Boxelder bug

📖Overview

Boxelder bugs are medium-sized true bugs that feed mainly on seeds and sap of boxelder, maple and related trees. They are most noticeable in late summer and fall when adults and nymphs gather on tree trunks, leaves and sometimes on warm building walls to bask or overwinter. Although they can enter homes in large numbers and leave stains if crushed, they do not bite people, spread disease, or cause significant structural damage.

They overwinter as adults in protected places (bark crevices, rock piles, buildings) and emerge in spring to mate and lay eggs. There is typically one to two generations per year depending on climate. Populations fluctuate with the local availability of host trees and seasonal weather patterns.

🔍How to identify a boxelder bug

Adults are elongated, 9-16 mm long, mostly black with three red or orange longitudinal lines on the pronotum and a red margin on the wings; legs and antennae are black. Nymphs are bright red to orange when young and become darker with age while developing wing pads. When crushed they can release a weak, unpleasant odor.

1. Black, elongated body 9-16 mm long with three red or orange longitudinal stripes on the pronotum
2. Red or orange young nymphs without fully developed wings; adults have red edging on the wings
3. Often found on boxelder or maple trees and in sunny aggregations on warm building walls

Lookalikes

↻Life cycle

1. 🥚

   Egg

   Small, elongated eggs laid in clusters on leaves and twigs in spring; hatch in about 1-2 weeks depending on temperature.

2. 🐞

   Nymph

   Wingless, bright red to orange nymphs that go through several instars, feeding on seeds and sap; gradually darken and develop wing pads.

3. 🐞

   Adult

   Fully winged, black and red adults that reproduce in summer and often aggregate in fall before seeking overwintering sites.

🍃Diet and predators

🌱Effect on plants and gardens

Feed on seeds, sap and developing samaras of boxelder and other maples; damage is usually cosmetic (discolored or shriveled seeds/leaves) and rarely harms mature trees.

How to get rid of boxelder bugs

Prevent entry by sealing cracks around windows, doors, eaves and utility penetrations. Reduce overwintering habitat by removing loose bark, leaf litter and rock piles near foundations. Outside, knock aggregations off walls with a broom into soapy water or collect them with a vacuum. In severe infestations, a perimeter insecticide labeled for exterior use may reduce numbers; follow label instructions or hire a licensed professional. Avoid indoor insecticide use unless necessary.

📍Where and when to find it

Look on boxelder and maple trees, on samaras and seed clusters, on sunny rock faces or building walls, and under bark or in crevices for overwintering adults.

✨Fun facts

• Boxelder bugs are named for their association with boxelder trees (Acer negundo), but they also use other maples and ash trees.
• They commonly gather in large, sunlit groups on warm walls and rocks—this behavior helps them warm up and find mates.
• Despite being called 'scentless plant bugs' (family Rhopalidae), they can produce a faint odor if crushed.

?Frequently asked questions

📷Photos of the boxelder bug