Megachile, Latrielle

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 : 17-27

Key to the Megachile Species of Montana

This key was written based on previous works by Mitchell (1924, 1926a, 1927a, 1927 b, 1934, 1935a, 1935 b, 1936, 1937a, 1937 b, 1937c, 1937d, 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.

Abbreviations used in key

S 1– S 6: Sternites on the ventral surface of the metasoma.

T 1– T 6: Tergites on the dorsal surface of the metasoma.

Key to Megachile species of Montana: female specimens (i.e., 10 flagellomeres, 6 tergites)

1 Metasomal sternites with white apical setal bands between scopal setae ( Fig. 6A ); T2 with lateral, ovate fovea........... 2

- Metasomal sternites without white apical setal bands between scopal setae; T2 without lateral, ovate fovea.............. 3

2 S5 scopal setae all black; clypeal margin with small median tubercle ( Fig. 6D ); T3 with lateral, ovate fovea................................................................................. Megachile (Eutricharaea) apicalis Spinola

- S5 scopal setae white, sometimes apical half with black setae; clypeal margin without median tubercle, essentially straight; T3 without lateral, ovate fovea........................................ Megachile (Eutricharaea) rotundata (Fabricius)

[Note: Megachile (Eutricharaea) pusilla Pérez also keys out at 2’. This species has not been recorded from Montana but is an introduced species that could potentially occur in the state. Megachile pusilla has black setae laterally on T5–6 at most, while M. rotundata has black setae laterally on T2–6.]

3 Metasoma rounded in dorsal view, T2–3 widest, then narrowing from T4–6 ( Fig. 6B )............................... 4

- Metasoma subparallel in dorsal view, T2–4 subequal in width ( Fig. 6C )......................................... 32

4 Tergites without white apical setal bands; T1–2 covered in pale yellow to white pubescence contrasting entirely dark pubescence on T3–5............................................................................................. 5

- Most tergites with white apical setal bands; T1–2 sometimes with pale pubescence, but T3–5 without entirely black pubescence.......................................................................................... 7

5 S2–6 scopal setae orange; T6 usually with pale appressed setae............. Megachile (Xanthosarus) melanophaea Smith

[Note: Megachile (Xanthosarus) circumcincata (Kirby) also keys out at 5. This species has not been recorded from Montana but could potentially occur in the state. Megachile circumcincta has entirely pale pubescence on the ventral mesosoma and coxae, whereas Megachile melanophaea has dark pubescence on the ventral mesosoma and coxae.]

- S 2–6 scopal setae reddish-brown to black; T 6 usually with dark appressed setae.................................... 6

6 Basal mandibular tooth truncate ( Fig. 7E ); mandible from lateral view square basally, with parallel sides for a distance as long as wide, then tapering apically ( Fig. 6J ); S 2–6 scopal setae reddish-brown to black.................................................................................................... Megachile (Xanthosarus) gemula Cresson

- Basal mandibular tooth pointed ( Fig. 7B ); mandible from lateral view gradually tapering in width towards apex ( Fig. 6I ); S 2–6 scopal setae entirely black...................................... Megachile (Megachiloides) subnigra Cresson (part)

7 S 2–4 scopal setae entirely black.................................. Megachile (Megachiloides) subnigra Cresson (part)

[Note: There is a pale form of M. subnigra that has not been recorded from Montana but could potentially occur in the state. This form has all white scopal setae, T 6 straight in lateral profile, and 4-toothed mandibles without basal tooth with an angulation appearing as a weak additional tooth (i.e., appearing 5-toothed).]

[Note: Rare, melanistic forms of Megachile (Megachiloides) anograe Cockerell ( S 2–6 scopal setae black) also key out at 7 but have 3-toothed mandibles (4-toothed in M. subnigra ). This form has not been recorded from Montana.]

