Key to known females of Lasioglossum (Dialictus) from the Yucatán Peninsula

1. Propodeum dorsolateral slope smooth, with no oblique carina (Fig. 22A–B) ................................. 2

– Propodeum dorsolateral slope with an oblique carina (Fig. 22C) .................................................... 5

2. Metapostnotum smooth with weak rugae covering less than half its length (Fig. 22A); mesonotum and mesepisternum shiny due to weak or absent microsculpture (Fig. 23A); metasoma black to brown and without appressed tomentum .......................................................................................... 3

– Metapostnotum with strong rugae covering half or more its length (Fig. 22B); mesonotum and mesepisternum dull due to very strong microsculpture (Fig. 23B); metasoma orange to reddish brown and with some sparse appressed tomentum on T2–T4 ............................................................ .................................................................................................. L. meteorum Gardner & Gibbs, 2020

3. Clypeus apicolateral margins parallel with distinct, acute teeth (Fig. 24A); hind legs and tarsi of other legs light brown; abdomen dark brown, margin of segment testaceos; metanotum with abundant short plumose setae (Fig. 23A) ................................................................. L. exiguum (Smith, 1879)

– Clypeus apicolateral margins strongly convergent with indistinct, rounded knobs (Fig. 24B); hind legs dark brown or black, tarsi sometimes lighter; abdomen piceous, margin of segment not testaceous; metanotum with short plumose setae very sparse or absent (as in Fig. 23B) ................ 4

4. Mesoscutum between parapsidal lines and mesoscutellum sparsely punctate (i = 2–4 pd); face broader than long ......................................................................................... L. tropicior (Ellis, 1914)

– Mesoscutum between parapsidal lines and mesoscutellum moderately densely punctate (i = 1–2 pd); face about as long as broad or slightly longer ............................................. L. deceptor (Ellis, 1914)

5. Tegula ovoid and relatively small, clearly not reaching posterior margin of mesoscutum in dorsal view (Fig. 6D, G–H) ......................................................................................................................... 6

– Tegula with inner posterior margin straight or concave, more bean-shaped, and relatively large, reaching posterior margin of mesoscutum in dorsal view or nearly so (Fig. 6A–C, E–F) ............... 8

6. Punctures of face uniformly large and dense (Fig. 25A); mesoscutum punctures large, coarse and dense (i <1 pd) and very coarse, with many punctures touching laterad of parapsidal lines (i = 0 pd) except on anteromedian margin (i> 1.5 pd) (Fig. 26A); propodeum with oblique carina U-shaped and extending onto dorsolateral slope ........................ L. ameshoferi Landaverde-González sp. nov. – Punctures of upper half of face distinctly smaller and denser than punctures of lower half (Fig. 25B– C); mesoscutum punctures between parapsidal lines sparser (i = 1–3 pd) (Fig. 26B); propodeum with oblique carina straight, not extending onto dorsolateral slope ......................................................... 7

7. Mesepisternum slightly sparsely punctate (i ≤ 1–1.5 d) with dense plumose setae (1–1.5 OD); metapostnotum dull, imbricate, with shallow anastomosing rugae reaching posterior margin or nearly so; mesoscutal punctation between parapsidal lines sparse (i = 1.5–3 pd), becoming moderately dense but not crowded laterad of parapsidal lines (i = 1 pd; Fig. 27A); head about as long as broad (length/width 0.94–0.99) (Fig. 25B) .................................... L. milpa Landaverde-González sp. nov.

– Mesepisternum imbricate and densely punctate (i ≤ 1 pd); metapostnotum shiny to weakly tessellate, with strong, coarse rugae reaching posterior margin; mesoscutal punctation moderately sparsely punctate between parapsidal lines (i = 1–3 pd), becoming dense and crowded laterad of parapsidal lines (i ≤ 1 pd; Fig. 27B); head broader than long (length/width 0.91–0.95) (Fig. 25C) ................... ............................................................... L. nanotegula Landaverde-González & Husemann sp. nov.

