Clusterflies, Ladybugs and Boxelder Bugs, Oh My!

A very cold, but sunny, day in February in the Midwest can bring out some very unnerving and uninvited guests. No, your home is not possessed (as in The Amityville Horror). Those clusterflies, or ladybugs, or boxelder bugs have been in your home since fall and the warm sun on their hiding place has convinced them it’s spring so they have become active. These 3 insects over-winter as adults and can become persistent pests if present in large numbers.

The clusterfly lays its eggs in the soil where the larvae become parasites in earthworms. After pupating the adults feed on pollen until late summer when they gather in large numbers as they look for places to over-winter. While hollow trees and loose bark were natures harborage houses are even better. The flies find gaps in siding, roofing, or joints and enter walls, soffits or attics where they stay, inactive, until spring. Unfortunately, weather conditions often confuse the cycle and the insects become active when it is too cold to go outside. These insects often are drawn by the light into the house where they fly around until they die. There is no food source, they feed on pollen.

The Asian ladybug was introduced to North America to sell to farmers and homeowners as a natural control for aphids. While they are voracious they also can bite, feed on many other insects and over-winter in huge masses in the walls, soffits and attics of homes. Like clusterflies they also can become active during winter and become a nuisance in homes.

Boxelder bugs happily spend the summer reproducing and chewing on boxelder trees. In late summer they gather in leaf litter around homes and can be seen crawling on the sides of houses. Once in they are also inactive until spring unless prematurely awoken. If inside the home they die after several days due to a lack of food and low moisture.

Daily vacuuming of live and dead insects is recommended. Light traps in attics may reduce the numbers that get into the house itself as these insects are all attracted to light. Spraying with a residual or contact insecticide is not recommended as once these insects are active and inside they are going to die whether you spray or not. Since they fly you would have to fill the rooms with aerosol and spray walls and ceilings making a real mess.

Caulking, sealing and screening helps but all of these insects can enter through tiny gaps so you’ll never seal them all out. Thoroughly treating the outside of the building from gutters to ground in late summer to early fall can greatly reduce the numbers that get in. Timing is crucial.