Box Elder Bug (Boisea trivittatus)
Adult Box Elder Bug
Credit: Terry Thormin
Part of an aggregation of Box Elder Bugs showing both adults and
immatures. The adults are darker and have wings
Photo CD 0023 3291 1601, Image #41 - Credit: John Acorn
Although the official name for this insect is the Box Elder Bug,
most Albertans call it the Maple Bug. The reason: it feeds on the Box
Elder Tree, but in Western Canada this tree is known as the Manitoba Maple.
This is a medium-sized (11 - 14 mm) bug that is black with red markings.
Unfortunately this describes a lot of different insects. The photograph
will help eliminate most other bugs, but keep in mind this photo shows
both adults and immatures; the immatures are smaller and redder and lack
wings. This is a true bug, with piercing, sucking mouthparts.
The Box Elder Bug is restricted to the prairies in Alberta. It is widely
distributed in North America east of the Rockies from southern Canada south.
TIME OF YEAR
Although the young can be found by mid-summer, the adults usually appear
by late summer and can survive until quite late in the fall.
HABITAT AND HABITS
The Box Elder Bug feeds extensively on Manitoba Maple or Box Elder,
sucking up the sap and weakening the tree. This may result in leaf
mottling and premature leaf drop. This insect overwinters as an adult
and tends to congregate in large numbers for this purpose. At times
it can be numerous on sunnier walls of houses and can become a nuisance
if individuals find a way into the house.
Where they occur, the Large Milkweed Bug (Oncopeltus fasciatus)
and Smaller Milkweed Bug (Lygaeus kalmii) could easily be confused
with the Box Elder Bug. They have more extensive red or orange markings
on them and feed exclusively on various species of milkweed. They also
never congregate in large numbers in the fall.
When present in large enough numbers Box Elder Bugs can do damage
to Manitoba Maple trees. Most people call us in the fall because
they are curious about the large numbers on the walls of their
houses or concerned about the numbers that are getting in the
houses. Washing them off the walls of the house with a blast
of cold water from a hose may help. The only way to ensure that
they do not get inside the house is to fill in all cracks where
they could be getting in, a rather daunting and expensive task.
For more information on controlling Box Elder Bugs when they
reach pest numbers, please go to the following website
We cannot provide advice on controlling insect pests. If you need more
information beyond what has been provided here, we suggest you either search
further on the web, or talk to a local exterminator.