior is called “overwintering.” They often choose cracks, wall voids, window frames, attics or siding gaps. Once inside, they remain inactive until spring.

Aggregation Pheromones and Chemical Attraction

Ladybugs release special chemicals called aggregation pheromones to signal a good hiding spot. When the first few insects settle, they emit these pheromones and others nearby follow the scent trail. This is why hundreds or even thousands can gather in one building.

Key Factors That Cause an Infestation

• Mild Fall Temperatures – If temperatures stay warm later in the year, ladybugs delay migration and build up in greater numbers before overwintering.
• Easy Entry Points – Gaps around doors, windows, siding seams, and vents allow insects to crawl inside undetected.
• Light and Color Attraction – Brightly colored or light-reflective walls and trim draw ladybugs, as they associate light surfaces with natural rock outcrops.
• Nearby Food Sources – Gardens or landscapes rich in aphids and other plant pests support larger ladybug populations in spring and summer, leading to more insects seeking winter shelter.
• Structural and Environmental Features – South- and west-facing walls warm up first, become prime congregation sites, and may be common on older homes in areas like Nashua, where building gaps are more prevalent.

Understanding and Preventing Infestations

By knowing that ladybugs invade for warmth, follow pheromone trails, and exploit small openings, you can take targeted steps: seal cracks and vents, apply door sweeps, use fine mesh on exterior openings, inspect and repair damaged siding, and reduce outdoor lighting that attracts them. Addressing these causes will dramatically lower the chance of a heavy ladybug infestation.