Status of Nearctic subgenera of Microscydmus revisited (Coleoptera, Staphylinidae, Scydmaeninae)

Nearctic Microscydmus Saulcy & Croissandeau includes species placed in Microscydmus s. str. and subgenera Delius Casey and Neladius Casey. The two latter taxa were originally described as genera, and all Nearctic species of Microscydmus s. str. were placed in a genus Opresus Casey, currently treated as a junior synonym. Detailed examination of the type species of Opresus, Delius and Neladius leads to the following conclusions and changes: Opresus is removed from synonymy with Microscydmus s. str. and placed as a subgenus of Microscydmus; Delius and Neladius are restored as genera. The two latter taxa belong to a group of glandulariine genera characterized by the submentum with lateral sutures, whereas Microscydmus does not have such structures. The type species of the studied genera and subgenera are redescribed: Microscydmus (Opresus) misellus (LeConte), comb. rest., Delius robustulus Casey, comb. rest., and Neladius tenuis Casey, comb. rest. Lectotypes are designated for Scydmaenus misellus LeConte, Delius robustulus Casey and Neladius tenuis Casey.