taxonID	type	description	language	source
03C17C29FFFBFF8273BD7980925272BC.taxon	discussion	This key was written based on previous works by Mitchell (1924, 1926 a, 1927 a, 1927 b, 1934, 1935 a, 1935 b, 1936, 1937 a, 1937 b, 1937 c, 1937 d, 1962, 1980), Ivanochko (1979), Sheffield et al. (2011), and Bzdyk (2012) (see also Sheffield 2020) and includes both sexes of the species that have been documented in Montana, their possible color variants, as well as species we most expect (based on their distributions or expected spread) to eventually be found in the state. We suggest reading the Taxonomic Challenges before using the key for greater ease of use and better understanding. Difficulties in identifying Megachile to species often arise with specimens that were old when collected (i. e., they display wing and mandibular wear), grimy specimens, and specimens with closed mandibles or leg positioning that may obscure characters. Specimens may be re-washed in hot water and soap to remove grime from setae or teeth and then carefully blow-dried. If the mandibles are closed, opening the mandibles of a relaxed specimen using a pin may be useful. Similarly, repositioning the legs away from the body of a relaxed specimen can help for viewing certain characters, especially in males, as can extending / separating the individual tergites from one another to reveal the basal half, especially tergite 6 from tergite 5, in females. The genus Megachile is characterized by having two submarginal cells subequal in length, no arolium between the tarsal claws, a labrum that is longer than wide, an apically depressed first metasomal tergite, and 3 - jointed maxillary palpi. Females display scopa on the sternites, and males display a preapical carina on tergite 6 (Mitchell 1934; Michener 2007; Burrows et al. 2021). Users should refer to Michener, McGinley, and Danforth (1994) to first identify specimens to the genus Megachile. Entomological terms follow Torre-Bueno (1989). Certain species key out multiple times to account for variation in characters.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFFBFF8273BD7980925272BC.taxon	description	T 1 – T 6: Tergites on the dorsal surface of the metasoma.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF0FF8373BD7ED4919571B1.taxon	diagnosis	Diagnosis. The female of M. angelarum can be recognized by its subparallel metasoma (viewed dorsally) (Fig. 6 C), mandibles without cutting edges, clypeal margin that is medially emarginate and laterally crenulate, white T 5 apical setal band which is similar in width and appearance to the T 1 – 4 apical setal bands, vertex of head with small, dense punctation (ca. 8 – 10 punctures between lateral ocelli and posterior margin of vertex), and a smooth, shiny, impunctate occipital suture. The female of M. angelarum is most similar to M. campanulae, which has a medially incomplete T 5 white apical setal band that is thinner and less plumose than those on T 1 – 4, and large, sparse punctation on the vertex of head (ca. 4 – 6 punctures between lateral ocelli and posterior margin of vertex) (see Taxonomic Challenges). The male of M. angelarum can be distinguished by its retracted S 4 and dense punctation on the vertex of the head (ca. 9 punctures between lateral ocelli and posterior margin of vertex). Male M. angelarum are most similar to M. campanulae, which have large, sparse punctation on the vertex of the head (ca. 4 punctures between lateral ocelli and posterior margin of vertex).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF0FF8373BD7ED4919571B1.taxon	discussion	Notes. These mason bees use plant resins, not leaves, to construct nest cells in existing cavities and are therefore not leafcutting bees. This species was first recorded in the published literature from Montana in 2017 from Missoula County, though the earliest recorded specimen year is 2015 (Kuhlman & Burrows 2017; Table 1). It is now known from five counties in Western Montana (Fig. 1 A). For further details on identification issues see Taxonomic Challenges. Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF0FF8473BD7A6191957400.taxon	diagnosis	Diagnosis. The female of M. anograe can be distinguished by its 3 - toothed mandibles (Fig. 7 A) and a smooth and shiny T 6 with well-separated punctures (3 – 5 diameters apart). For information on the rare melanistic form (not seen in Montana) see Taxonomic Challenges. In Montana, females of this species are only likely to be confused with M. pascoensis, which also has 3 - toothed mandibles, but in M. pascoensis T 6 is pitted and dull with closely spaced punctures (≤ 1 diameter apart). The male of M. anograe can be distinguished by its wide and spatulate procoxal spine (Fig. 8 I), medially and laterally emarginate clypeus (Fig. 10 B), fovea on the dorsal metafemur, and apicomedial setal patch on S 5 (Fig. 10 G). Males of M. anograe are most similar to M. pascoensis, but the clypeal margin is much more deeply emarginate medially in M. pascoensis (Fig. 10 A). For further details on identification issues see Taxonomic Challenges.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF0FF8473BD7A6191957400.taxon	discussion	Notes. At the continental scale, M. anograe and M. pascoensis are in general allopatric, with M. anograe east of the continental divide and M. pascoensis to the west. This division so far holds in Montana. Megachile anograe is the more common of the two in Montana, occurring in the drier southern and central counties east of the divide (Fig. 1 B) while the rarer M. pascoensis is known only from the wetter northwest Montana west of the divide (Fig. 1 AA). Sheffield et al. (2011) report melanistic forms in the western U. S., though we did not find them in Montana. Photographs, a full morphological description, and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF7FF8473BD7EF1934A7102.taxon	diagnosis	Diagnosis. The female of M. apicalis can be identified by the white apical setal bands on S 2 – 6 (Fig. 6 A), black scopal setae on S 5, and lateral, ovate fovea on T 2 and T 3. Females of M. apicalis are most similar to M. rotundata, which have white scopal setae on S 5 and lateral, ovate fovea on T 2 only. The male of M. apicalis can be distinguished by the lateral, ovate fovea on T 2 and T 3. Males of M. apicalis are most similar to M. rotundata, which have lateral, ovate fovea on T 2 only.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF7FF8473BD7EF1934A7102.taxon	discussion	Notes. Megachile apicalis is an accidentally introduced species in the United States, first collected in Montana in 2013 from localities in Deer Lodge, Sanders, and Lake Counties. It was first documented in the literature by Kuhlman & Burrows (2017). This species may contribute to pollination of the invasive yellow star-thistle (Centaurea solstitialis), though not as strongly as A. mellifera (Barthell et al. 2001). Megachile apicalis is currently present in western Montana but is expected to spread further (Fig. 1 C). It is established on both coasts of the U. S. and seems to be moving into Montana from the Pacific Northwest region (see Discussion: Notes on Megachile (Eutricharaea) rotundata and Introduced Megachile Species). Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF7FF8473BD7BFE9444723A.taxon	diagnosis	Diagnosis. The females of M. brevis can be identified by the usually all pale yellowish white scopal setae on S 2 – S 6 (except occasionally black scopal setae on the apical half of S 6; see Taxonomic Challenges), 4 - toothed mandibles with an even, semicircular emargination between the 3 rd and 4 th teeth (Fig. 7 B), appressed white setae on T 6, and the “ pinched shape ” of T 6, which is convex basally and concave apically (viewed laterally) (Fig. 7 K). The females of M. brevis are most similar to M. onobrychidis, which has entirely black scopal setae on S 6 and black setae on T 6. For further details on identification issues see Taxonomic Challenges. The males of M. brevis can be identified by the narrow probasitarsus, which is not excavated ventrally (Fig. 8 A), tomentose, white setae on T 6, and weakly emarginate transverse carina on T 6 (Fig. 9 B).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF7FF8473BD7BFE9444723A.taxon	discussion	Notes. Megachile brevis is a commonly collected species found widely in Montana (Fig. 1 D) that nests in a variety of substrates (Sheffield et al. 2011). Photographs, illustrations, full morphological descriptions, and notes on the biology of this species can be found in Sheffield et al. (2011) and Bzdyk (2012).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF6FF8573BD7FD0920871DF.taxon	diagnosis	Diagnosis. The female of M. campanulae can be identified by its subparallel metasoma (viewed dorsally) (Fig. 6 C), mandibles without cutting edges, clypeal margin that is medially emarginate and laterally crenulate, a medially incomplete T 5 apical setal band that is thinner and less plumose than T 1 – 4 apical setal bands, vertex of head with large, sparse punctation (ca. 4 – 6 punctures between lateral ocelli and posterior margin of vertex), close and evenly spaced scutum punctation compared to irregular and inconsistent scutellum punctation, and a line of punctures on the occipital suture appearing as a slight carina. Females of M. campanulae are most similar to M. angelarum (see M. angelarum above) (see Taxonomic Challenges). The male of M. campanulae can be identified by its retracted S 4 and large, sparse punctation on the vertex of the head (ca. 4 punctures between lateral ocelli and posterior margin of vertex). Males of M. campanulae are most similar to M. angelarum (see M. angelarum above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF6FF8573BD7FD0920871DF.taxon	discussion	Notes. In Montana, M. campanulae has been collected in scattered western and eastern localities (Fig. 1 E). These mason bees use plant resins, not leaves, to construct nest cells in existing cavities or trap nests (O’Neill & O’Neill 2016) and are therefore not leafcutting bees. Because of misidentifications noted above in the synonymical table, the morphological description of the female in Sheffield et al. (2011) is not accurate. See Table 2, Supplementary Material 2: Erroneous Records, and Taxonomic Challenges for further explanation. The vouchers for the misidentified specimens (Reese et al. 2018; Burkle et al. 2020; LaManna et al. 2020) are in the Burkle Community Ecology Lab at Montana State University identified as female M. campanulae (5718 LR, 19730 CHS, 68812 LR, 64728 LR, 1725 CHS, 73 A 817 LR). The vouchers for the misidentified specimens (Delphia et al. 2019 b) are in the O’Neill Research Collection at Montana State University identified as female M. campanulae (KMOC # 1435, KMOC # 1436, KMOC # 1437) (Table 2).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF6FF8573BD7A4C910D7235.taxon	diagnosis	Diagnosis. The female of M. casadae can be identified by a shiny and sparsely punctate clypeus medially, 4 - toothed mandibles with an asymmetrical emargination between the 3 rd and 4 th teeth that is deepest closer to the 4 th tooth (Fig. 7 C), black scopal setae on S 6, and T 6 with an elevated ridge apicomedially (appears laterally “ pinched ” in dorsal profile), with dense brown setae along ridge directed medially. The male of M. casadae can be identified by 3 - toothed mandibles, wide and spatulate procoxal spines (Fig. 8 I), and a slight medial emargination in its otherwise mostly straight clypeal margin (Fig. 10 C).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF6FF8573BD7A4C910D7235.taxon	discussion	Notes. This species is a new state record for Montana. Megachile casadae is most common to the south of Montana (Fig. 1 F) and reaches its northernmost extent in Montana, east of the divide, and southern Alberta. Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF5FF8673BD7C4D91387031.taxon	diagnosis	Diagnosis. The female of M. coquilletti can be distinguished by its moderately concave T 6 (Fig. 7 M) with brown to black setae (often with suberect pale setae in small patches laterally), 4 - toothed mandibles with a semicircular, symmetrical emargination between the 3 rd and 4 th teeth (Fig. 7 B), and long transverse medial carina on the apical margin of the clypeus (four times as long as diameter of median ocellus) (Fig. 6 H). Females are difficult to distinguish from M. lippiae, which has suberect pale setae and erect black setae on T 6 and a short medial carina on the apical margin of the clypeus (two times as long as diameter of median ocellus) (Fig. 6 G). For further details on identification issues see Taxonomic Challenges. The male of M. coquilletti can be distinguished by its narrow probasitarsus (Fig. 8 A), which is not excavated ventrally, and light to dark yellow coloration on tarsomeres 2 – 4.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF5FF8673BD7C4D91387031.taxon	discussion	Notes. This species has been collected in central and western Montana (Fig. 1 H). Photographs, illustrations, full morphological descriptions, and notes on the biology of this species can be found in Sheffield et al. (2011) and Bzdyk (2012).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF5FF8673BD7FD0949277DD.taxon	diagnosis	Diagnosis. The female of M. centuncularis can be identified by its 5 - toothed mandibles with evenly deep emarginations between all teeth (Fig. 7 G), black setae on T 6, and yellow to orange scopal setae on S 2 – 6. It is most similar to M. relativa, which has golden setae on T 6. The male of M. centuncularis can be identified by its narrow brown to black probasitarsi (Fig. 8 A), sparse setae on T 6, absence of a procoxal spine, and absence of a median tubercle on the clypeus. The male of M. centucularis is most similar to M. lapponica / M. relativa, which has a small triangular median tubercle on the clypeal margin.