Walteriella, sensu Kasantsev, 1999

Comparisons among Walteriella View in CoL , Neoleiothorax and Stenothemus

The systematic placement of Walteriella remains unclear. Although many congeners were transferred from Lycocerus sensu Okushima 2005 , the aforementioned Walteriella sensu lato (i.e., W. brunnea , W. kasugana and W. sanguinea brevemarginata ) also resembles Neoleiothorax by sharing similar filiform antennae ( Figs. 1C–F View FIGURE 1 , 3B–C, F–M View FIGURE 3 ), pronotum lacking lateral margins on posterior half ( Fig. 2C View FIGURE 2 ), slender and subparallel-sided elytra ( Figs. 1C–F View FIGURE 1 , 3B–C, F–M View FIGURE 3 ) and simple claws ( Fig. 2G View FIGURE 2 ). Neoleiothorax was originally established based on N. kashmirensis ( Fig. 11 View FIGURE ) from Kashmir and currently includes four species ( Wittmer 1978; Švihla 2004; Kopetz 2008). Švihla (2004) suggested an affinity between Neoleiothorax and the Stenothemus genus-group, including Stenothemus , Falsopodabrus Pic, 1927 and Habronychus Wittmer, 1981 , but can be distinguished from the latter genera by its characteristic pronotum. Thus, Walteriella may also be close to this genus-group. Among this group, Walteriella is particularly similar to Stenothemus in possessing simple claws ( Fig. 2G View FIGURE 2 ), although Walteriella sensu stricto exhibits a different claw morphology. Our study further reveals that Walteriella has Stenothemus -like aedeagus that are basally globular and swollen ( Figs. 5–6 View FIGURE 5 View FIGURE 6 ), suggesting their potential affinity. Additionally, Yang et al. (2021) synonymised a species formerly placed in Neoleiothorax with a Stenothemus species (see details in the introduction and the next paragraph), and this species actually aligns with Walteriella sensu lato. This action also supports the possibility that Walteriella may belong to the Stenothemus genus-group and that its generic status warrants re-evaluation.

We compared Walteriella with two morphologically similar genera, Neoleiothorax and Stenothemus . Walteriella can be distinguished from both by its subquadrate to trapezoidal pronotum with rounded and expanded anterior margin and lateral margins either complete or absent on the posterior half ( Fig. 2B–C View FIGURE 2 ) (quadrate to subquadrate, with nearly straight anterior margin in both genera, lateral margins complete in Stenothemus ), elytral surface covered with dense and coarse pubescence ( Fig. 2D–E View FIGURE 2 ) (sparse and fine in both genera) and oval aedeagus with a strongly bent dorsal plate of each paramere forming an apical lock and broad middle emargination ( Figs. 5–6 View FIGURE 5 View FIGURE 6 ) (without such structure in both genera). Therefore, we interpret Walteriella as a genus distinct from both Neoleiothorax and Stenothemus .