This thesis includes the first comprehensive phylogenetic analyses of nitidulid subfamilies represented in the Nearctic region; it also resolves relationships among genera within the subfamily Cryptarchinae. Maximum parsimony analyses were performed on morphological data identified from external morphology and genitalia. The higher-level analysis resulted in the following subfamilial relationships: Carpophilinae (Cillaeinae (Nitidulinae, in part + Epuraeinae (Cryptarchinae (Amphicrossinae (Meligethinae (Nitidulidae, in part + Cybocephalinae)))))). The Cryptarchinae analysis resulted in the following relationships: Cryptarcha (Pityophagus ( Glischrochilus s.str. + Librodor)). Various aspects of color patterns are optimized on the preferred trees from both analyses. Absence of color is plesiomorphic in the Nitidulidae and there are multiple independent origins of color patterns in nitidulids. Feeding habits are optimized on the preferred trees; anthophagy is evidently in the groundplan of nitidulids with mycetophagy and phytophagy appearing very early in nitidulid evolution. The nitidulid fossil record is discussed relative to the origin of angiosperms.