You don’t mention the size of the insect.  If a half inch or slightly less, they may be a Raglius species.  Large masses of them often appear in irrigated gardens during fall.  Any that come indoors are considered a nuisance.  Pesticides won’t help; instead, capture and release outdoors or vacuum them up.  See this info from the University of Idaho about the “Tuxedo Bug.”  http://www.cals.uidaho.edu/edcomm/pdf/CIS/CIS1147.pdf