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF5FF8673BD7FD0949277DD.taxon	discussion	Notes. This species is a new state record for Montana, though it is widespread elsewhere in North America. In Montana, it has been sparsely collected in a few western localities (Fig. 1 G). Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF5FF8673BD7AE194327295.taxon	diagnosis	Diagnosis. The female of M. dakotensis can be identified by the shape of T 3 – 5, which are strongly concave between the depressed apical and basal grooves (Fig. 7 O), reddish tibiae apically, and the asymmetrical emargination between its 3 rd and 4 th (basal) teeth with emargination deepest closer to the 4 th tooth (Fig. 7 C). The male of M. dakotensis can be identified by its procoxal spine (Fig. 8 H), which is longer than wide, reddish tibiae apically (front tibiae can be yellowish apically), and the shape of T 2 – 4, which are strongly concave between the depressed apical and basal grooves (Fig. 10 D).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF5FF8673BD7AE194327295.taxon	discussion	Notes. Mitchell (1937 a) recorded this species from Montana without a more specific locality, and since then, only two specimens have been collected in Montana, both at Medicine Rocks State Park, near the eastern border, in 2020 (Fig. 1 I). We have been unable to locate Michell’s voucher. This rarely collected species was first described in Mitchell 1926 b, then redescribed in Mitchell (1937 a) and Mitchell (1962) with male characters illustrated. Photographs of both sexes can be found on BOLD (http: // www. barcodinglife. org).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF4FF8773BD7C7493F0701D.taxon	diagnosis	Diagnosis. The female of M. fidelis is distinguished by its subparallel metasoma (viewed dorsally) (Fig. 6 C) and clypeal margin with two prominent, wide, lateral tubercles surrounding a median triangular tubercle (Fig. 6 F), which is unique among documented Montana Megachile species. The male of M. fidelis is distinguished by its thin and narrowly pointed procoxal spine (Fig. 8 H) and its widely expanded and ventrally excavated probasitarsus (Fig. 8 B) with dark setae along the entire posterior edge of the scoop-shaped dilation. The male of M. fidelis is most similar to M. pugnata, which has dark setae along only the basal ⅓ of the posterior edge of the scoop-shaped dilation.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF4FF8773BD7C7493F0701D.taxon	discussion	Notes. This species has been recorded mainly in western Montana (Fig. 1 K), with one record further east in Musselshell County, but it would be expected to be found in the eastern half of the state due to a record of M. fidelis from the Black Hills of South Dakota (Drons 2012). Photographs, a full morphological description, and notes on the biology of this cavity-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF4FF8773BD7FD090E97787.taxon	diagnosis	Diagnosis. The female of M. dentitarsus can be identified by its consistently wide, white apical setal bands on T 3 – 5 and its 5 - toothed mandibles (Fig. 7 F), with the deepest emargination between the 3 rd and 4 th tooth, strongly angled towards the 4 th tooth. Females are most commonly confused with M. latimanus / M. perihirta females, which have medially incomplete apical setal bands. The male of M. dentitarsus can be identified by its widely expanded and ventrally excavated probasitarsus (Fig. 8 B), the smooth, glabrous ventral protuberance on its mesobasitarsus (Fig. 8 D), and the small spine on the ventral mesepisternum (viewed ventrally, directly anterior to mesocoxa). Males are most similar to M. perihirta, in which the ventral mesepisternum (viewed ventrally, directly anterior to mesocoxa) has a smooth, spineless carina instead of a spine.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF4FF8773BD7FD090E97787.taxon	discussion	Notes. In Montana, this species is widespread east of the continental divide (Fig. 1 J). Photographs, a full morphological description, and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF4FFB873BD7A8D94D17478.taxon	diagnosis	Diagnosis. The female of M. frigida can be identified by its 4 - toothed mandibles with a truncate basal mandibular tooth (Fig. 7 E), dark brown to black setae on T 6, and mostly yellow to orange scopal setae on S 6. The female of M. frigida is most similar to M. latimanus / M. perihirta, which has 5 - toothed mandibles (Fig. 7 F) and orange setae on T 6. The male of M. frigida can be identified by its widely expanded and ventrally excavated probasitarsus (Fig. 8 B) and two brown stripes on the ventral profemur, which is unique among male Megachile documented in Montana.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFF4FFB873BD7A8D94D17478.taxon	discussion	Notes. This widespread, distinctive species is found across Montana, though it has been sparsely collected in the eastern half of the state (Fig. 1 L). It is known to nest in rotting logs, cavities, and bark mulch (Sheffield et al. 2011; Delphia et al. 2019 b). 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).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCBFFB873BD7BC891F9739B.taxon	diagnosis	Diagnosis. The female of M. gentilis can be identified by the black scopal setae on S 6, white scopal setae on S 2 – 5, and 4 - toothed mandibles with an angulate basal mandibular tooth appearing as a weak additional tooth (i. e., 5 - toothed) (Fig. 7 D). The female of M. gentilis is closest to M. mendica, which has mostly yellow to light orange scopal setae on S 6 but can approach ca. 50 % black scopal setae apically. For further details on identification issues see Taxonomic Challenges. The male of M. gentilis can be identified by its narrow probasitarsus, which is not excavated ventrally, T 5 without a white apical setal band (may have some setae laterally), and T 4 – 5 dull with punctures ca. 1 diameter apart. The male of M. gentilis is closest to M. mendica, in which T 4 – 5 is polished and shiny, with punctures 2 – 4 diameters apart.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCBFFB873BD7BC891F9739B.taxon	discussion	Notes. This species is a new state record for Montana and has been collected from scattered localities in central and western Montana (Fig. 1 N). Megachile gentilis nests in natural cavities as well as trap nests (Sheffield et al. 2011). Photographs, illustrations, full morphological descriptions, and notes on its biology can be found in Sheffield et al. (2011) and Bzdyk (2012).