Megachile (Xanthosarus) gemula Cresson, 1878

Pritchard, Zoe A., Ivie, Michael A., O’Neill, Kevin M. & Delphia, Casey M., 2025, A faunal treatment of the Megachile (Hymenoptera: Megachilidae) of Montana with a key for their identification, Zootaxa 5683 (1), pp. 1-51 : 33

Megachile (Xanthosarus) gemula Cresson, 1878

Megachile gemula Cresson, 1878: 118 . Mitchell 1927b: 178. Drons 2012: 58.

Megachile (Delomegachile) gemula Cresson ; Mitchell 1935b: 181; 1936: 185; 1962: 134. Butler 1965: 6. Hurd 1979: 2059. Ivanochko 1979: 186.

Megachile (Xanthosarus) gemula ; Raw 2002: 36 . Scott et al. 2011: 56. Sheffield et al. 2011: 78. Reese et al. 2018: 23 . Delphia et al. 2019b: 649. Sheffield and Heron 2019: 70.

Diagnosis. The female of M. gemula can be identified by white pubescence on T1–2 that contrasts with the dark pubescence on T3–5, reddish-brown to black scopal setae on S2–6, 4-toothed mandibles with a truncate basal tooth ( Fig. 7E ), and base of mandibles square-shaped (viewed laterally) with parallel sides for a distance as long as wide, then tapering apically ( Fig. 6J ). Females of M. gemula are most similar to M. melanophaea , which have mandibles gradually tapering in width towards apex (from a lateral view) ( Fig. 6I ) and orange scopal setae on S2–6. The male of M. gemula can be identified by its narrow, ventrally excavated probasitarsus, 4-toothed mandibles, and acute posterior angle of the dorsal face of the protibia, the apex entirely dark. The male of M. gemula is most similar to M. melanophaea , in which the dorsal face of the protibia has a rounded and spatulate posterior angle that is entirely cream to pale yellow at the apex.

Notes. Megachile gemula is found widely in Montana though, like many species, has not been extensively collected in eastern regions of the state ( Fig. 1M ). It is known to nest in poplar logs and hollow twigs ( Sheffield et al. 2011). Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011).

Figures

FIGURE 1. County-level distribution of each Megachile species in Montana. Females identified as Megachile latimanus/ Megachile perihirta (and data without recorded specimen sexes) are counted here as M. perihirta as they are not distinguishable from one another in Montana. Males identified as Megachile lapponica/Megachile relativa (and data without recorded specimen sexes) are counted here as M. relativa as they are not distinguishable from one another in Montana. Mitchell county records are included on maps but not in specimen counts. Two specimens did not have county-level localities and are not included in maps but are included in specimen counts.

FIGURE 6. Female Megachile characters. (A) Ventral view of metasoma with white apical setal bands on S2–6, (B) Dorsal view of rounded metasoma, widest at T2–3, (C) Dorsal view of subparallel metasoma, (D–H) Anterior view of clypeus: (D) M. apicalis, (E) M. mellitarsis, (F) M. fidelis, (G) M. lippiae, (H) M. coquilletti, (I) Lateral view of mandible gradually tapering in width towards apex, (J) Lateral view of mandible with base square-shaped with parallel sides for a distance as long as wide, then tapering apically, and (K) Lateral view of mandible square basally, with sides parallel for approximately ⅓ the length of mandible, then tapering apically.

FIGURE 7. Female Megachile characters. (A–H) Anterolateral view of mandible, (I–N) Lateral view of metasoma, tergites 4–6, (O) Lateral view of tergites on M. dakotensis, and (P) Lateral view of head with pronounced tooth on the posterior genal margin on M. pugnata.