By Judy Sedbrook, Colorado Master GardenerSM, Colorado State University Cooperative Extension, Denver County
The adult boxelder bug, Leptocorouos trivittatis, is 1/2" in length. Its black and red cross pattern on the back makes this insect easy to distinguish. The boxelder bug sucks the sap from leaves and flowers of its host plants but doesn't cause much damage.
Lifestages of the Boxelder Bug
Most years the number of boxelder bugs found in and around the yard is insignificant. If winters have been mild, large populations may build up and may become a nuisance. The bugs can be found in large groups on the sunny side of tree trunks, fences, garages and houses. They are most numerous in areas where boxelder trees grow.
They normally survive the winter by crawling into cracks and holes in bark but also swarm into houses or crawl under siding or cracks in concrete, window and doorsills. They produce no odor nor do they bite. They are harmless and cause no damage other than occasional spotting of windows and draperies.
For more information on boxelder bugs, see CSU Fact Sheet 5.522.
Photographs courtesy of Judy Sedbrook and Kansas State University
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010