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCBFFB873BD7E299195715B.taxon	diagnosis	Diagnosis. The female of M. gemula can be identified by white pubescence on T 1 – 2 that contrasts with the dark pubescence on T 3 – 5, reddish-brown to black scopal setae on S 2 – 6, 4 - toothed mandibles with a truncate basal tooth (Fig. 7 E), and base of mandibles square-shaped (viewed laterally) with parallel sides for a distance as long as wide, then tapering apically (Fig. 6 J). Females of M. gemula are most similar to M. melanophaea, which have mandibles gradually tapering in width towards apex (from a lateral view) (Fig. 6 I) and orange scopal setae on S 2 – 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.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCBFFB873BD7E299195715B.taxon	discussion	Notes. Megachile gemula is found widely in Montana though, like many species, has not been extensively collected in eastern regions of the state (Fig. 1 M). 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).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCBFFB973BD780594BF74B4.taxon	diagnosis	Diagnosis. The female of M. inermis can be identified by its distinctively large body size (17 – 20 mm long), shiny clypeus with sparse punctation medially (punctures 1 – 3 diameters apart), and clypeal margin with four prominent tubercles. The male of M. inermis can be identified by its large body size (11 – 16 mm long), unevenly spaced 3 - toothed mandibles (2 nd tooth closer to apical tooth), and its nub-like procoxal spine, which is wider than long and covered with a small tuft of dense orange setae. Males are most similar to M. montivaga, which has evenly spaced teeth.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCBFFB973BD780594BF74B4.taxon	discussion	Notes. Megachile inermis, a distinctively large species, has been recorded in several localities in western Montana (Fig. 1 O). This species is known to nest in cavities and rotting logs (Sheffield et al. 2011). Photographs, a full morphological description, and notes on its biology can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCAFFB973BD7D659302704F.taxon	diagnosis	Diagnosis. The females of M. lapponica can be identified by their 5 - toothed mandibles with evenly deep emarginations between teeth (Fig. 7 G), brown to black scopal setae on S 6, and scopal setae on S 5 black apically and yellow to pale orange basally. The female of M. lapponica is most similar to M. relativa, which has golden scopal setae on S 6, and M. centuncularis, which has black setae on T 6. The males of M. lapponica cannot be reliably separated from males of M. relativa in Montana based on external morphology or by examining the genitalia (see Taxonomic Challenges; Sheffield & Westby 2007). Males of M. lapponica / M. relativa can be recognized by the absence of a procoxal spine, small median triangular tubercle on the clypeal margin, narrow brown to black probasitarsi, evenly spaced 3 - dentate mandibles, and T 6 with sparse setae, not tomentose. Megachile lapponica / M. relativa is most similar to M. centuncularis (see M. centuncularis above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCAFFB973BD7D659302704F.taxon	discussion	Notes. Megachile lapponica females have been found in scattered localities across the western half of Montana (Fig. 1 P). Photographs, a full morphological description (but see Taxonomic Challenges), and notes on the biology of M. lapponica can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCAFFBA73BD7A3C932B75B0.taxon	diagnosis	Diagnosis. The females of M. latimanus cannot be reliably separated from M. perihirta in Montana based on morphology (see Taxonomic Challenges). Megachile latimanus / M. perihirta have 5 - toothed mandibles with the deepest emargination between the 3 rd and 4 th teeth, emargination strongly angled towards the 4 th tooth (Fig. 7 F), and medially incomplete apical setal bands on T 3 – 5. Females are most similar to M. dentitarsus, which has T 3 – 5 apical setal bands consistently wide, as wide medially as laterally. The male of M. latimanus can be identified by its widely expanded and ventrally excavated probasitarsus (Fig. 8 B), the wide, rounded, ventral protuberance of the mesobasitarsus basally (viewed anteriorly) (Fig. 8 C), and the widely depressed ventral side of the mesofemur. Males are most similar to M. perihirta, which has mesobasitarsus with narrowly rounded, ventral protuberance basally (Fig. 8 D) and the smooth, convexly rounded ventral side of mesofemur.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCAFFBA73BD7A3C932B75B0.taxon	discussion	Notes. Megachile latimanus has been recorded in a few scattered localities across Montana (Fig. 1 Q). Photographs, a full morphological description (but see Taxonomic Challenges), and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC9FFBA73BD7E619105715C.taxon	diagnosis	Diagnosis. The female of M. lippiae can be identified by its suberect white setae and erect black setae on T 6 and apically concave T 6 (viewed laterally) (Fig. 7 N). The female is difficult to discern from M. coquilletti (see M. coquilletti above) (see Taxonomic Challenges). The male of M. lippiae can be identified by its narrow probasitarsus, which is not excavated ventrally, the apical margin of T 6 (ventrad to the transverse carina) with submedian teeth closer to lateral teeth than to each other (Fig. 9 F), the scutum with less than 25 % black pubescence, and mostly white pubescence on the dorsal tergites and vertex of head. The male of M. lippiae is most similar to M. texana, which has greater than 50 % black pubescence on the scutum, tergites with significant bands of black pubescence, and the vertex of head with greater than 50 % black pubescence (see Taxonomic Challenges).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC9FFBA73BD7E619105715C.taxon	discussion	Notes. Megachile lippiae has been collected widely across Montana (Fig. 1 R). Photographs, illustrations, full morphological descriptions, and notes on the biology of this species can be found in Sheffield et al. (2011) and Bzdyk (2012). Sheffield and Genaro (2013) briefly made a claim of validity for Megachile cleomis Cockerell. See Taxonomic Challenges above for a discussion of this issue. The voucher for the misidentified specimen (Pearce 2008) is in the MTEC identified as a male M. lippiae (MTEC 088326) (Table 2; Supp. Material 2: Erroneous Records).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC9FFBA73BD7BCD92A0739B.taxon	diagnosis	Diagnosis. The female of M. manifesta can be identified by its 4 - toothed mandibles with an asymmetrical emargination between the 3 rd and 4 th teeth that is deepest nearer the 4 th tooth (Fig. 7 C), black scopal setae on S 6 and at least the apical part of S 5, the basal portion with white scopal setae, and T 5 surface matte to shiny with punctures ≤ 1 diameter apart medially. Females are closest to M. nevadensis, which has all white scopal setae on S 5, and M. wheeleri, which has the surface of T 5 polished and shiny with punctures 2 – 4 diameters apart medially (see Taxonomic Challenges). The male of M. manifesta can be identified by its wide and spatulate procoxal spine without a setae patch at the base (Fig. 8 I), triangular metatarsomeres (viewed laterally) (Fig. 8 F), and a smooth, rounded carina on the ventral mesepisternum (viewed ventrally, directly posterior to the procoxal spine). The male of M. manifesta is most similar to M. wheeleri, which differs in having quadrate metatarsomeres (viewed laterally) (Fig. 8 G).