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What Time is it in Nature: Boxelder Bug

March 14, 2014

Thanks to the warm weather we’ve had recently, we’ve started to see the first insects emerging at Prairie Ridge!  Several species have been spotted on the grounds over the past week.  One insect species is already forming large groups, the Eastern Boxelder Bug (Boisea trivittata).

Boxelder Bug

Eastern Boxelder Bugs are a part of the insect family Rhopalidae, the scentless plant bugs.  The adults are just under a half-inch long and are slightly flattened on top.  They are dark brown or black with vivid red-orange markings: three lines down the thorax (their species name, trivittata, refers to these lines), a line down either side, and diagonal lines across the wings.  The nymphs, or immature stages, are smaller and mostly red, but they also lack the wings of the adults.  This species is common throughout the eastern two-thirds of the U.S. and reaches north into Canada and as far south as Guatemala.

Boxelder Bugs overwinter as adults and emerge in the spring.  Once they do, they often form large aggregations, groups of bugs that remain in close proximity to one another.  They aggregate in part for protection from predators and gain safety in numbers, but it also makes finding a mate relatively easy.  Spring aggregations, like we’ve started to see at Prairie Ridge, are typically found in warm, sunny spots on south-facing trees, slopes, rocks, or walls near Boxelders or other host plants.  You may see several hundred bugs at a time, warming themselves in the sun.

Boxelder Bugs feed on primarily Boxelder trees (Acer negundo), though they will also feed on other Acer species (maples), soapberries, and the occasional ash.  They prefer feeding on the seeds, but will also eat the leaves when there are no seeds available.  In spite of their feeding habits, Boxelder Bugs rarely become so numerous that they damage trees.  They are not considered forest or agricultural pests, though the best female Boxelder trees (the seed producers) can attract shocking numbers of bugs.

In addition to feeding on Boxelders, Boxelder Bugs also rely on the trees for reproduction.  Adults will gather near Boxelders and other host plants in the spring and mate.  Females will then lay their small yellow eggs in the crevices of the bark when the first vegetation begins to appear.  The eggs hatch in 10-14 days and the nymphs feed on the leaves and seeds of the host plant.  They will molt four times before becoming adults, typically in late spring or summer.  If the weather is particularly good, these bugs may produce a second generation the same year.

In the fall, Boxelder bugs form aggregations in warm, protected places.  Human homes are lovely warm places, so they are known to invade in winter, squeezing in through cracks and other openings.  The bugs cause virtually no damage to the home’s structure, contents, or occupants, so they are considered a nuisance pest rather than a destructive pest, but many people find their presence indoors distasteful.  You can prevent the bugs entering your home by making sure that windows, spaces around pipes, and other possible access points are well sealed.  If they do end up in your home, it’s easy to remove them by sucking them up with a vacuum cleaner, though you must also determine where they are getting in and seal it if you don’t want to find more.

We’ve spotted Boxelder Bugs aggregating along the Forest Trail between the trailer and the Nature PlaySpace.  Next time you visit Prairie Ridge, be sure to look around in the dried leaves to either side of the trail!  If you see large numbers of half-inch brown or black bugs with red markings, you are looking at the adult Boxelder Bugs that made it through the winter and are now eager to reproduce.  You might even see pairs, attached back to back, wandering around the forest floor together – a sure sign of reproduction.  Aggregations like these are a great sign of spring, so hopefully more warm weather is just around the corner!

What Time is it in Nature is a weekly feature highlighting the current plants, animals, and other wildlife at the Musuem’s public outdoor facility, Prairie Ridge Ecostation.  Find out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive!

(Photo by Chris Goforth)

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