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Pillbugs and Sowbugs

Two of the most well known “bugs” in Colorado is not really insects at all.  Pillbugs and sowbugs are actually land living crustaceans called isopods.  Both pillbugs and sowbugs breathe through gills on their abdomens; have plated bodies, two pairs of antennae and seven pairs of legs.  There are a few important distinguishing features between pillbugs and sowbugs.  The most notable characteristic is that pillbugs can rapidly roll into a ball when disturbed or threatened, hints their nickname of a roly-poly.  Sowbugs plates tend to flange outwards at the edges creating a more armored look.  They also have tail-like appendages that protrude from their hind end.

Originally from Europe, pillbugs and sowbugs are now widely distributed and common in and around homes in Colorado.  They feed on plant matter, especially when softened by decay.  Weak mouthparts for chewing limit their damage to healthy plant tissue.  Active primarily at night, pillbugs and sowbugs can be most often found during the day resting under rocks, landscaping pavers and other moisture retaining materials.  They are also commonly active during the day following rain showers or during overcast conditions in which they are less likely to experience excessive drying from the sun.   Sowbugs and pillbugs are slow growing, reaching adulthood at about one year of age.  Adults commonly live 2 or more years.  Both pillbug and sowbug females have a special pouch called a marsupium in which eggs and freshly hatched young are contained within the mother for a period of several months until they are ready to live on their own.  Young then go through a series of molts over a period of time, but always resemble the adults with the exception of their size.  A majority of the mortality rate of young pillbugs and sowbugs is a result of extreme drying.

Pillbugs and sowbugs found indoors are accidental invaders and are likely to be found in moist areas.  They can also be found in potted plants that are moved from the exterior to the interior of the home.  Sowbugs and pillbugs pose very little to no threat within the home and are considered more of a nuisance pest by residents.  Exterior pesticide applications aide in controlling pillbugs and sowbugs by creating a barrier around the perimeter of the home while interior applications will resolve current indoor occurrances.  Reduction of moisture both interior and exterior will reduce pillbug and sowbug activity as well.