Nine-Minute Naturalist: Home Invasion

By David,

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Home Invasion

by Josh Palumbo, Forest Management Coordinator

I welcome you to The Nature Foundation at Wintergreen’s attempt to bring some nature and knowledge into your home. The Nine Minute Naturalist borrows from NPR’s lovely 90-Second Naturalist podcast. Since we all have a bit more time on our hands, the goal is to take something that is happening out in our environment and stimulate your brain for roughly nine minutes. I hope you enjoy!

I pride myself on using the Nine Minute Naturalist as a tool to prepare readers for many of the unique attributes our environment has to offer. I had a great opportunity to ready our community for an epic invasion this fall and failed miserably. Each fall homes across Wintergreen suffer from an invasion and I sat back silently. That silence ends now. This Nine Minute Naturalist will help prepare you for future invasions of the ever-annoying Asian lady beetle.

Multicolored Asian Lady Beetle (MALB) belong to the family of beetles known as ladybugs. Adult MALB have the traditional oval shape consistent with other ladybugs and come in a variety of color combinations. North American populations have a mix ranging in color from pale yellow-orange to bright red-orange. Some will have black spots on their wing covers while others will not. They can be distinguished from other ladybugs by their distinct “M” on the pronotum (the area between the head and thorax).


Multicolored Asian Lady Beetle


These beetles where first introduced into California in 1916 to control crop damaging aphids. For this job, the MALB was well chosen. As adults, they can eat 90-270 aphids per day and as larva, they can eat up to 1200 aphids during development. Their massive population growth can be attributed to abundant prey and lack of native enemies to act as controls. They were not identified as a pest until 1988 when an infestation site in Louisiana revealed the multicolored Asian lady beetle as a potential nuisance across North America.

To properly understand a nuisance species, knowledge of the life cycle is crucial. MALB has four distinct life stages: egg, larva, pupa, adult. Beetles overwinter as adults and emerge in the spring to lay 600-800 eggs on the underside of leaves. The eggs hatch in 3-5 days. The larval stage lasts 12-14 days while the pupal stage lasts 5-6 days. Once they reach adult stage, they can live 2-3 years in optimal conditions. This life cycle takes approximately one month allowing for many generations each year. This leads to a very rapid population explosion when food sources allow.

Each fall prompted by daylength and temperatures, the MALB leaves feeding sites and seeks overwintering locations. This usually occurs in mid to late October at Wintergreen. The migration flights are heaviest on warm, sunny days following a period of cold weather. Most flights will occur in the afternoon around peak temperatures. The Asian lady beetles are attracted to illuminated or light-colored exterior surfaces such as a garage door facing afternoon sun. Dwellings located near woods and fields are especially prone to infestation, which describes almost all of Wintergreen. Once they land on a site, they seek crevices and protected spaces to spend the winter. This typically includes cracks around windows and door frames, behind exterior siding, attics, or any other spot they can enter and be protected from the elements. The process reverses in late winter/early spring.  As temperatures warm, the beetles become active and seek to escape outside. Many will inadvertently wander into the house and are usually found in numbers near light sources such as windows or light fixtures.



The positive aspect to thousands of insects invading your home is that they do not harm humans. They do not reproduce in your house nor attack food, wood, or clothing. They do emit a bit of an odor and have been found to secrete a staining substance when disturbed. Essentially, they fall under the category of nuisance that can be mitigated. The first course of action is to ensure by mid-fall every year you have sealed entry points. Screening and fine quality latex caulk are your best bets when sealing holes that the beetles can enter through. Pesticides can be applied to the outside of the house from late September or early October to provide a chemical barrier if you are particularly averse to this pest. Once inside your home, a vacuum or broom are your best bets to combat the voluminous intruders. It is not recommended to use bug “bombs” or spray insecticides inside your home to combat this pest.

Home invasions are never desired but this version is easy to deal with. Use the lovely sunny fall weather as a reminder each year to analyze the “chinks in the armor” of the exterior of your house. Find the gaps, cracks, and holes this beetle will seek out and make your home safe from the invasion.

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