This booklet is based on the author's 1952 MSc thesis. It consists of keys to genera and species (exclusive of the Alleculinae), with the Lagriinae included in the key to genera only. Brief descriptions of each species known to occur or or potentially occur in Ohio are included with the species distribution in the state. Of the 81 species belonging to 44 genera discussed in this paper, 11 have never been collected in Ohio, but are included here either because they are recorded from one or more of the five adjacent states, or are cosmopolitan and likely to eventually be found here. In addition, we record herein three new Ohio state record species: Platydema cyanescens Laporte & Brullé, Gnatocerus guatemalensis (Champion), and Eleates depressus (Randall).