of Rhode Island GreenShare Factsheets
Centipedes, Sowbugs & Pillbugs
Occasionally millipedes, sowbugs, pillbugs and centipedes
may be found in moist areas of the home, in rotting wood or under
piles of moist debris in basements, near patio doors and in garages.
None of them are true insects, but they belong to the class Crustacea,
a closely related group of arthropods. Centipedes, sowbugs, pillbugs
and millipedes are all primarily nocturnal, avoiding light. They
are fairly common out-of-doors and may be seen near foundation
walls, under logs, in piles of leaves and in gardens. Occasionally
large numbers of millipedes leave the soil and crawl onto and
into (if there are openings through which they can enter) houses
where they may be an extreme nuisance to home dwellers. In a
few instances invasions have been noted after periods of extremely
wet weather and persist for a few weeks or until cold weather
Millipedes ("thousand leggers")
have elongated, segmented worm-like bodies with short antennae
and two pairs of short legs
per body segment. There are many species of millipedes, but the
ones that commonly invade homes are usually 12-40 mm (1/2 to
1-1/2 inch) long, brown or black, and curl up when disturbed.
They crawl slowly across the ground and, when disturbed, roll
themselves into a coil. A few species which occur in wooded areas,
however, may exceed 10 cm (4 inches) in length. Millipedes deposit
eggs in clusters in the soil throughout the summer. Young hatch
from the eggs and undergo a series of molts, during which the
number of segments is increased. It often takes more than one
year to reach sexual maturity. Occasionally millipedes will attack
the stems and roots of young plants, or they may feed on tubers
or vegetables stored in cellars or basements. Such damage, however,
most frequently occurs in the presence of previous damage, as
millipedes customarily feed on decaying vegetation.
Sowbugs and pillbugs are oval, dark-gray, hard shelled
arthropods with seven pairs of legs. They reach about 12 mm (1/2
inch) in length. They are also found in moist places, under debris
or in damp soil where decaying vegetation provides food and,
like millipedes, they can cause some damage to young plants.
When disturbed, pillbugs can roll themselves into a ball, but
sowbugs cannot. The females of sowbugs and pillbugs carry the
young in a pouch on the underside of her body until the young
leave the pouch. They may have two or more broods per year. Sowbugs
often live to be two years old.
Centipedes ("hundred-leggers") are
elongated, short-legged, flattened arthropods with 15 or more
pairs of legs. Centipedes
are gray to light brown and about 25-50 mm (1-2 inches) in length.
There is one long pair of legs per body segment and the antennae
are prominent. When disturbed, centipedes often run for cover,
moving much more rapidly than millipedes. Centipedes can deliver
a somewhat painful, venomous bite and should be handled with
appropriate care. These arthropods are not likely to infest houses
unless conditions are quite moist and prey is abundant. Centipedes
are predaceous, feeding on insects, spiders and other small animals.
They do not cause damage to plants.
The heaviest migrations usually come from nearby wooded
areas. Removing piles of rocks, boards, leaves, compost, and
general refuse from around buildings will help reduce millipede,
sowbug, and pillbug numbers. To keep these pests out of the home,
foundation walls should be repaired, and any cracks around doors,
basement windows or similar openings should be sealed with caulking
compound. Correcting the conditions that might lead to excess
moisture indoors is the most effective long-term solution. A
good first step towards controlling the household centipede is
to eliminate the presence of insects or spiders on which they
may be feeding.
Some species of millipedes, sowbugs, and pillbugs are difficult
to kill with any insecticide. Select only formulations of these
insecticides labeled for millipede, sowbug and pillbug control
and follow label directions closely. Apply the spray to any infested
area outdoors and as a barrier treatment on foundation walls
and soil adjacent to the buildings. Use enough to thoroughly
wet the surface being treated and any visible millipedes, sowbugs
or pillbugs. Repeat applications may be needed if these creatures
continue to move in from surrounding areas.
Any millipedes, sowbugs or pillbugs
that are found indoors can be eliminated by hand collection,
vacuuming or otherwise
sweeping them up. Centipedes may be killed by squashing with
a gloved hand (remember, they can bite) or any makeshift "swatter."
Adapted from the Cornell
Cooperative Extension and the Purdue University Cooperative Extension
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