- S 2–4 scopal setae usually white, yellow, or orange........................................................... 8

8 Mandible 3-toothed ( Fig. 7A )............................................................................ 9

- Mandible 4- ( Figs. 7B–E ) or 5-toothed ( Figs. 7F–H )........................................................ 10

9 T 6 smooth and shiny, with punctures 3–5 diameters apart................. Megachile (Megachiloides) anograe Cockerell

- T 6 pitted and dull, with punctures ≤ 1 diameter apart.................... Megachile (Megachiloides) pascoensis Mitchell

10 S 6 scopal setae mostly (greater than 75%) pale, ivory to orange (can have black setae apically on S 6) ( M. mendica can approach ca. 50% black setae apically)........................................................................... 11

- S 6 scopal setae mostly (greater than 75%) dark, brown to black ( M. casadae and M. texana can approach ca. 50% pale setae basally)............................................................................................ 22

[Note: Setal coloration can be an unreliable character, as it can change or fade with time. Coloration can also vary intraspecifically, and specimens with questionable coloration can be keyed out in both directions.]

11 Mandibles 5-toothed, with deepest emargination between tips of 3 rd and 4 th tooth, emargination strongly angled towards 4 th tooth ( Fig. 7F )........................................................................................... 12

- Mandibles 4- or 5-toothed, with emarginations between all teeth similar in depth ( Figs. 7B–E, G–H ).................. 13

12 T 3–5 with apical setal bands consistently wide, as wide medially as laterally; T 1–2 usually covered in white pubescence; T 6 with appressed pale setae............................................ Megachile (Xanthosarus) dentitarsus Sladen

- T 3–5 with apical setal bands inconsistent in width, wider laterally than medially, often incomplete; T 1–2 usually covered in yellow pubescence; T 6 with appressed yellow to orange setae............................................................................... Megachile (Xanthosarus) latimanus Say and Megachile (Xanthosarus) perihirta Cockerell

[Note: The females of M. latimanus and M. perihirta cannot be reliably separated in Montana based on morphology. See Taxonomic Challenges in results above.]

13 Basal mandibular tooth truncate ( Fig. 7E ); T 6 setae dark brown to black........... Megachile (Xanthosarus) frigida Smith

- Basal mandibular tooth rounded or pointed ( Fig. 7B–D, G–H ); T 6 setae color variable............................. 14

14 Mandibles without cutting edge ventrad the tooth plane ( Fig. 7H ); mandible surface with elevated ridge running diagonally from apex of 2 nd tooth to the dorsal point of mandibular attachment ( Fig. 7H )..... Megachile (Megachile) montivaga Cresson

- Mandibles with cutting edge ventrad the tooth plane, sometimes only present as small, angled edge ( Figs. 7B–G ); mandible surface without elevated ridge.......................................................................... 15

15 Mandibles 4-toothed (sometimes basal tooth with angulation appearing as a weak additional tooth [i.e., appearing 5-toothed]) ( Figs. 7B, 7D )....................................................................................... 16

- Mandibles 5-toothed ( Fig. 7G ).......................................................................... 20

16 Clypeal margin with two broadly incurved emarginations ( Fig. 6E ); tarsi and basitarsus reddish brown, contrasting black tibia.................................................................... Megachile (Sayapis) mellitarsis Cresson

- Clypeal margin without two broad emarginations; tarsi and basitarsus brown to black, not contrasting tibia............. 17

17 S 6 upcurved at the tip, extending beyond T 6 ( Fig. 7L ); T 6 straight in lateral profile with pale, velvety, appressed setae ( Fig. 7L )................................................................. Megachile (Argyropile) parallela Smith

- S 6 not upcurved or extending beyond T 6 ( Fig. 7I–K, M–N )................................................... 18

18 T 6 convex basally and concave apically in a “pinched shape” in lateral profile ( Fig. 7K ); mandibles with 4 distinct teeth ( Fig. 7B )................................................................... Megachile (Litomegachile) brevis Say

- T 6 straight in lateral profile ( Fig. 7J ); mandibles 4-toothed, basal tooth with angulation appearing as a weak additional tooth [i.e., appearing 5-toothed]............................................................................. 19

19 T 6 with pale appressed setae........................................... Megachile (Litomegachile) snowi Mitchell

- T 6 with brown appressed setae........................................ Megachile (Litomegachile) mendica Cresson