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC9FFBA73BD7BCD92A0739B.taxon	discussion	Notes. This species, in general occurring in the western U. S. and Canada, is found in drier areas of eastern and south-central Montana (Fig. 1 S). Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC9FFBB73BD7808910D771D.taxon	diagnosis	Diagnosis. The female of M. melanophaea can be distinguished by its white pubescence on T 1 – 2, contrasting the dark pubescence on T 3 – 5, orange scopal setae on S 2 – 6, and mandibles gradually tapering in width from base to apex (viewed laterally) (Fig. 6 I). The female of M. melanophaea is most similar to M. gemula (see M. gemula above). The male of M. melanophaea can be identified by its 4 - toothed mandibles and the dorsal face of the protibia, which has a rounded, spatulate posterior angle and an entirely pale apex. The male of M. melanophaea is most similar to M. gemula (see M. gemula above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC9FFBB73BD7808910D771D.taxon	discussion	Notes. This species has been collected widely in Montana, with sparser records in the eastern part of the state, reflecting the general trend of more intensive collecting in the western portion of the state (Fig. 1 T). Photographs, a full morphological description, and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC8FFBB73BD7A2193CB72D5.taxon	diagnosis	Diagnosis. The female of M. mendica is distinguished by its mostly yellow to orange scopal setae on S 5 and S 6, with only a few black scopal setae, T 6 straight (viewed laterally) (Fig. 7 J) with brown appressed setae, and 4 - toothed mandibles with an angulate basal tooth, appearing as a weak additional tooth (i. e., 5 - toothed) (Fig. 7 D). Females of M. mendica are most similar to M. gentilis (see M. gentilis above), and M. snowi, which has white appressed setae on T 6 (M. snowi is a prior subspecies of M. mendica; Byzdk 2012). The male of M. mendica is distinguished by its narrow probasitarsus, which is not excavated ventrally (Fig. 8 A), T 5 without a white apical setal band, and T 4 – 5 polished and shiny with punctures 2 – 4 diameters apart. The male of M. mendica is most similar to M. gentilis (see M. gentilis above) and M. snowi, which differs in having a complete T 5 white apical setal band.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC8FFBB73BD7A2193CB72D5.taxon	discussion	Notes. This species is a new state record for Montana and has only been collected from two localities in eastern Montana (Fig. 1 V). Photographs, illustrations, full morphological descriptions, and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011) and Bzdyk (2012).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC8FFBB73BD7D8D91957071.taxon	diagnosis	Diagnosis. The female of M. mellitarsis can be distinguished by the two broadly incurved emarginations on its clypeal margin (Fig. 6 E), 4 - toothed mandibles with evenly deep emarginations between all teeth, and reddish-brown tarsi contrasting the black tibia on the legs. The male of M. mellitarsis can be distinguished by the thin, narrowly pointed procoxal spine (Fig. 8 H), orangish brown meso- and metatarsi, and the distinctly yellow protarsi with elongated apical dilation that reaches apex of the 3 rd tarsomere. The male of M. mellitarsis is closest to M. pugnata and M. fidelis, both of which have front basitarsi with apical dilation not reaching 3 rd tarsomere. For more details on identification issues see Taxonomic Challenges.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC8FFBB73BD7D8D91957071.taxon	discussion	Notes. This species is a new state record for Montana. Other than a record from British Columbia’s Western Interior Basin (Sheffield 2019), this dry-land species is at the northern edge of its known range in southern Montana (Fig. 1 U). Photographs, a full morphological description, and notes on the biology of this species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCFFFBD73BD794B937675B0.taxon	diagnosis	Diagnosis. The female of M. onobrychidis can be identified by the shape of T 6, which is strongly convex basally and concave apically (Fig. 7 K), black setae on T 6, 4 - toothed mandibles with an even semicircular emargination between the 3 rd and 4 th teeth (Fig. 7 B), and black scopal setae on S 6. The females are most similar to M. brevis (see M. brevis above). The male of M. onobrychidis can be identified by the sparse setae on T 6, the shape of the procoxal spine, which is longer than wide, and the shorter ocelloccipital distance compared to the ocellocular distance (Fig. 8 L).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCFFFBD73BD794B937675B0.taxon	discussion	Notes. Megachile onobrychidis is found across Montana, though like many other species, has been less collected in eastern parts of the state (Fig. 1 Y). Photographs, illustrations, full morphological descriptions, and notes on its biology can be found in Sheffield et al. (2011) and Bzdyk (2012).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCFFFBC73BD7FD092A477B2.taxon	diagnosis	Diagnosis. The female of M. montivaga is distinguished by its light yellow to orange scopal setae on S 2 – S 6, appressed cream-colored setae on T 6, its 5 - toothed mandibles, which have no cutting edge ventrad the tooth plane, and an elevated ridge running dorsally from the apex of the 2 nd tooth to the point of attachment of the mandible (Fig. 7 H). The male of M. montivaga is distinguished by its three evenly spaced mandibular teeth and its nub-like procoxal spine, which is wider than long and covered with a small tuft of dense orange setae. The male of M. montivaga is most similar to M. inermis (see M. inermis above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCFFFBC73BD7FD092A477B2.taxon	discussion	Notes. Megachile montivaga has been widely collected in western Montana and from a few eastern localities (Fig. 1 W). It is known to nest in soil and old stems. Photographs, a full morphological description, and notes on its biology can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCFFFBC73BD7C6F93A170DE.taxon	diagnosis	Diagnosis. The female of M. nevadensis can be identified by its black scopal setae on S 6, white scopal setae on S 5, T 5 with punctures ≤ 1 diameter apart medially, and 4 - toothed mandibles with an asymmetrical emargination between the 3 rd and 4 th teeth that is deepest nearer the 4 th tooth (Fig. 7 C). The females are most similar to M. manifesta (see M. manifesta above) and M. wheeleri, which has T 5 with punctures 2 – 4 diameters apart medially (see Taxonomic Challenges). The male of M. nevadensis can be identified by its 3 - toothed mandibles, its wide and spatulate procoxal spine (Fig. 8 I), with a short, suberect patch of setae at the base, and carina on mesepisternum with long setae touching the hind coxae. The males are most similar to M. wheeleri and M. manifesta, neither of which have a patch of setae at the base of the procoxal spine.