INTRODUCTION
The common name reflects the fact that this species is a major pest of boxelder trees, Acer negundo Linnaeus. Boxelder bugs are primarily a nuisance pest because they enter structures to overwinter. This species is native to the western states. It is now found from eastern Canada , throughout the eastern United States , and west to eastern Nevada wherever boxelder trees are found.

RECOGNITION
Adults about 1/2 “ (11-14 mm) long; elongate-oval, somewhat flattened with head narrower than pronotum. Color black with reddish lines on dorsum, pronotum with margins and median line reddish, and basal half of wings with reddish margin. Head with ocelli present; mouthparts piercing-sucking, forming a beak held beneath body when not in use. Antenna 4-segmented, about half body length. Wings with outer membraneous  (like cellophane) part many veined. Scent glands (opening on each side of thorax between 2^nd and 3^rd pair of legs) absent.

Nymphs similar to adults but lack wings although wingpads may be present, and bright red in color.

SIMILAR GROUPS
(1) Western boxelder bug (Boisea rubrolineata) shorter, averaging 3/8” (10 mm) long, basal half of wing with red margin and 3 longitudinal red stripes, and found in Nevada, Arizona, Texas, the Pacific Coastal states, and British Columbia. (2) Small milkweed bug (Lygaeus kalmii) with pronotum lacking median red line, head with red mark between eyes, and membraneous tip of wings with only 4 or 5 veins. (3) red bugs or stainers (Pyrrhocoridae) lack ocelli and front femora usually enlarged/swollen. (4) Leaffooted bugs (Coreidae) with well-developed scent glands and hind tibiae often expanded and leaflike. (5) Seed bugs (Lygaeidae) have membraneous part of wings with only 4 to 5 veins and front femora usually enlarged/swollen.

BIOLOGY
The overwintering adults emerge from hibernation and the females lay clusters of straw-yellow eggs on stones, leaves, grass, shrubs, and trees, especially in the bark crevices of boxelder trees. These eggs turn red as the embryos develop and hatch in about 2 weeks. These nymphs feed on fallen boxelder seeds and later on new leaves, going through 5 instars. In the warmer regions of the United States , there are 2 generations per year.

HABITS
The overwintering adults emerge from hibernation when the boxelder buds open and fly back to their host trees, typically in late April to early May. They first feed on the fallen boxelder seeds and later move to the female boxelder trees when the seeds begin to form, feeding on the newly developing leaves.

The primary host plant is the see-bearing (female) boxelder tree, but they also occur on seed-bearing silver maple trees, Acer saccharinum Linnaeus. They do not feed on the male trees. Occasionally, they will feed on the fruits of plum and apple trees.

In the autumn, boxelder bugs become gregarious and congregate on the south side of rocks, trees, and buildings where the sun hits. After large masses congregate, they may fly to nearby buildings to hibernate for the winter.

Inside, boxelder bugs are primarily a nuisance pest. However, their fecal material may cause a red stain, resulting in discoloration on curtains, drapes, clothing, and other resting places. When crushed or handled roughly, they produce a strong, disagreeable odor. They occasionally “bite” people, causing as skin irritation and producing a red spot similar to a small ulcer.

CONTROL
No attempt should be made to kill these bugs in wall voids at any time because dead insect bodies attract dermestid beetles (larder beetles, carpet beetles, etc.). Dermestid larvae wander and readily enter the living space, causing numerous complaints. Instead, wait until summer when all live overwintering adults are out of the wall voids. Then follow the outside control measures given below. However, temporary relief is possible by using a vacuum to remove the bugs and sealing their entryways into the living space.

Control begins outside. Reducing the outdoor population of boxelder bugs is highly recommended. Reduction is achieved by spraying infested trees with the application timed to kill the young 1^st generation nymphs and then again for those of each succeeding generation. Such spraying requires special equipment and usually an ornamental license, so it is typically done by a private contractor.

Unfortunately, on occasion some or all of the infested trees may not be on your customer’s property. In this case, the neighbors should be educated about the problem in an attempt to secure their cooperation. Regardless, use of preventative physical and chemical barriers aimed at adults before they congregate and attempt to enter buildings is recommended. Physical barriers involve exclusion. Although total exclusion is probably not possible, all vents (roof, overhang, weepholes, etc.) should be screened with at least 16-mesh screening. Caulk (silicone based is recommended) around cable entrances, windows, doors, overhangs, facia boards, etc. Installation of closable chimney caps may be advisable. These steps should be taken in June or July.