20 Body size 17–20 mm long; clypeus shiny and sparsely punctate medially (punctures 1–3 diameters apart); clypeal margin with four prominent tubercles.............................................. Megachile (Megachile) inermis Provancher

- Body size 9–12 mm long; clypeus densely punctate medially (punctures ≤ 1 diameter apart); clypeal margin irregular, without prominent tubercles.................................................................................. 21

21 T 6 with black setae.............................................. Megachile (Megachile) centuncularis (Linnaeus)

- T 6 with golden setae.................................................... Megachile (Megachile) relativa Cresson

22 T 2 in dorsal view with lateral, erect black setae............................................................ 23

- T 2 in dorsal view without lateral, erect black setae.......................................................... 24

23 T 3–5 strongly concave medially between surrounding apical and basal grooves, when viewed from lateral profile ( Fig. 7O ); ocellocular distance shorter than ocelloccipital distance ( Fig. 8J )........... Megachile (Megachiloides) dakotensis Mitchell

- T 3–5 flat to slightly concave medially, with no prominent apical or basal grooves; ocellocular distance longer than ocelloccipital distance ( Fig. 8L ).................................................... Megachile (Litomegachile) texana Cresson

24 Clypeus shiny and sparsely punctate medially (punctures 2–3 diameters apart), becoming more densely punctate laterally.................................................................. Megachile (Megachiloides) casadae Cockerell

- Clypeus with dense punctation medially and laterally (punctures ≤ 1 diameter apart)............................... 25

25 Mandibles 5-toothed ( Fig. 7G ) OR mandibles 4-toothed, basal tooth with angulation appearing as a weak additional tooth (i.e., appearing 5-toothed) ( Fig. 7D ).......................................................................... 26

- Mandibles distinctly 4-toothed ( Figs. 7B–C )............................................................... 27

26 S 5 scopal setae black, at least apically; mandibles 5-toothed ( Fig. 7G )......... Megachile (Megachile) lapponica Thomson

- S 5 scopal setae white; mandibles 4-toothed with basal mandiblular tooth angulate, appearing as a weak additional tooth (i.e., 5-toothed) ( Fig. 7D )................................................. Megachile (Litomegachile) gentilis Cresson

27 Mandibles with asymmetrical emargination between tips of 3 rd and 4 th tooth, emargination deepest closer to 4 th tooth ( Fig. 7C ) AND mandible from lateral view gradually tapering in width towards apex ( Fig. 6I )............................... 28

- Mandibles with semicircular, symmetrical emargination between tips of 3 rd and 4 th tooth ( Fig. 7B ) AND mandible from lateral view square basally, with sides parallel for approximately ⅓ the length of mandible, then tapering apically ( Fig. 6K )..... 30

28 T 5 with punctures 2–4 diameters apart medially, surface polished and shiny... Megachile (Megachiloides) wheeleri Mitchell

- T 5 with punctures ≤ 1 diameter apart medially, surface matte to shiny........................................... 29

29 S 5 scopal setae all white; area directly posterior of scutum center with variable punctation 1–2 diameters apart.......................................................................... Megachile (Megachiloides) nevadensis Cresson

- S 5 scopal setae at least partly black; area directly posterior of scutum center with consistently spaced punctures almost touching........................................................ Megachile (Megachiloides) manifesta Cresson

30 T 6 strongly convex basally and concave apically in a “pinched shape” in lateral profile ( Fig. 7K ).................................................................................. Megachile (Litomegachile) onobrychidis Cockerell

- T 6 concave apically in lateral profile ( Figs. 7M–N )......................................................... 31

31 T 6 with suberect pale setae and erect black setae; T 6 concave apically in lateral profile ( Fig. 7N ); apical margin of clypeus with short median carina 2 times as long as diameter of median ocellus ( Fig. 6G ).... Megachile (Litomegachile) lippiae Cockerell

