Introduction to Scydmaeninae (Coleoptera, Staphylinidae): morphology of adults

Exo- and endoskeletal structures of Scydmaeninae are illustrated and described based on exemplary 351 species representing 116 genera and all tribes. Over 1700 illustrations show an unparallel morphological diversity of ant-like stone beetles, and introduce this group to coleopterists, setting standards for morphological descriptions. The morphological terminology is discussed and selected terms are defined or clarified, to ensure unambiguous understanding of terms used by various authors in a different sense. Several selected problems are discussed in detail, as the cephalic structures; a possible hypopharyngeal, and not prelabial, origin of the ligula in some beetles; structures that increase the mechanical robustness of the thorax; the astounding plasticity of evolutionary changes in the ventral prothoracic and pterothoracic pleural structures; novel discoveries in the elytral locking system (incl. elytral-metanepisternal locking device); multiple migrations of the aedeagal membranous area retractor; and a parallelism between Scydmaeninae and Pselaphinae in male secondary sexual characters. Moreover, synapomorphies of Scydmaeninae are discussed, and perspectives for future studies are outlined.