Lady Bugs – Asian Lady Beetles

  • Written by: Killingsworth Environmental
  • February 03, 2011

What Are Asian Lady Beetles?

These beetles were first reported in North Carolina in 1992.

Multicolored Asian lady beetles are about 1/4 inch long. Females are slightly larger than males and specimens from higher elevations are larger than those from the Piedmont and Coastal Plains. These lady beetles vary greatly in appearance. Some have yellowish or orange forewings. Some have beige forewings and some are bright reddish orange.

During the spring and summer, these lady beetles feed on aphids in field crops, gardens, meadows and trees. Multicolored Asian lady beetles are effective predators of aphids and some scale insects and are extremely beneficial for both agricultural and horticultural crops.

As temperatures start to cool in the fall, the adult lady beetles begin their search for protected places in which they can pass the winter. The beetles use visual or physical cues to find suitable overwintering sites. These locations tend to be the sunnier or warmer sides of buildings, or on exposed, light-colored buildings. Of course, this doesn’t mean that people with dark-colored siding, brick or log homes are immune to the lady beetle assault. Recent research suggests that, once the beetles arrive at the site, they use chemical cues to locate the specific crevice they want to inhabit within the structure. The sources of these chemical cues have not been clearly identified, but may be beetle feces from the previous winter, the odor of beetles that died at the site, or an attractant pheromone. These factors may help to explain why beetles seem to pick the same sites (not necessarily every year, but perhaps more frequently than they pick nearby areas).

From the exterior of the house, they may move indoors by crawling under defective weather stripping or by crawling and flying in open doors on warm days. The beetles can fit through very small gaps or cracks in siding, masonry, around window and door casings, and even through attic and soffit vents. The beetles hibernate as adults, usually in wall voids (they cannot survive long in the heated rooms of a house). On warm days, they may become active and move towards light or bright surfaces. The beetles are often found on windows, light fixtures and ceilings. The multicolored Asian lady beetle does not reproduce indoors. In spring, they will move outdoors in search of prey.

Fortunately, multicolored Asian lady beetles are primarily a nuisance only. If squashed, however, the beetles may stain fabric and painted surfaces. They do not eat wood or furniture. Some people have reported receiving a mild “nip” by beetles that have landed on them. There have been concerns that large numbers of beetles may possibly cause air quality problems indoors that could trigger allergies and/or asthmatic reactions.

Pesticides have limited effectiveness in stopping the beetle invasion. While exclusion is not 100% effective, preventing the beetles from entering the home is currently one of the best long-term approaches to dealing with the lady beetles. Check out our pest control services for help!

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