- T 6 with suberect and erect brown to black setae (sometimes with suberect pale setae in small patches laterally); T 6 slightly to moderately concave apically in lateral profile ( Fig. 7M ); apical margin of clypeus with long transverse carina 4 times as long as diameter of median ocellus ( Fig. 6H ).............................. Megachile (Litomegachile) coquilletti Cockerell

32 Genal margin with pronounced tooth posteriorly ( Fig. 7P ); clypeal margin with three tubercles.................................................................................................. Megachile (Sayapis) pugnata Say

- Genal margin without tooth posteriorly; clypeal margin variable............................................... 33

33 Mandibles without cutting edge ventrad the 2 nd and 3 rd tooth.................................................. 34

- Mandibles with cutting edge ventrad the 2 nd and 3 rd tooth..................................................... 35

34 In fresh specimens (as judged by a completely intact apical wing margin), T 5 white apical setal band mostly complete medially, similar in width and density to T 1–4 apical setal bands, individual setae thick and plumose; in all specimens, vertex of head with small and dense punctation (ca. 8–10 punctures between lateral ocelli and posterior margin of vertex); scutum and scutellum with similar punctation (close and evenly spaced); occipital suture smooth and shiny, impunctate................................................................................... Megachile (Chelostomoides) angelarum Cockerell

- In fresh specimens (as judged by a completely intact apical wing margin), T 5 white apical setal band incomplete medially, narrower and less dense than T 1–4 apical setal bands, individual setae thinner and less plumose; in all specimens, vertex of head with large, sparse punctation (ca. 4–6 punctures between lateral ocelli and posterior margin of vertex); scutum punctation close and evenly spaced compared to scutellum punctation, which is irregular and inconsistent; occipital suture with a line of punctures appearing as a slight carina........................... Megachile (Chelostomoides) campanulae (Robertson)

[Note: Megachile (Callomegachile) sculpturalis Smith keys out at 34’. This species has not been recorded from Montana but could potentially occur in the state. Megachile sculpturalis has a large body size (21–25 mm long), contrasting the much smaller body sizes of M. angelarum (10–11 mm long) and M. campanulae (10–12 mm long). Megachile sculpturalis also has yellow pubescence on T 1 with a white apical setal band and black apical setal bands on T 2–5, whereas M. angelarum and M. campanulae have white apical setal bands on T 2–5.

35 Clypeal margin with two broadly incurved emarginations ( Fig. 6E ).......... Megachile (Sayapis) mellitarsis Cresson (part)

[Note: Megachile (Sayapis) inimica Cresson also keys out at 35. This species has not been recorded from Montana but could potentially occur in the state. Megachile inimica has all red or all black legs, while M. mellitarsis has red tarsi contrasting with the black tibia.]

- Clypeal margin with two prominent, wide, lateral tubercles (at least as long as wide), surrounding median triangular tubercle ( Fig. 6F )................................................................ Megachile (Sayapis) fidelis Cresson

Key to Megachile species of Montana: male specimens (i.e., 11 flagellomeres, 7 tergites)

1 Probasitarsus narrow, not excavated ventrally ( Fig. 8A ), often brown to black..................................... 2

- Probasitarsus usually widely expanded, excavated ventrally, ( Fig. 8B ), often white to yellow (except M. gemula which has an excavated, but narrow, dark brown to black probasitarsus).................................................... 19

2 T6 (anterior to the transverse carina, Fig. 9C–D ) with tomentose, pale setae....................................... 3

- T6 (anterior to the transverse carina) bare or with sparse setae................................................ 12

3 T2 with lateral, ovate fovea............................................................................. 4

- T2 without lateral, ovate fovea........................................................................... 5

4 T3 with lateral, ovate fovea............................................ Megachile (Eutricharaea) apicalis Spinola

- T3 without lateral, ovate fovea...................................... Megachile (Eutricharaea) rotundata (Fabricius)

[Note: Megachile (Eutricharaea) pusilla also keys out at 4’. This species has not been recorded from Montana but is an introduced species that could potentially occur in the state. Megachile pusilla has a genal tooth posterior to the ventrad point of mandibular attachment that is longer than wide, whereas M. rotundata has a genal tooth that is as long as wide.]

