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Occasional Invaders & Nuisance Beetles

General Facts

While they rarely, if ever, prove to be destructive or harmful, certain species of beetles in Canada occasionally invade homes and other structures. Primarily outdoor dwellers, these occasional invaders enter buildings to seek shelter from changing weather conditions or to look for new sources of food. Typically more of a nuisance than a health or safety threat, occasional invaders such as lady beetles and ground beetles often congregate in large numbers when they move indoors, thereby becoming a pest to the occupants of the structure.

Types of Nuisance Beetles in Canada

Ground beetles alone comprise over 900 different species that live throughout Canada. Generally speaking, most adults of the Carabidae family move rapidly and look similar, with flattened bodies that appear greater in length than width. Ground beetles are identifiable by the striations that occur on the wing covers of nearly every species. The flying skills of the insects vary by species; most are strong flyers, while others are less-skilled or reluctant to take flight. In addition to ground beetles, other types of nuisance beetles found in the Canadian provinces include various species of lady beetles, such as the Asian lady beetle.

Appearance / Identification

Red or orange in colour and oval in shape, the Asian lady beetle is known for the telltale black spots found on the carapace of the body. The arrangement of spots varies in both size and pattern from beetle to beetle, while the head typically appears white in colour and is usually concealed under the pronotum, resulting in an appearance that resembles the letter “M”. As adults, Asian lady beetles measure around 7 mm in length and nearly 6 mm in width.

Conversely, ground beetles range in size from 3 to 12 mm. Most species display a shiny black or green colouration. The insects also typically boast prominent mandibles, with a narrow head and longer legs than other species of beetles.

Habitat

Found in various types of environments, nuisance ground beetles commonly live in forests, meadows, agricultural fields, and along the shoreline. The Asian lady beetle was introduced in Canada to help control invasive pests and reside among the deciduous trees and other flowering plants in a given region.

Diet

Most species of occasional invaders and nuisance beetles species are beneficial to humans and eat other, more destructive insects in the environment. The majority of ground beetles, for instance, are advantageous predators that feed on anything smaller than themselves. Other types of nuisance beetles prey on caterpillars and slugs, while some may even consume small vertebrates as well as arthropods and arachnids. Lady beetles feed on aphids, mites, and even other lady bugs. Some will also eat pollen and certain fruits.

Life Cycle / Reproduction

Like most other insects, nuisance species of beetles go through a multiphase life cycle, as the pests hatch from eggs and develop from larvae to pupae before finally emerging as fully mature adults. The Asian lady beetle, for example, breeds multiple times throughout its life and lays eggs in clusters. When the larvae hatch, they feed on unfertilized eggs nearby, especially in the absence of another food source. Adults lady beetles may live up to 90 days.

Most ground beetles lay their eggs under the surface of the soil, which allows the larvae to overwinter in a protected location after hatching. Ground beetle larvae pupate while overwintering and emerge as adults the following spring.

Problems Caused by Nuisance Beetles

Not particularly destructive, nuisance beetles can nevertheless cause alarm or frustration when they invade homes in large numbers to seek food or refuge from the weather. The Asian lady beetle is an aggressive species and is displacing and suppressing many native lady beetle species. Furthermore, ground beetles that feed on grapes may cause the fruit to develop a bad taste stemming from the secretion of chemicals that ward off predators. Similarly, certain species of ground beetles sometimes feed on corn, which could detrimentally affect crops if a large enough population is present.

Detection / Signs of Infestation

The most common sign of infestation is the sight of the beetles assembling in or near a structure. Ground beetles do not typically swarm. However, they are attracted to lights and heat, making commercial buildings just as susceptible to infestation as homes. Lady beetles do swarm, sometimes in the thousands, when they look for suitable overwintering sites. Occasional invaders are often found along windowsills or near other openings leading into the home. The pests also gravitate towards moist, damp areas, such as basements and other common storage spaces.

Prevention Tips

Like most home-invading insects, nuisance beetles typically enter structures through weakened areas or cracks in the building foundation. To keep the pests out, repair screens and block any access points that could be susceptible to an infestation. Additionally, seal cracks in the foundation and open gaps around wires and plumbing with caulk. Use weather-stripping where appropriate, and change bright, white outdoor light bulbs to dull, yellow bulbs to reduce the number of beetles being attracted to the property.

Control / Removal

While most occasionally invading beetles do not harm people or pets, their presence causes discomfort for people who are unwilling to share their homes with the pest insects. Upon invading, most ground beetles die from lack of food, and none of the species found in Canada breed indoors. For species that amass in larger numbers, however, unassisted removal may prove to be difficult. Contact a trained pest control professional to ensure the effective removal of a nuisance beetle infestation.