Megachile (Xanthosarus) frigida Smith, 1853

Megachile frigida Smith, 1853: 193 . Drons 2012: 58.

Megachile (Delomegachile) frigida; Mitchell 1942: 116; 1944: 135; 1962: 133. Butler 1965: 6. Hurd 1979: 2059. Ivanochko 1979: 195.

Megachile (Xanthosarus) frigida; Scott et al. 2011: 56. Sheffield et al. 2011: 76. Reese et al. 2018: 22. Delphia et al. 2019a: 25. Delphia et al. 2019b: 649. Sheffield and Heron 2019: 70.

Megachile (Delomegachile) frigida appalachensis Mitchell, 1962: 134 .

Megachile (Delomegachile) vidua var. appalachensis Mitchell, 1935b: 205 .

Megachile vidua, not Smith, 1853 (misidentification); Fultz 2005: 134.

Diagnosis. The female of M. frigida can be identified by its 4-toothed mandibles with a truncate basal mandibular tooth (Fig. 7E), dark brown to black setae on T6, and mostly yellow to orange scopal setae on S6. The female of M. frigida is most similar to M. latimanus / M. perihirta, which has 5-toothed mandibles (Fig. 7F) and orange setae on T6. The male of M. frigida can be identified by its widely expanded and ventrally excavated probasitarsus (Fig. 8B) and two brown stripes on the ventral profemur, which is unique among male Megachile documented in Montana.

Notes. This widespread, distinctive species is found across Montana, though it has been sparsely collected in the eastern half of the state (Fig. 1L). It is known to nest in rotting logs, cavities, and bark mulch (Sheffield et al. 2011; Delphia et al. 2019b). Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011). The voucher for the misidentified specimen (Fultz 2005) is in the MTEC identified as a male M. frigida (MTEC 088592) (Table 2; Supp. Material 2: Erroneous Records).