5 T5 with white apical setal band, sometimes in depressed apical groove (sometimes reduced to lateral sides, as in M. coquilletti ).......................................................................................... 6

- T5 without white apical setal band (may have some setae laterally)............................................. 11

6 T6 transverse carina deeply emarginate medially ( Fig. 9A ).................................................... 7

- T6 transverse carina weakly emarginate, often appearing as a continuous jagged edge ( Fig. 9B ).............................................................................................. Megachile (Litomegachile) brevis Say

7 Mandible 4-toothed; apical margin of T6 (ventrad the transverse carina) with two pairs of prominent teeth laterally ( Fig. 9C )..................................................................... Megachile (Argyropile) parallela Smith

- Mandible 3-toothed; apical margin of T6 (ventrad the transverse carina) with two pairs of small teeth laterally ( Fig. 9D ).... 8

8 Protarsomeres 2–4 light to dark yellow............................... Megachile (Litomegachile) coquilletti Cockerell

- Protarsomeres 2–4 brown to black........................................................................ 9

9 Apical margin of T6 (ventrad the transverse carina) with submedian teeth closer to each other than to lateral teeth ( Fig. 9E ) or distances subequal................................................... Megachile (Litomegachile) snowi Mitchell

- Apical margin of T6 (ventrad the transverse carina) with submedian teeth closer to lateral teeth than to each other ( Fig. 9F ).................................................................................................... 10

10 Scutum with greater than 50% black pubescence (viewed laterally); tergites with significant bands of black pubescence (viewed laterally); vertex of head with greater than 50% black pubescence.............. Megachile (Litomegachile) texana Cresson

- Scutum with less than 25% black pubescence (viewed laterally); tergites with mostly white pubescence (viewed laterally); vertex of head with mostly white pubescence............................ Megachile (Litomegachile) lippiae Cockerell

11 T 4–5 somewhat dull, with punctures ca. 1 diameter apart.................... Megachile (Litomegachile) gentilis Cresson

- T 4–5 polished and shiny, with punctures 2–4 diameters apart................ Megachile (Litomegachile) mendica Cresson

12 S 4 not visible, retracted............................................................................... 13

- S 4 visible.......................................................................................... 14

13 Vertex of head with large, sparse punctation (ca. 4 punctures between lateral ocelli and posterior margin of vertex); small procoxal spine present but obscured by dense, plumose setae....... Megachile (Chelostomoides) campanulae (Robertson)

- Vertex of head with small and dense punctation (ca. 9 punctures between lateral ocelli and posterior margin of vertex); small procoxal spine visible amidst surrounding short setae................ Megachile (Chelostomoides) angelarum Cockerell

14 Procoxal spine present, may be reduced to a small nub and covered with small tuft of dense orange setae.............. 15

- Procoxal spine absent................................................................................ 18

15 Procoxal spine prominent, longer than wide............................................................... 16

- Procoxal spine nub-like, wider than long and covered with small tuft of dense orange setae......................... 17

16 Ocelloccipital distance greater than ocellocular distance ( Fig. 8J ); T 2–4 strongly depressed basally and apically ( Fig. 10D )................................................................ Megachile (Megachiloides) dakotensis Mitchell

- Ocelloccipital distance less than ocellocular distance ( Fig. 8L ); T 2–4 moderately depressed basally but not depressed apically ( Fig. 10E )................................................... Megachile (Litomegachile) onobrychidis Cockerell

17 Mandibular teeth unevenly spaced, 2 nd tooth closer to apical tooth; ocelloccipital distance longer than ocellocular distance ( Fig. 8J ); body size 11–16 mm long......................................... Megachile (Megachile) inermis Provancher

- Mandibular teeth evenly spaced from one another; ocelloccipital distance approximately subequal to ( Fig. 8K ) or shorter than (8L) ocellocular distance; body size 9–11mm long......................... Megachile (Megachile) montivaga Cresson

18 Clypeal margin with small triangular median tubercle..................................................................................... Megachile (Megachile) lapponica Thomson and Megachile (Megachile) relativa Cresson

[Note: The males of Montana M. lapponica and M. relativa cannot be reliably separated based on morphology. See Taxonomic Challenges in results above.]