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCFFFBC73BD7C6F93A170DE.taxon	discussion	Notes. This species was recorded from Bozeman, Montana, by Mitchell (1937 a), but we were unable to locate the voucher (see Discussion: Searching for Mitchell’s Montana Species). However, collecting in eastern Montana resulted in collection of one male specimen of M. nevadensis in 2021 (Fig. 1 X). The species was first described in Cresson (1879), then redescribed in more detail in Mitchell (1937 a) with illustrations of male characters. Photographs of both sexes can be found on BOLD (http: // www. barcodinglife. org).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCEFFBD73BD7E61951C767C.taxon	diagnosis	Diagnosis. The female of M. parallela can be identified by the upcurve at the apical end of S 6, which extends past T 6 (Fig. 7 L) and the appressed white to yellow setae on T 6. The male of M. parallela can be identified by the two pairs of prominent teeth on the apical margin of T 6, (Fig. 9 C) and large, semi-circular emargination of the pre-apical carina of T 6.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCEFFBD73BD7E61951C767C.taxon	discussion	Notes. This species is recorded from localities across Montana (Fig. 1 Z). Photographs, a full morphological description, and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCEFFBD73BD7C2D952F7002.taxon	diagnosis	Diagnosis. The female of M. pascoensis can be identified by its 3 - toothed mandibles (Fig. 7 A) and pitted, dull T 6 with punctures ≤ 1 diameter apart. The females are most similar to M. anograe (see M. anograe above). The male of M. pascoensis can be identified by its clypeal margin, which has a deep U-shaped median emargination (as deep as wide) (Fig. 10 A) and the white apical setal band on T 5.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCEFFBD73BD7C2D952F7002.taxon	discussion	Notes. This distinctive species is rare outside of California. In Montana, it is known from a historical record (Mitchell 1934) and two specimens from Missoula County (Kuhlman & Burrows 2017) (Fig. 1 AA). The species was first described in Mitchell (1934) (male = M. pascoensis; female = M. gabrielensis) and has not been redescribed or illustrated since. Photographs of the types of both sexes can be found on Big-Bee (Seltmann et al. 2021).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCEFFBE73BD7AFE93157400.taxon	diagnosis	Diagnosis. The females of M. latimanus and M. perihirta cannot be reliably separated in Montana based on morphology (see M. perihirta above) (see Taxonomic Challenges). Megachile latimanus / M. perihirta has 5 - toothed mandibles with the deepest emargination between the 3 rd and 4 th teeth, emargination strongly angled towards the 4 th tooth (Fig. 7 F), and medially incomplete apical setal bands on T 3 – 5. The male of M. perihirta can be identified by its widely expanded probasitarsus (Fig. 8 B), which is excavated ventrally, narrowly rounded, ventral protuberance on its basal mesobasitarsus (viewed anteriorly) (Fig. 8 D), and smooth, convexly rounded anterior mesofemur. The males are most similar to M. dentitarsu s (see M. dentitarsus above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCEFFBE73BD7AFE93157400.taxon	discussion	Notes. Megachile perihirta is a common, widespread species in Montana (Fig. 1 AB). Photographs, a full morphological description (but see Taxonomic Challenges), and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011). The vouchers for the misidentified specimens (Simanonok 2018) are in the Burkle Community Ecology Lab at Montana State University identified as female M. latimanus / M. perihirta (8713 MS 16, 19715 EE, 20725 MS 16, 11617 MS 16, 9721 EE) (Table 2; Supp. Material 2: Erroneous Records). The voucher for the misidentified specimen (Adhikari et al. 2019) is in the MTEC identified as a male M. perihirta (MTEC 035028) (Supp. Material 2: Erroneous Records).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCDFFBE73BD7B8A91EA72F2.taxon	diagnosis	Diagnosis. The female of M. relativa can be identified by its 5 - toothed mandibles (Fig. 7 G), yellow-orange scopal setae on S 2 – 6, and golden pubescence on T 6. The females are most similar to M. centuncularis (see M. centuncularis above). The males of M. relativa cannot be reliably separated from males of M. lapponica in Montana based on external morphology or by examining the genitalia (see Taxonomic Challenges; Sheffield & Westby 2007). Males of M. lapponica / M. relativa can be recognized by the absence of a procoxal spine, small median triangular tubercle on the clypeal margin, narrow brown to black probasitarsi (Fig. 8 A), evenly spaced 3 - dentate mandibles, and T 6 with sparse setae, not tomentose. Megachile lapponica / M. relativa is most similar to M. centuncularis (see M. centuncularis above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCDFFBE73BD7B8A91EA72F2.taxon	discussion	Notes. In Montana, this species has been collected widely but with only a few eastern localities, reflecting the general lack of collecting in the region (Fig. 1 AD). Photographs, a full morphological description (but see Taxonomic Challenges), and notes on its biology can be found in Sheffield et al. (2011). This species readily accepts trap nests (Jensen et al. 2003).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCDFFBE73BD7EF193CB711E.taxon	diagnosis	Diagnosis. The female of M. pugnata can be identified by its parallel-sided tergites (Fig. 6 C), pronounced tooth on the posterior genal margin (Fig. 7 P), and clypeal margin with three tubercles. The genal tooth of the female cannot be mistaken for any other Montana Megachile species. The male of M. pugnata can be identified by its thin and narrowly pointed procoxal spine (Fig. 8 H) and the scoop-shaped dilation of its probasitarsus, which has dark setae along the basal ⅓ of the posterior edge. The males are most similar to M. fidelis (see M. fidelis above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCDFFBE73BD7EF193CB711E.taxon	discussion	Notes. This large, distinctive species is widespread in Montana, although most records are from the west (Fig. 1 AC). The fact that records extend to the southeast border indicates it will be found more broadly with more collecting in the under-sampled eastern part of the state. Photographs, a full morphological description, and notes on the biology of this cavity-nesting species can be found in Sheffield et al. (2011), who report that it is a Helianthus specialist. The voucher for the misidentified specimen (Pearce et al. 2012) is in the MTEC identified as a male M. pugnata (MTEC 57005) (Table 2; Supp. Material 2: Erroneous Records).