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Box Elder Bug


Boisea trivittata

Box Elder Bug Facts and Information

Appearance: Box Elder Bugs (Boisea trivittata) are distinct in appearance, usually measuring about 1/2 inch long. They have a black body with red or orange markings on their back. Nymphs are smaller and brighter, mostly red with some black. 

Behavior & Diet: These bugs are primarily plant eaters, with a preference for boxelder trees, as their name suggests. They can also feed on maple and ash trees. They don’t bite or sting and are largely harmless to humans and property, but their large numbers can be a nuisance. In colder months, they tend to invade homes for warmth and shelter. 

Lifecycle: Box Elder Bugs have a simple life cycle: egg, nymph, and adult. In spring, females lay clusters of straw-yellow eggs on leaves and stones. Eggs hatch into nymphs after about two weeks, and they undergo five stages of growth, known as instars, over the summer before reaching adulthood. Adults overwinter in sheltered places, often in homes, and emerge in the spring to lay eggs. They typically have one generation per year. 

FAQs About Box Elder Bug

What are some signs of a Box Elder Bug infestation?

Signs of a Box Elder Bug infestation include: 

  • Large Groups: These bugs are social insects and are often seen in large numbers on trees, especially boxelder trees, and on the sunny side of buildings. 
  • Indoor Sightings: During cooler months, they invade homes for warmth. You might spot them on windows, doors, or in rooms that get a lot of sunlight. 
  • Egg Clusters: Females lay clusters of straw-yellow eggs on leaves and stones. Spotting these can be a sign of their presence. 
  • Excrement Stains: They can leave behind red-orange excrement stains that can discolor curtains, clothing, and other light-colored surfaces. 

If you notice these signs and the infestation is overwhelming, contact Grizz Pest to assist in managing the situation. 

Are Box Elder Bugs harmful to humans or pets?

No, Box Elder Bugs are not harmful to humans or pets. They don’t bite or sting, and they don’t carry any known diseases. However, in large numbers, they can become a nuisance due to their tendency to invade homes during cooler months. Also, their excrement can stain light-colored surfaces. Despite these annoyances, they pose no significant threat to health or safety.

What attracts Box Elder Bugs to homes?

Box Elder Bugs are attracted to homes due to the warmth and shelter they provide, especially during the colder months. These bugs are drawn to sunny sides of buildings where they bask in the warmth. They then enter homes through cracks, gaps in doors, windows, or siding. Once inside, they find hiding places in walls, attics, or other undisturbed areas to overwinter. They are also attracted to their namesake boxelder trees, and homes with these trees nearby may see more infestations.