Phyllophaga (Coleoptera: Scarabaeidae) species were collected with a blacklight trap during 1992–1994 at a single site in a relict hardwood forest in central Iowa. There were 1,580 specimens collected, representing 13 species which ranked in proportional abundance from 43.67 to 0.06%. Simpson’s diversity index (D) for species taken in this study was D = 2.87 compared with D = 4.17 for species taken across Iowa in historical data. The disparity in the indices is attributed to the limited ecological habitat sampled compared with available habitats in Iowa. Phyllophaga balia (Say) was the most abundant species (43.67%) in the current study, whereas in the historical data it was an uncommon species (0.02%). Another species, Phyllophaga spreta (Horn), believed to be a truly rare species throughout the midwestern states, was taken in modest numbers (0.95%). This is the first report of this species in Iowa since it’s original description in 1887. Three species from the current study and 8 species derived from historical data are considered to be ecologically rare. It is suggested that the presence of P. spreta may be attributed to the habitat quality at the site.