Length: to ½ inch
Boxelder bugs are harmless black insects with flattened backs and distinctive red markings. You may find them swarming on the warm, south-facing side of your home this time of year as they seek shelter for the winter. They go dormant as the weather gets colder, but if they are warmed by your home’s heating, they may revive, mistaking the warmth for springtime.
Boxelder bugs go through several immature stages before becoming winged, mature adults. In autumn, large nymphs and adults gather in the nooks of box elder bark, under the siding of homes, and similar places to prepare for overwintering. At the end of March, they emerge and begin laying eggs at the end of April in crevices of box elder tree bark.
Their preferred food is box elder (Acer negundo), though they are sometimes found on other maples, especially silver maples, and ash trees. Generally, they feed on the soft, leafy parts of trees. Boxelder bugs have strawlike mouthparts, similar to cicadas, for sucking juices from the tender leaves and seeds of their host trees. Despite their feeding habits, boxelder bugs rarely damage trees.
Boxelder bugs have red markings that form an X, almost as a warning to predators that they are distasteful. Many predators, such as praying mantises and spiders, eat them anyway.
Boxelder bugs live on or near their favorite food source — box elder trees — but don’t be alarmed. You may see high numbers of these bugs in the fall, but they pose no danger to humans, pets, or buildings.
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