Most small black bugs found in or around mattresses are spider beetles, carpet beetles and bat bugs, according to FMC Professional Solutions. Some people mistake these small black insects for bedbugs, but most bedbugs are brown or red.
Small black bugs come in several forms, including different beetle species, fleas and lice. Most people confuse bedbugs with other insects, but in reality they are a different problem altogether. If the insect does not bite, then it is possible that the insect in question is a carpet beetle. Most lice and fleas feed from humans if no other food source is available, so people see small bites similar to bedbug bites on their legs and arms.