Megachile (Chalepochile)

Gonzalez, Victor H., Griswold, Terry & Engel, Michael S., 2018, South American Leaf-Cutter Bees (Genus Megachile) Of The Subgenera Rhyssomegachile And Zonomegachile, With Two New Subgenera (Hymenoptera: Megachilidae), Bulletin of the American Museum of Natural History 2018 (425), pp. 1-73 : 1-73

Chalepochile are unknown)

1. Mandible with interdental laminae (figs. 2, 3C–F), if in second interspace only, then lamina complete (entirely filling interspace), or mandible clearly five-toothed, with Mt 4 and Mt 5 about as apart as Mt 3 and Mt 4 .........2

—Mandible without (fig. 3A) or with scarcely evident interdental laminae as seen in frontal view (fig. 1A), or with incomplete interdental lamina in second interspace only; mandible with less than five teeth, or, if fivetoothed, then upper two teeth (Mt 4 and Mt 5) usually closer than Mt 3 and Mt 4 ............8

2(1). S6 with at least posterior half bare or nearly so, except for subapical row of short setae, behind which is a bare, smooth rim directed posteriorly (fig. 5B).................................3

—S6 with well dispersed scopal setae (fig. 5A), or, if partly bare, then without bare apical rim behind transverse fringe of short setae or (in Argyropile Mitchell ) rim directed upward, or rim narrow and barely recognizable .............. 18

3(2). Mandible five-toothed, a long interdental lamina in second interspace, none elsewhere ................................... Melanosarus Mitchell

—Mandible four-toothed, a well-formed interdental laminae in third interspace ........... 4

4(3). Second interspace distinct (fig. 3E), with interdental laminae usually present; apex of Mt 3 usually acute ....................................... 5

—Second interspace lacking or small, without a distinct interdental lamina; apex of Mt 3 usually truncate .......................................... 7

5(4). Inner angle of mandible truncate, or apical margin of clypeus impressed medially; S6 with distal margin rather narrowly truncate ............................................. Moureapis Raw

—Inner angle of mandible acute or rounded; clypeal margin not deeply impressed medially, slightly medially emarginate to straight and entire; S6 with distal margin broadly truncate or rounded .................................... 6

6(5). Second interspace shorter than third, with small, often inconspicuous interdental lamina; apical margin of clypeus slightly emarginate medially ......... Leptorachis Mitchell (in part) [M. (L.) crotalariae Schwimmer]

—Second interspace about as long as third, with distinct interdental lamina; clypeal margin straight and entire ............................................ ............................. Pseudocentron Mitchell

7(4).Mandible robust, apical tooth more protuberant, much broader than other teeth (fig. 3C); gena usually broader than compound eye in lateral view ....... Acentron Mitchell

—Mandible less robust, apical tooth not much broader than second or third; gena usually narrower than compound eye in lateral view ......................... Leptorachis Mitchell (in part)

8(1). Mandible with a distinct incomplete interdental lamina in second interspace, and no lamina elsewhere, or with scarcely evident interdental laminae in second and third interspaces .................................................. 9

—Mandible without interdental laminae in second and third interspaces ...................... 12

9(8). Body very large and robust (20 × 10 mm); pubescence entirely fulvous (mandible with first interspace small or lacking, second and third narrow and angled, not semicircular, upper tooth truncate; Mexico) ....................... ................................... Grosapis Mitchell

—Body not so large and robust; pubescence usually not entirely fulvous (body pubescence fulvous in M. (Sayapis) palmeri Cresson but all mandibular interspaces distinct, semicircular, and upper tooth acute) ............ 10

10(9). Preoccipital carina distinct behind gena .............. Rhyssomegachile Mitchell (in part)

—Preoccipital margin of gena not carinate ... 11

11(10). T6 straight or nearly so in profile; sterna with incomplete white apical fascia beneath scopa; apex of protibia without a distinct acute spine on outer surface ........................... ................... Chrysosarus Mitchell (in part)

—T6 usually strongly concave in profile; sterna usually without apical fascia beneath scopa; apex of protibia with a distinct acute spine on outer surface .................. Sayapis Titus

12(8). Apex of protibia without distinct acute spine on outer surface ................................ 13

—Apex of protibia with at least one distinct acute spine on outer surface ..................... 14

13(12). T6 distinctly concave in profile, without conspicuous erect pubescence except near base; body pubescence largely white or gray; metasomal sterna without white fasciae beneath scopa (Holarctic) ............................... .............. Megachile Latreille s.str. (in part)

