Megachile (Eutricharaea) rotundata (Fabricius, 1787)

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 : 40

Megachile (Eutricharaea) rotundata (Fabricius, 1787)

Apis rotundata Fabricius, 1787: 303 . Megachile rotundata ; Gerber and Akre 1969: 1. Jensen 2003: 195. O’Neill and O’Neill 2003: 447; 2011: 223. O’Neill et al.

2004: 619. Pearce 2008: 51. O’Neill et al. 2010: 775. O’Neill et al. 2011: 917. Delphia and O’Neill 2012: 380. Drons 2012:

59. Pearce et al. 2012: 97. O’Neill et al. 2014. O’Neill et al. 2015: 1. Soltani et al. 2017: 827. Donahoo et al. 2021: 444. Megachile (Eutricharaea) rotundata (Fabricius) . Mitchell 1962: 122. Ivanochko 1979: 113. Cooper 1984: 225. Gonzalez 2008:

35. Scott et al. 2011: 54. Sheffield et al. 2011: 31. Kuhlman and Burrows 2017: 12. Reese et al. 2018: 21. Delphia et al.

2019a: 24. Sheffield and Heron 2019: 69. Engel 2020: 10. Apis pacifica Panzer 1798: 16 . Megachile (Eutricharaea) pacifica ; Hurd 1979: 2057.

Diagnosis. The female of M. rotundata can be identified by its white apical setal bands on S2–6 ( Fig. 6A ), white scopal setae on at least the basal half of S5, lateral, ovate fovea on T2, and the absence of lateral, ovate fovea on T3. The females are most similar to M. apicalis (see M. apicalis above). The male of M. rotundata can be identified by its lateral, ovate fovea on T2 and the absence of lateral, ovate fovea on T3. Males of M. rotundata are most similar to M. apicalis (see M. apicalis above).

Notes. Megachile rotundata is an introduced species that is economically important for alfalfa seed production (reviewed in Pitts-Singer & Cane 2011). The first specimen of M. rotundata in Montana is from 1963. Megachile rotundata has now been recorded statewide in Montana ( Fig. 1 AE). It is the only Megachile species that has legal standing in Montana, as the subject of the “Alfalfa Leaf-Cutting Bee Management Act” (2021 Montana Code Annotated Title 80. Agriculture Chapter 6. Apiculture Part 11. Alfalfa Leaf-Cutting Bees). Megachile rotundata are known to nest in a variety of substrates, including cavities, trap nests, and holes in vertical banks (see Discussion: Notes on Megachile (Eutricharaea) rotundata and Introduced Megachile Species ).Photographs, a full morphological description, and notes on its biology 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.