- Clypeal margin without median tubercle............................ Megachile (Megachile) centuncularis (Linnaeus)

19 Mesobasitarsus with smooth, glabrous protuberance ventrally ( Figs. 8C–D ); mesotibia without apical spur ( Figs. 8C–D ); mesofemur widely enlarged, at least 2 times as wide as mesotibia.............................................. 20

- Mesobasitarsus without protuberance ventrally ( Fig. 8E ); mesotibia with apical spur ( Fig. 8E ); mesofemur about 1.5 times as wide as mesotibia................................................................................... 22

20 Ventral mesepisternum (from ventral view of mesosoma, directly anterior to mesocoxa) with small spine................................................................................ Megachile (Xanthosarus) dentitarsus Sladen

- Ventral mesepisternum (from ventral view of mesosoma, directly anterior to mesocoxa) with smooth, spineless carina.... 21

21 Mesobasitarsus from anterior view with narrowly rounded, ventral protuberance basally ( Fig. 8D ); ventral side of mesofemur smooth and convexly rounded....................................... Megachile (Xanthosarus) perihirta Cockerell

- Mesobasitarsus from anterior view with wide, rounded, ventral protuberance basally ( Fig. 8C ); ventral side of mesofemur widely depressed..................................................... Megachile (Xanthosarus) latimanus Say

22 Mandibles 4-toothed................................................................................. 23

- Mandibles 3-toothed................................................................................. 25

23 Profemur with two brown stripes ventrally.................................. Megachile (Xanthosarus) frigida Smith

- Profemur without two brown stripes ventrally (often one stripe occurs on M. circumcincta )......................... 24

24 Dorsal face of protibia with posterior angle acute, apex entirely dark........... Megachile (Xanthosarus) gemula Cresson

[Note: Megachile (Xanthosarus) circumcincta (Kirby) also keys out at 24. This species has not been recorded from Montana but could potentially occur in the state. Megachile circumcincta has a white apical setal band on T 5 (absent in M. gemula ) and often has one brown stripe on the ventral profemur. The dorsal face of the protibia of M. circumcincta has an acute posterior angle as in M. gemula , but the apex is yellow, whereas the apex of the protibia of M. gemula is dark brown to black.]

- Dorsal face of protibia with posterior angle rounded and spatulate, apex entirely pale............................................................................................... Megachile (Xanthosarus) melanophaea Smith

25 Procoxal spine thin and narrowly pointed ( Fig. 8H )......................................................... 26

- Procoxal spine wide and spatulate ( Fig. 8I )............................................................... 28

26 Protarsi distinctly yellow; front basitarsus with elongated apical dilation reaching apex of 3 rd tarsomere.................................................................................... Megachile (Sayapis) mellitarsis Cresson

- Protarsi white or pale yellow to dark brown; front basitarsus with apical dilation not reaching 3 rd tarsomere............ 27

27 Probasitarsus along basal ⅓ of posterior edge of scoop-shaped dilation with dark setae.... Megachile (Sayapis) pugnata Say

- Probasitarsus along entire posterior edge of scoop-shaped dilation with dark setae..... Megachile (Sayapis) fidelis Cresson

[Note: Megachile (Sayapis) inimica Cresson also keys out at 27’. This species has not been recorded from Montana but could potentially occur in the state. Megachile inimica has a patch of short, suberect setae at the base of the procoxal spine (setae shorter than flagellomere 1), whereas M. fidelis has a few long, erect setae (setae longer than flagellomere 1) at the base of the procoxal spine.]