—T6 nearly straight or concave in profile, with abundant erect pubescence; body pubescence of variable color; metasomal sterna with white fasciae beneath scopa absent or broadly interrupted medially (Neotropical) ..................... Chrysosarus Mitchell (in part)

14(12). Body very large and robust (> 18 mm in length); pubescence with large areas of black or fulvous setae; apex of protibia with two or three spines on outer surface (adventive)......15

—Body not so large and robust (~ 15 mm in length); pubescence largely white, not fulvous; apex of protibia with only one acute spine on outer surface ................................ 17

15(14). Apex of protibia with three distinct sharp spines or teeth on outer surface; clypeus with longitudinal elevation, highest at lower clypeal margin ( Jamaica) ................................ .............................. Gronoceras Cockerell

—Apex of protibia with two teeth and spines on outer surface; clypeus unmodified or not modified as above ...................................... 16

16(15). Mandibular carinae minutely roughened, sometimes dull; adductor interspace of inner surface of mandible covered with very small (≤0.2 × OD) appressed setae ........................... ............................... Callomegachile Michener

—Mandibular carinae shining and smooth (at 40 ×); adductor interspace of inner surface of mandible sparsely covered with longer setae (≥0.4 × OD) ............. Pseudomegachile Friese

17(14). Pronotal lobe with asetose transverse lamella hidden among setae; mandible with third interspace narrowly U-shaped and much deeper than others; clypeus with a strong, bifid median process extending down over base of labrum .............................. .................................... Schrottkyapis Mitchell

—Pronotal lobe with transverse, unusually setose ridge, sometimes with shiny low carina; mandible with third interspace not narrower and deeper than others; clypeus unmodified or not modified as above ................................ ........................... Chelostomoides Robertson

18(2). Mandible three-toothed or median tooth weakly divided and mandible thus obscurely four-toothed, with interdental lamina limited to upper interspace (second if mandible is tridentate, third if mandible is quadridentate) (Nearctic) ................................................. ................... Megachiloides Mitchell (in part)

—Mandible four- or five-toothed, with interdental laminae in third and usually second interspaces ................................................ 19

19(18). Mandible robust, apical tooth more protuberant, much broader than other teeth ...... 20

—Mandible less robust, apical tooth not much broader than second or third .................. 22

20(19). S6 with apical rim directed upward beyond fringe of setae, this rim conspicuous if tergum and sternum are spread apart; middle tarsomeres with conspicuously narrow bases, if anterodistal margin projected, projection slender and elongate ..................... ....................................... Argyropile Mitchell

—S6 without apical rim directed upward beyond fringe of setae, or, if apical margin is swollen as in M. (Xanthosarus) fortis Cresson , bases and anterodistal projections of middle tarsomeres broad and acutely angulate, not elongate ...... 21

21(20). T6 straight in profile; mandible with second tooth often rounded or obtuse; usually no interdental lamina in second interspace .................... Megachiloides Mitchell (in part)

—T6 straight or concave in profile; mandible with second tooth usually acute; often with small incomplete interdental lamina in second interspace .................................................. ................. Xanthosarus Robertson (in part)

22(19). Mesosomal venter, including leg bases and S2, with dense covering of fine, plumose setae, sharply differentiated from other scopal setae .......................... Ptilosarus Mitchell

—Mesosomal venter and leg bases with ordinary setae, scopal setae all unbranched ............. 23

23(22). Metasomal sterna with entire and conspicuous white apical fasciae beneath scopa ......................................................................... 24

—Metasomal sterna with white apical fasciae absent or broadly interrupted medially, except on S5 ............................................... 25

24(23). Mandible four-toothed, no interdental lamina in second interspace (adventive, North America, Antilles, Chile, and Argentina) ........................ Eutricharaea Thomson

—Mandible with fourth tooth emarginate, thus five-toothed, second interspace with conspicuous but incomplete interdental lamina (South America) ....... Trichurochile Mitchell

25(23). Mandible four-toothed, upper tooth acute or right-angular ........................................... 26

—Mandible four- or five-toothed but if fourtoothed, then upper tooth rounded, truncate, or incised (sometimes only minutely) and thus approaching five-toothed condition ................................................................ 29

26(25). Metasoma broadly conical, T3 narrower than T1 or T2 (Neotropical) .......................... ..................... Tylomegachile Moure (in part)

