Key to the dark species of the genus Colletes of México

1 Females, with ten flagellomeres; six visible terga............................................................ 2

- Males, with 11 flagellomeres; seven visible terga............................................................ 13

2(1) All terga with no apical bands; if present, the pubescence is golden.............................................. 3

- Apical bands present but never with golden pubescence....................................................... 7

3(2) Distal margin of clypeus straight; integument of posterior surface of propodeum shiny with wide superficial striae and shallow median punctures (propodeum reddish brown in some females from Central America)........... C. rugicollis Friese, 1900

- Distal margin of clypeus notched; posterior surface of propodeum coarse (may be shiny), punctures variable............. 4

4(3) Integument of propodeum shiny with small striae giving it a reticulate appearance; anterior area of propodeal triangle with lon- gitudinal striae reaching median part; T1 with small, sparse, and shallow punctures............. C. isthmicus Swenk, 1930

- Integument of propodeum with irregular and broad striae with no reticulate appearance; propodeal triangle with longitudinal striae not reaching median part; T1 with dense and variably sized punctures....................................... 5

5(4) Clypeus with thin and dense striae (Fig. 24); F1 longer than F2 or F3 (Fig. 23); supraclypeal area with longitudinal thin striae and a few sparse and deep punctures....................................................... C. chiapensis sp. n.

- Clypeus with thick striae; F1 and F3 sub equal; supraclypeal with thin striae and without punctures..................... 6

6(5) Propodeum shiny with irregular striae and without apparent punctures; facial fovea slightly broad in proximal margin of eye................................................................................... C. guatemalensis sp. n.

- Propodeum matte with uniform and shallow punctures between striate; facial fovea distinctly broad in the proximal margin of eye......................................................................... C. panamensis Michener, 1954

7(2) Tegula amberish (Fig. 3); sides of acarinarium on T1 with thin and dense striate....................... C. tzotzilis sp. n.

- Tegula dark brown, never amberish; sides of acarinarium on T1 smooth or punctate never striated...................... 8

8(7) Labrum with lateral depressions and median elevation, notched on proximal margin (Fig. 45); clypeus with striae never reach- ing proximal or distal margins............................................................... C. isabelae sp. n.

- Labrum without lateral depressions and/or notched elevation on basal margin; clypeus with striae reaching proximal and distal margins............................................................................................. 9

9(8) Labrum whithout sulcus dividing median elevation or longitudinal striae (as in Fig. 45) on both sides; anterior margin of scutum without elevations.............................................................................. 10

- Labrum whith median elevation divided by longitudinal sulcus or with longitudinal striae on both sides; scutum with two flat projections near anterior margin (only for C. solari)......................................................... 11

10(9) Terga reddish brown (Fig. 32); malar area four times wider than long; face with small punctures that become denser towards lower paraocular area.................................................................. C. jaliscoensis sp. n.

- Terga black; malar area two and a half times wider than longer; face with uniform puncture density throughout........................................................................................... C. bombiformis Metz, 1910

11(9) Clypeus and malar area longer than wide; discal area of clypeus slightly protuberant in lateral view without central depression (Fig. 53); T2–T5 with slight gold iridescence; apical bands of terga thin and yellowish (Fig. 50)............ C. solari sp. n.

- Clypeus and malar area wider than long; clypeus noticeably protuberant in lateral view with or without central depression; T2– 5 without gold iridescence; terga shiny black without apical bands.............................................. 12

12(11) Terga with small, dense, and shallow punctures with the exception of the marginal zone (Fig. 39)....... C. nigerrima sp. n.

- Terga with sparse punctures including the marginal zone (Fig. 10).................................... C. jobeli sp. n.

13(1) Mesosoma with deep and contiguous punctures; terga with apical bands of whitish hairs............................ 14

- Mesosoma with shallow punctures, dense but no contiguous; all terga without apical bands (except for C. solari)......... 15

14(13) Supraclypeal area with shallow punctures and striae with eroded appearance (Fig. 17)............. C. guatemalensis sp. n.

- Supraclypeal area with deep punctures and smooth, well defined striae....................... C. rugicollis Friese, 1900

15(14) Tegula and wing amberish, wing veins light brown (Figs. 1, 2, 3)................................... C. tzotzilis sp. n.

- Tegula light or dark brown; wing hyaline or with smoky coloration............................................. 16

16(15) Terga with black integument and blue iridescence, mainly on discal area......................................... 17

- Terga with black integument without iridescence, or terga reddish brown with blue iridescence....................... 18

17(16) Facial fovea thin along entire paraocular area; propodeum with broad posterior surface......... C. bombiformis Metz, 1910

- Facial fovea broadened towards upper paraocular area; propodeum triangle with thin posterior surface..... C. isabelae sp. n.

18(16) Eyes strongly emarginate; malar area and clypeus longer than wide (Fig. 53); terga with apical bands yellowish and thin.............................................................................................. C. solari sp. n.

- Eyes slightly emarginate; malar area and clypeus wider than long; apical bands of terga if present never yellowish........ 19

19(18) Terga with marginal zone reddish brown, occasionally amberish; T1–T3 with variably sized punctures on posterior margins..................................................................................................... 20

- Terga with marginal zone black; T1–T3 without punctures on posterior margins (Fig. 39).............. C. nigerrima sp. n.

20(19) Terga with reddish brown integument and blue iridescence; tegula with reddish brown integument, uniformly punctate; scutum with shallow punctures separated by more than a puncture diameter.............................. C. jaliscoensis sp. n.

- Terga with black integument; tegula with dark brown integument and denser punctures on anterior margin (Fig. 11); scutum with dense and deep punctures separated by less than half their diameter............................... C. jobeli sp. n.