28 Genal margin directly posterior to the ventral mandibular attachment with tooth as-long-as or longer-than-wide (the prolegs may need to be repositioned to see this character) ( Fig. 10H )................................................. 29

- Genal margin directly posterior to the ventral mandibular attachment without obvious tooth, often with a tuft of setae ( Fig. 10I ).............................................................................................. 31

29 Procoxal spine with short, suberect setae in patch at base............... Megachile (Megachiloides) nevadensis Cresson

- Procoxal spine without patch of setae at base.............................................................. 30

30 Ventral mesepisternum (from ventral view of mesosoma, directly posterior to the procoxal spine) with smooth, rounded carina, not protruding; metatarsomeres triangular from lateral view ( Fig. 8F )....... Megachile (Megachiloides) manifesta Cresson

- Ventral mesepisternum (from ventral view of mesosoma, directly posterior to the procoxal spine) with protruding triangular carina; metatarsomeres quadrate from lateral view ( Fig. 8G )............... Megachile (Megachiloides) wheeleri Mitchell

31 Pubescence on meso- and metalegs mostly black........................ Megachile (Megachiloides) subnigra Cresson

- Pubescence on meso- and metalegs mostly pale............................................................ 32

32 Clypeal margin emarginate medially and laterally ( Figs. 10A–B ).............................................. 33

- Clypeal margin mostly straight, with slight emargination medially ( Fig. 10C )...................................................................................................... Megachile (Megachiloides) casadae Cockerell

33 Clypeal margin with deep U-shaped median emargination (as deep as wide) ( Fig. 10A ); S 5 narrowly rimmed apicomedially with dark brown setae ( Fig. 10F ); metafemur with hint of pale fovea dorsally.................................................................................................... Megachile (Megachiloides) pascoensis Mitchell

- Clypeal margin with wide, shallow median emargination (2–3 times as wide as deep) ( Fig. 10B ); S 5 with black apicomedial setal patch ( Fig. 10G ); metafemur with distinct, elongate, brown fovea dorsally.................................................................................................... Megachile (Megachiloides) anograe Cockerell

[Note: Megachile (Callomegachile) sculpturalis (Smith) also keys out at 33’. This species has not been recorded from Montana but is an introduced species that could potentially occur in the state. Megachile sculpturalis has extremely large, unevenly-spaced punctures on T 2–3, T 2–4 basally depressed, T 2–5 without white apical setal bands, a carinate genal margin, a large body size (> 20 mm long), and lacks dorsal fovea on the metafemur as seen in M. anograe . Megachile anograe has white apical setal bands on T 1–4, lacks a carinate genal margin, and is smaller (10–11 mm long) than M. sculpturalis .]

Figures

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.

FIGURE 8. Male Megachile characters. (A) Probasitarsus not expanded or excavated ventrally, (B) Probasitarsus widely expanded and excavated ventrally, (C–E) Anterior view of mesobasitarsus and mesotibia, (F) Lateral view of triangular metatarsomeres on M. manifesta, (G) Lateral view of quadrate metatarsomeres on M. wheeleri, (H) Ventral view of procoxal spine, longer than wide, (I) Ventral view of procoxal spine, wide and spatulate, (J–L) Dorsal view of vertex of head: (J) Ocelloccipital distance longer than ocellocular distance, (K) Ocelloccipital distance equal to ocellocular distance, and (L) Ocelloccipital distance shorter than ocellocular distance.

FIGURE 9. Male Megachile T6 characters. (A–B) Transverse carina, (C) Apical margin with two pairs of prominent teeth on M. parallela, (D) Apical margin with two pairs of small teeth, (E) Apical margin (ventrad the transverse carina) with submedian teeth closer to each other than to lateral teeth, and (F) Apical margin (ventrad to the transverse carina) with submedian teeth closer to lateral teeth than to each other.

FIGURE 10. Male Megachile characters. (A–C) Anterior view of clypeus: (A) M. pascoensis, (B) M. anograe, (C) M. casadae, (D) Lateral view of tergites on M. dakotensis, (E) Lateral view of tergites on M. onobrychidis, (F) Ventral view of sternites without apicomedial setal patch on S5, (G) Ventral view of sternites of M. anograe with apicomedial setal patch on S5, (H) Lateral view of genal margin with tooth at least as long as wide, and (I) Lateral view of genal margin without obvious tooth.