Scrapter nitidus (Friese, 1909)

Mack, Anne & Kuhlmann, Michael, 2023, Revision of the nitidus species group of the bee genus Scrapter Lepeletier & Serville, 1828 (Hymenoptera: Apoidea), European Journal of Taxonomy 912, pp. 1-119 : 4-6

The Scrapter nitidus species group

A brief summary of Scrapter species group concepts, in particular the problematic history of the S. nitidus species group, was provided in the introduction. The focus here is on a revised and more consistent morphological definition of this taxon to accommodate species previously placed in other groups. The new broadened concept is also supported by unpublished preliminary molecular phylogenetic data. Eardley's (1996: 42–43) detailed diagnosis of the S. nitidus species group mostly refers to characters of limited diagnostic value when critically assessed based on the far richer Scrapter material available today. Exceptions are the medio-longitudinal depression of the clypeus and the narrow facial fovea.

Following the new definition, species of the S. nitidus species group are:

A) Medium-sized bees of usually 7–9 mm (range about 6–11 mm) body length and

B) characterized by deep and coarse punctation of head and mesosoma (e.g., Figs 26B , 39B–C ).

In combination with at least three of the following features:

C) Clypeus with medio-longitudinal depression (e.g., Figs 13B , 15C ) (clypeus convex: S. flavipes , S. convexus sp. nov.; clypeus flat: S. flavostictus , S. caeruleus sp. nov.).

D) Facial fovea almost linear and narrow, bottom barely visible (e.g., Figs 5B , 39B ) (facial fovea broader: S. basutorum , S. flavipes ).

E) Basal part of propodeum ± horizontal.

F) Males: Metasoma slender ± parallel-sided, about three times as long as broad (less distinct in S. basutorum subgroup and S. confusus subgroup).

G) Males: S7 apicolateral lobes reduced (e.g., Figs 6F , 18F ) (S7 with small apicolateral lobes: S. felicis sp. nov., S. flavipunctatus sp. nov., S. montanus sp. nov., S. pallidicinctus ).

Transitional forms exist that link the S. nitidus group to the closely related “euryglossiform” Scrapter and the relatives of S. aureiferus Cockerell, 1932 and S. calx Eardley, 1996 respectively (the latter form a species group of their own). But species of these two groups are generally distinctly smaller (usually <6 mm) with much finer punctation than in the S. nitidus group and males have a broader and shorter metasoma. Furthermore, “euryglossiform” Scrapter are the smallest bees of the genus and have an even narrower groove-like facial fovea with an invisible bottom but share with the S. nitidus group reduced apicolateral lobes of S7 and the general shape of male genitalia ( Kuhlmann 2014; Kuhlmann & Friehs 2020).

The Scrapter nitidus group can be divided into five subgroups ( Table 1 ) which differ in morphological characters and partly in distribution patterns. Since the phylogeny of the taxa of the Scrapter nitidus species group is unknown, species are listed alphabetically within the subgroups with the latter defined before the species are treated.

Figures

Fig. 26. Scrapter glaberrimus (Friese, 1912), lectotype, ♂ (SAMC). A. Terga 1–2 (dorsal view). B. Genitalia (dorsal view). C. Sternum 7. D. Sternum 8.

Fig. 39. Scrapter obtusus sp. nov., paratype, ♀. A. Lateral view. B. Head (dorsal view). C. Scutum and scutellum (dorsal view). D. Metanotum and propodeum (dorsal view). E. Metasoma (dorsal view). F. Terga 1–2 (dorsal view).

Fig. 13. Scrapter convexoides sp. nov., paratype, ♂ (RCMK). A. Lateral view. B. Scutum and scutellum (dorsal view). C. Metanotum and propodeum (dorsal view). D. Metasoma (dorsal view).

Fig. 15. Scrapter convexus sp. nov., paratype, ♀ (RCMK). A. Lateral view. B. Head (dorsal view). C. Scutum and scutellum (dorsal view). D. Metanotum and propodeum (dorsal view). E. Metasoma (dorsal view). F. Terga 1–2 (dorsal view).

Fig. 5. Scrapter flavipes (Friese, 1925), ♀. A. Lateral view. B. Head (dorsal view). C. Scutum and scutellum (dorsal view). D. Metanotum and propodeum (dorsal view). E. Metasoma (dorsal view). F. Terga 1–2 (dorsal view).

Fig. 6. Scrapter flavipes (Friese, 1925), ♂. A. Lateral view. B. Scutum and scutellum (dorsal view). C. Metanotum and propodeum (dorsal view). D. Metasoma (dorsal view).

Fig. 18. Scrapter crassipunctatus sp. nov., paratype, ♀. A. Lateral view. B. Head (dorsal view). C. Scutum and scutellum (dorsal view). D. Metanotum and propodeum (dorsal view). E. Metasoma (dorsal view). F. Metasoma (dorsal view).