First description of the larva of Thomson, 1858, with comments on chaetotaxy, pupa, and life history based on two saproxylic species from Europe (Staphylinidae, Aleocharinae, Athetini).

The paper describes the morphological ultrastructure of the previously unknown early (L1) and late larval instars (L2-3) of , including chaetotaxy, pupal cocoon, prepupa, and pupa, based on the saproxylic species Erichson and Gravenhorst. Diagnostic larval characters for the genus are given for the first time. Morphological differences between mature larvae of these two species relate to the colouration and degree of flattening of the body, details of antennal structure, anterior margin of the labrum, mandibles, and mala. The differences are relatively small, probably because of the similar ecological preferences of both species. As in the case of other aleocharine larvae, L1 in differs from L2-3 in the lack of some setae on the dorsal surface of the head and thorax, and on the abdominal tergites and sternites; the presence of a subapical seta on the urogomphi; egg bursters on some thoracic and abdominal tergites; a darker antennal segment III; and the relatively longer urogomphi and their apical setae. The differences established in the features of the chaetotaxy of L1 and L2-3 between Athetini (), Oxypodini () and Homalotini () correspond with the molecular marker-based relationships of these taxa.