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCCFFBF73BD7FD093E77687.taxon	diagnosis	Diagnosis. The female of M. rotundata can be identified by its white apical setal bands on S 2 – 6 (Fig. 6 A), white scopal setae on at least the basal half of S 5, lateral, ovate fovea on T 2, and the absence of lateral, ovate fovea on T 3. 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 T 2 and the absence of lateral, ovate fovea on T 3. Males of M. rotundata are most similar to M. apicalis (see M. apicalis above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCCFFBF73BD7FD093E77687.taxon	discussion	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).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCCFFBF73BD7B7490E8731B.taxon	diagnosis	Diagnosis. The female of M. snowi can be identified by its mostly yellow to orange scopal setae on S 6, white to golden appressed setae on T 6, T 6 straight (viewed laterally) (Fig. 7 J), and 4 - toothed mandibles with an angulate basal mandibular tooth, appearing as a weak additional tooth (i. e., 5 - toothed) (Fig. 7 D). The female of M. snowi is most similar to M. mendica (see M. mendica above). The male of M. snowi can be identified by its white apical setal band on T 5 and by the apical margin of T 6 (ventrad the transverse carina), which has submedian teeth that are either closer to each other than to the lateral teeth or all teeth are subequal to each other (Fig. 9 E). Males of M. snowi are most similar to M. mendica (see M. mendica above).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCCFFBF73BD7B7490E8731B.taxon	discussion	Notes. This species is a new state record for Montana. Megachile snowi, a now-recognized species previously recognized as a subspecies of M. mendica, has only been collected from one locality in eastern Montana, a northern extension of its known range (Fig. 1 AF). Illustrations and a full morphological description can be found in Bzdyk (2012).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCCFFB073BD7988938074B4.taxon	diagnosis	Diagnosis. The female of M. subnigra can be identified by its all-black scopal setae on S 2 – 6 and 4 - toothed mandibles with a pointed basal mandibular tooth (Fig. 7 B). The female of M. subnigra is most similar to M. gemula, which has reddish-brown scopal setae on S 2 – 6 and a truncate basal mandibular tooth (Fig. 7 E). For further details on identification issues see Taxonomic Challenges. The male of M. subnigra can be identified by the mostly black pubescence on the mid and hind legs, cream to yellow colored protarsi, and the wide, spatulate procoxal spine (Fig. 8 I) with a short suberect patch of setae at the base.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFCCFFB073BD7988938074B4.taxon	discussion	Notes. Megachile subnigra is known from the southern half of central Montana, in the upper Yellowstone and upper Missouri drainages (Fig. 1 AG). Photographs, a full morphological description, and notes on the biology of this ground-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC3FFB073BD7D65951171E3.taxon	diagnosis	Diagnosis. The female of M. texana can be identified by its 4 - toothed mandibles, which have an even semicircular emargination between the 3 rd and 4 th tooth (Fig. 7 B), and the lateral, erect, black setae on T 2 – 6 (viewed dorsally). The male of M. texana can be identified by the apical margin of T 6 (ventrad the transverse carina), which has submedian teeth that are closer to the lateral teeth than to each other (Fig. 9 E), greater than 50 % black pubescence on the scutum, tergites with significant bands of black pubescence, and vertex of head with greater than 50 % black pubescence. This species is most similar to M. lippiae (see M. lippiae above and Taxonomic Challenges).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC3FFB073BD7D65951171E3.taxon	discussion	Notes. Megachile texana has been recorded mainly east of the divide in Montana (Fig. 1 AH). Photographs, illustrations, full morphological descriptions, and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011) and Bzdyk (2012). Sheffield and Genaro (2013) briefly made a claim of dividing M. texana from Megachile cleomis Cockerell. See Taxonomic Challenges above for a more complete discussion.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC3FFB073BD7B90921A723A.taxon	diagnosis	Diagnosis. The female of M. wheeleri can be identified by its 4 - toothed mandibles with an asymmetrical emargination between the 3 rd and 4 th tooth, emargination deepest closer to 4 th tooth, and the widely spaced punctures on the apical half of T 5, which are separated by 3 – 4 diameters. Females of M. wheeleri are most similar to M. manifesta (see M. manifesta above) and M. nevadensis (see M. nevadensis above and Taxonomic Challenges). The male of M. wheeleri can be identified by its wide and spatulate procoxal spine without a setal patch at the base, the protruding triangular carina on the ventral mesepisternum (viewed ventrally, directly posterior to the procoxal spine), and the quadrate metatarsomeres (viewed laterally) (Fig. 8 G).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC3FFB073BD7B90921A723A.taxon	discussion	Notes. This species occurs in central Montana and the lower elevations of western Montana, west of 109 ° (Fig. 1 AI). This is the only member of Megachiloides besides the rarely seen M. pascoensis that has been found west of the divide. Photographs, a full morphological description, and notes on the biology of this soil-nesting species can be found in Sheffield et al. (2011).