of Rhode Island GreenShare Factsheets
bugs often invade buildings, especially during the warm days of
autumn, to seek sheltered sites for overwintering. They are attracted
to lights and will readily fly in open doors and windows. Indoors,
these bugs create a nuisance by their presence, produce a foul odor
when crushed, and may stain curtains with fecal matter. Outdoors,
they can be found in large numbers on the sides of trees, buildings
and other structures. Large populations are often correlated with
long, hot, dry summers. During warm winter and spring days, they
may become active, moving from their hiding places into living spaces.
Although they do not cause damage to buildings, clothing, food or
humans, boxelder populations can be a nuisance.
boxelder bugs are flat-backed, elongate, narrow, about 1/2 inch
long, 1/3 inch wide and dark brownish-black with three lengthwise
red stripes on the pronotum (area behind the head). The head
black with the "beak" or proboscis reddish-orange and the long,
thin, four-segmented antennae are half as long as the body. Wings
are thick and leathery at the base and membranous at the tip. There
are red veins in the wings and the abdomen is bright red under
wings. The nymphs, or immatures, resemble the adults in shape except
they are smaller, more rounded, wingless and bright red. Eggs are
During the autumn
months (around October 1), adult and large nymph boxelder bugs
congregate in large numbers, primarily on the bark
of boxelder trees (see diagram below), and then begin migrating
to a place conducive to overwintering. Only full-grown adults
moving to hibernation sites either by crawling or flying. They
may crawl from a nearby tree or fly as many as two miles to
These bugs hide in cracks and crevices in walls, in door and window
casings, around foundations, in stone piles, in tree holes
other protected places. On warm days during winter and early spring,
they sometimes reappear on light-painted surfaces outdoors
south and west sides of the house, resting in the sun. Overwintering
adults leave their hibernating quarters with the coming of
weather (last week of March), and females begin laying eggs (late
April to early May) in crevices of tree bark, stones, leaves,
and on other objects near host plants. Eggs hatch in 11 to 19 days,
with bright-red nymphs appearing about the same time new tree
develop. There are five nymphal instars. The instars become progressively
darker red with each stage. In July, new adults lay eggs that
in a second generation by early autumn. Boxelder bugs feed primarily
on the seed-bearing boxelder trees by sucking sap from the
tender twigs and developing seeds. They have occasionally been
observed feeding on ash, maple, plum, cherry, apple, peach,
grape and strawberries,
causing some scarring or dimpling of fruits. However, boxelder
bugs seldom develop in large enough numbers to become a nuisance,
able to feed on seed-bearing boxelder trees. Apparently, they do
little actual feeding damage to boxelder trees. There may be
to two generations per year.
Since boxelder bugs feed and reproduce primarily on pistillate
(female) boxelder trees, removal of these trees, especially around
the house, would eliminate nuisance populations. Some towns have
outlawed pistillate trees. However, adults are capable of flying
two or more miles for suitable hibernation quarters. If boxelder
trees are desirable for shade, ornamental beauty or other purposes,
use only propagation (cuttings) from the staminate (male) trees.
Eliminate potential hiding places such as piles of boards, rocks,
leaves, grass and other debris close to the house. Rake leaves and
grass away from the foundation in a six- to ten-foot-wide strip,
especially on the south and west sides of the structure. Be sure
to caulk and close openings where boxelder bugs can enter the house,
such as around light fixtures, doors and windows, unscreened vents,
holes in walls and foundations, around utility pipes or conduits,
air conditioners, etc. They are also attracted to lights and can
fly in open doors or windows. Screen all windows, doors, crawl spaces,
exhaust and roof vents and louvers. Clusters of bugs may be killed
by pouring boiling water on them. Be careful to avoid killing grass
and other desirable plants with boiling water.
Should boxelder tree removal be impractical, treat the young, exposed
boxelder bug nymphs on the trees during spring and early summer
to prevent potential large populations and indoor migrations in
the autumn. Insecticidal soap can be used to kill congregrated boxelder
bugs. Treating boxelder tree trunks with residual insecticides can
kill migrating insects.
Acer negundo - Boxelder, Ash-leaved Maple
- Opposite, pinnately compound leaves, 3 to 5 leaflets,
bright green above, lighter green beneath
- Bud 1/4 inch (6 mm) long, greenish or reddish scales
covered with silky hairs
- Stem green to reddish brown, often covered with waxy
whitish bloom that can be rubbed off
- Tree 30 to 50 feet in height, can reach 70 feet
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
of Rhode Island Cooperative Extension provides equal program