—Metasoma more ovoid, T3 as broad as T1 ... 27

27(26). Scopa black; body usually covered with long, dense setae sometimes obscuring integument and not forming pale apical tergal fasciae, producing a Bombus -like aspect, or, if rather ordinary looking species, then clypeus and supraclypeal area flat and dull, with abundant erect, short, and partly hooked setae (primarily Andean) ................... ................. Dasymegachile Mitchell (in part)

—Scopa brownish, yellowish or white except on S6; body not densely covered with long, dense setae; clypeus and supraclypeal area not flat, shiny, and without hooked setae ............ 28

28(27). Interdental laminae in both second and third interspaces incomplete, that of second only very slightly depressed below level of interspace margin; T6 straight in profile (South America) ... Zonomegachile Mitchell

—Third interspace with complete interdental lamina; second interspace with incomplete interdental lamina, distinctly below level of interspace margin; T6 straight or preapically concave in profile (Nearctic) .......................... .................................. Litomegachile Mitchell

29(25). Scopa black; body usually covered with long, dense setae sometimes obscuring integument and not forming pale apical tergal fasciae, producing a Bombus -like aspect, or, if rather ordinary looking species, then clypeus and supraclypeal area flat and dull, with abundant erect, short, and partly hooked setae (primarily Andean) .................... ................ Dasymegachile Mitchell (in part)

—Scopa variable in color, black with brightly reddish setae on S3–S5, brownish or white, except on S6; body usually not densely covered with long, dense setae; clypeus and supraclypeal area not flat, shiny, and without hooked setae ............................................ 30

30(29). Mandible clearly five-toothed, distance between upper two teeth not or only slightly less than distance between other pairs of teeth (Holarctic) ............................................... ........... Megachile Latreille s.str. (in part)

—Mandible four-toothed but upper tooth rounded, truncate, or itself bidentate (sometimes minutely), mandible thus five-toothed but distance between upper two teeth short compared to distances between other pairs of teeth ..................................................... 31

31(30). Metasoma distinctly conical, T1 and T2 broader than T3 ........................................... 32

—Metasoma more ovoid, T3 as broad as or broader than T1 ........................................... 33

32(31). Metasomal sterna with widely interrupted apical white fasciae beneath scopa; posterior apical angle of metabasitarsus (metatarsomere 1) slightly produced, that of metatarsomere 2 more conspicuously so (preoccipital margin of gena usually with distinct carina or sharp border) ................ Austromegachile Mitchell (in part) [M. (A.) exaltata Smith ]

—Metasomal sterna not at all fasciate; metatarsomeres 1 and 2 not or little produced apically ............... Tylomegachile Moure (in part)

33(31). Median area of clypeus somewhat elevated and strongly flattened, sloping away on each side (apical margin of clypeus medially emarginate) ................................................ ................. Austromegachile Mitchell (in part)

—Clypeus broadly convex or nearly flat, neither elevated nor flat medially .......................... 34

34(33). Pubescence of T6 conspicuous, with many erect setae as seen in profile ............ 35

—Pubescence of T6 largely decumbent, with few or no erect setae visible in profile ............ 36

35(34). Lateral ocellus considerably nearer to posterior margin of vertex than to compound eye .................. Cressoniella Mitchell

—Lateral ocellus usually as near as or nearer to compound eye than to posterior margin of vertex ........ Xanthosarus Robertson (in part)

36(34). Preoccipital carina distinct behind gena (also along vertex in M. guayaqui Schrottky ); interdental laminae of mandible obsolete, hidden behind interspace margin (fig. 1); ocelloccipital distance greater than ocellocular distance ........................................................ .............. Rhyssomegachile Mitchell (in part)

—Preoccipital margin of gena usually not carinate, but if so, then interdental laminae of mandibles wellformed and easily recognized in frontal view; ocelloccipital distance shorter than ocellocular distance .............. 37

37(36). Mesosoma and metasoma densely and minutely punctate throughout, largely covered with appressed or suberect tomentum; integument of metanotum largely visible among setae; apical terga densely covered by appressed, yellowish tomentum and thus contrasting with color of preceding terga .... ............................... Ptilosaroides Mitchell

—Mesosoma and metasoma with punctures distinctly separated, surface not tomentose to any considerable degree; integument of metanotum hidden by dense tomentum; apical terga without appressed, yellowish tomentum, with pubescence as on preceding terga ............................. Neochelynia Schrottky