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC2FFB273BD797092287334.taxon	discussion	Eight North American species of Megachile are recorded in literature and databases occurring close to or in continuous landscapes with Montana but have not yet been recorded in the state. These species are predicted to possibly occur in Montana and may be uncovered through further faunistic work. Many species on this list (e. g., Megachile wyomingensis, Megachile latita, and Megachile hookeri) are very rarely collected and have not been critically examined since Mitchell, who may have had only one to very few specimens. All need a review as part of a comprehensive revision. Megachile (Xanthosarus) circumcincta (Kirby) is a boreal species ranging from Alaska through British Columbia and Alberta into northern Saskatchewan (Mitchell 1935 b; Sheffield et al. 2011; Sheffield 2021). It has also been recorded from the mountains of Colorado (Mitchell 1935 b; Scott et al. 2011 = Megachile giliae Cockerell). With records both north and south of Montana, this species is predicted to occur widely in Montana. Megachile (Megachiloides) hookeri Cockerell, which Mitchell states may be a color variation of M. nevadensis (Mitchell 1937 a), was collected 200 km away from the Montana border in Pavillion, Wyoming (BBSL 518981). It is also recorded in Lehi, Utah (Mitchell 1937 a), and Colorado (Scott et al. 2011). From the Wyoming record, we predict M. hookeri may be found in the south-central badlands region of Montana near Bridger. Discover Life shows an unvouchered Montana centroid record for Megachile (Sayapis) inimica Cresson (Discover Life 05 May 2021). There is a specimen record near Montana from Moran, Wyoming (AMNH UID 653582), the identification of which was verified by Corey Smith (pers. com., 24 Mar 2021). As this species is also recorded close to the Wasatch Range in Willard, Utah (BBSL 519969), we predict M. inimica may occur in southwest Montana, especially in the Centennial Valley (Beaverhead Co.) and surrounding area. Megachile (Megachiloides) latita Mitchell was recorded in badland habitats in Worland, Wyoming and Maybell, Colorado (Mitchell 1934). As Worland is near the Montana border, we predict this species may occur in south-central Montana in the contiguous xeric area south of Bridger. Megachile (Leptorachis) petulans Cresson has been recorded to occur widely in the eastern, southern, and central U. S. but has fewer western records (Discover Life 01 June 2021, Mitchell 1937 b). As it has been recorded from Jamestown, North Dakota (Mitchell 1937 b), a prairie pothole region, it would possibly be found in the prairie pothole region of northeast Montana near Plentywood and Caldera, approaching the North Dakota and Saskatchewan borders. Megachile (Megachiloides) umatillensis (Mitchell) was recorded from Cornish, Utah, near the Wasatch Range (SEMC 416330, Discover Life, 05 May 2021), in southern British Columbia (Sheffield et al. 2011; Sheffield & Heron 2019), in Santa Clara, Utah, in Roggen, Colorado, and in Washington (Mitchell 1936). With records north, west, and south of Montana, we predict this species is likely to occur at least along the western or southern borders of Montana, but we have not detected it so far. Megachile (Megachiloides) wyomingensis Mitchell was recorded from badlands near Worland, Wyoming (Mitchell 1937 a). It is also recorded from Sweetwater Co., Wyoming (SEMC 498031) and Leota, Utah (BBSL 519311), on Discover Life (01 June 2021). From these records, M. wyomingensis may possibly occur in the same area of south-central Montana, specifically south of Bridger, in the xeric landscape. Further afield, but worth considering, specimens of Megachile (Chelostomoides) subexilis Cockerell are known from Fossil Butte National Monument, Wyoming (USGS _ DRO 314013), Timpanogos Cave National Monument, Utah (AMNH _ BEE 00079322), Provo, Utah (AMNH _ BEE 0007931), and Badlands National Park, South Dakota (USGS _ DRO 246767). This distribution suggests that this species is somewhat likely to occur in the badlands of south-central Montana near Bridger, the Black Hills region of Carter Co., and / or in the southwest corner of the state in or near the Centennial Valley (Beaverhead Co.). Two introduced Eurasian species that may reach Montana. Megachile (Eutricharaea) pusilla Pérez is an invasive species originally from the Mediterranean region (Ghazi-Soltani et al. 2017) that is expanding its range in the U. S., including the west (Discover Life 01 June 2021), with the closest records being in Otero and Yuma Counties of Colorado (Scott et al. 2011) and in Timpanogos, Utah (AMNH _ BEE 00010214). Although not currently known from the state, M. pusilla could feasibly reach Montana as its range expands in the future. One last invasive species to watch for is Megachile (Callomegachile) sculpturalis (Smith). This native of eastern Asia is spreading from the eastern U. S. and now is established in most states east of the Mississippi River (Stevens et al. 2019). The predicted range of this species includes far western Montana with a lower probability along the Yellowstone River Valley (loc. cit.).	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
03C17C29FFC0FFB373BD7CBF924A722B.taxon	discussion	Megachile rotundata, or the alfalfa leafcutting bee, is native to Eurasia and was detected in the U. S. in the 1930 s after being accidentally introduced (Pitts-Singer & Cane 2011). Soon after, it was propagated across the western U. S. for alfalfa seed pollination, being first noted in Montana in 1969 (Gerber & Akre 1969). It is managed for alfalfa seed pollination widely, including in Montana. Today, among managed species, its economic value is second only to honey bees in crop pollination (Pitts-Singer & Cane 2011). Although M. rotundata are usually thought of as managed in agricultural fields, feral populations also exist in the wild, though floral visitation appears to primarily favor Eurasian weeds (Jensen 2003; O’Neill et al. 2010; Pearce et al. 2012). Megachile rotundata accepts a diversity of nest materials and nesting sites (MacIvor & Moore 2013; Sheffield 2017). In the Wolf Mountains of Montana (45.0386 ° N, 107.0307 ° W), a wild nesting aggregation was found in holes in sandstone cliffs far from alfalfa fields (ZAP pers. obs., 2019). Stem nesting behavior in Megachile makes them more likely to be accidentally transported to new regions, as they readily nest in human-made substrates and can be transported in materials like irrigation tubing or drilled holes in wood or metal (Russo 2016; Poulsen & Rasmussen 2020). These introductions could be an issue for native species as one study in California suggested that invasive Megachile could potentially compete with native Megachile for nesting sites (Cane 2003). Megachile (Eutricharaea) apicalis Spinola is an accidentally introduced species that is now established in the U. S. (Cooper 1984; Russo 2016) and found in Montana. This species was first recorded from Montana by Kuhlman and Burrows (2017) in Missoula Co., and we record specimens from 11 counties in Montana dating from 2013 (Fig. 1 C). It is already documented in much of the western U. S., and is associated with an invasive rangeland weed, Centaurea solstitialis L. (Asteraceae) (Barthell et al. 2001; McIver et al. 2009; Sheffield et al. 2011). In Montana, Kuhlman and Burrows (2017) suggest that M. apicalis may be using Centaurea stoebe L. (Asteraceae), a Montana weed that is a relative of C. solstitialis.	en	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): 1-51, DOI: 10.11646/zootaxa.5683.1.1, URL: http://dx.doi.org/10.11646/zootaxa.5360.3.8
