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Pest Management Priducts Division of CSPA
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The adult Boxelder bug is about ½ inch in length and brownish-black in color with three red stripes on the thorax and several fine red lines on the wing margins. The abdomen is also bright red. The wings lie flat on the back when at rest.
Boxelder bugs usually feed on the leaves, flowers, and seedpods of the female or seedbearing boxelder tree (Acer negundo). They may also occur on male boxelder trees and occasionally occur on maple and ash trees. Boxelder bugs can feed on the fruits of almond, apple, cherry, peach, pear, and plum trees, and on grapes, where their feeding punctures can cause the fruit to become deformed. Large numbers usually occur only on seed-bearing female boxelder trees.
Boxelder bugs pass the winter in the adult stage in dry, sheltered places where they accumulate in large numbers. They often choose buildings or houses as a protected place to over winter. When the weather warms up in the spring, these insects leave their places of hibernation to fly to boxelder trees where they lay their eggs (which typically hatch in 10-14 days) in crevices of tree bark or on leaves, grasses and on other objects near host plants. Eggs are yellow when first laid and become a rusty red color as the nymphs develop inside. The young nymphs are bright red with the head end tending to be darker. When the nymphs are about half-grown they become marked with black and begin to develop black wing pads. Nymphs feed in the same way as adults by inserting their proboscis (mouthparts) into leaves, fruits or soft seeds and sucking out the plant juices. Feeding continues throughout the summer and the nymphs gradually mature becoming adults as cold weather approaches in the fall. There are 5 nymphal instars or stages before the adult appears. In some areas there may be two generations per year, one reaching maturity in mid-summer and the second one in early fall. Most of the nymphs of the second generation mature to adults by fall where they look for dry sheltered places to over winter such as hollow tree trunks or in cracks and crevices in walls.