Even though Hadrobunus grandis (Say 1821) is the type species of Hadrobunus, its identity has been uncertain since its original description. The type specimens were collected in coastal Georgia and/or northeastern Florida during the winter of 1817–1818, not from the mid-Atlantic Region (e.g.,Virginia, Maryland) as assumed by some authors. This error has resulted in persistent confusion with H. maculosus (Wood 1868), the dominant Hadrobunus species in the mid-Atlantic region. The type specimens of H. grandis were lost or destroyed, but all surviving evidence suggests that the species known as Leiobunum aurugineum Crosby & Bishop 1924 is a synonym of H. grandis. Examination of available museum specimens revealed two species. Populations east of the Apalachicola River correspond to the historical description of L. aurugineum in having sacculate penes, and are thus identical to H. grandis; those west of the river lack penial sacs and are placed in the new species H. nonsacculatus.