8. T2 and usually T3 apical rims glabrous and impunctate (Fig. 28A); mesoscutum with sparse erect setae ~1 OD long (most setae separated by half their length or more in lateral view) and subappressed setae little more than stubble, appearing shaved (Fig. 29A); mesoscutum often with copper-red reflections medially ........................................................................................................................... 9

– T2–T3 apical rims evenly covered with fine setae and/or punctures (Fig. 28B); mesoscutum with dense erect setae ~1 OD long (all setae separated by less than half their length in lateral view) and subappressed setae 0.25–0.5 OD long (Fig. 29B); mesoscutum dark turquoise-green with golden reflections ........................................................................................................................................ 10

9. Tegula lateral margin with shallow, minute, and sparse punctures (i = 1–2 d) no larger than mesoscutum punctures (sometimes inconspicuous and tegula nearly impunctate) (Fig. 6B); mesonotum and mesepisternum shiny; mesepisternum granular with distinct fine and dense punctures (i = 1–1.5 pd) (Fig. 30A) .......................................................................... L. paxtoni Landaverde-González sp. nov.

– Tegula lateral margin with deep, distinct, and dense punctures (i <1 d) slightly larger than mesoscutum punctures (Fig. 6A); mesonotum and mesepisternum dull with strong microsculpture; mesepisternum strongly imbricate to finely rugulose and indistinctly punctate at least dorsal half (Fig. 30B) .................................................................. L. yucatanense Landaverde-González sp. nov.

10. Tegula deeply and distinctly punctate (similar to mesoscutum), usually densely (i <1 pd) (Fig. 6C); mesepisternum usually imbricate and moderately sparsely punctate (i = 1–2 pd) (Fig. 31A) ........... ............................................................................................................... L. stictaspis species complex

– Tegula finely punctate (punctures smaller than those of mesoscutum), usually sparsely (i ≥ 1.5 pd) (Fig. 6E–F); mesepisternum very densely punctate (i <0.5 pd) (Fig. 31B) ....................................11

11. Mesoscutum and supraclypeal area sparsely punctate (i = 1–3 pd); tegula with a few scattered minute punctures hardly visible at 40 × magnification (Fig. 6E); metapostnotum dull with shallow rugae blending into finely reticulate background microsculpture (Fig. 32A) .............................................. .............................................................. L. aureoviride Landaverde-González & Husemann sp. nov.

– Mesoscutum and supraclypeal area densely punctate (i = 0.5–1 pd); tegula distinctly punctate at 40 × magnification at least on lateral margins, where it is dense (i ≤ 1 pd; Fig. 6F); metapostnotum shiny with strong anastomosing rugae (Fig. 32B) ....................................... L. paralepidii Gardner sp. nov.

Key to known males of Lasioglossum (Dialictus) from the Yucatán Peninsula

1. Tegula ovoid and relatively small, clearly not reaching posterior margin of mesoscutum in dorsal view (as in Fig. 6D, G–H) ................................................................................................................ 2

– Tegula with inner posterior margin straight or concave, more bean-shaped, and relatively large, reaching posterior margin of scutum in dorsal view or nearly so (as in Fig. 6A–C, E–F) ............... 6

2. S3–S5 pubescence long (2–4 OD), erect, and densely plumose (Fig. 33A); propodeum dorsolateral slope smooth, with rugae not reaching posterior margin (Fig. 34A) ................................................ 3

– S3–S5 pubescence short (1–2 OD), suberect, and weakly plumose, appearing simple at <40 × magnification (Fig. 33B); propodeum dorsolateral slope sometimes roughened by rugae reaching posterior margin (Fig. 34B–C) .......................................................................................................... 4

3. S4–S5 with long setae limited to median portion, hidden in dorsal view; face broader than long .... ................................................................................................................... L. exiguum (Smith, 1879)

– S4–S5 with long setae on extreme lateral margins visible in dorsal view; face about as long as broad ............................................................................................................ L. deceptor (Ellis, 1914)

4. Metapostnotum with strong and coarse subparallel rugae extending onto and fully covering propodeum dorsolateral slope (Fig. 34C), usually with trace oblique carina present; retrorse lobe small; penis valve small and delicate .......................... L. ameshoferi Landaverde-González sp. nov.

– Metapostnotum with strong or somewhat finer rugae not extending onto propodeum dorsolateral slope except at base (Fig. 34B) and oblique carina absent ............................................................... 5

5. Mesepisternum densely punctate (i <1 pd) ........................................................................................ ............................................................... L. nanotegula Landaverde-González & Husemann sp. nov.

– Mesepisternum sparsely punctate (i = 1–3 pd) ........................ L. meteorum Gardner & Gibbs, 2020

6. Tegula with sparse punctures medially (i> 1.5 dp) (sometimes inconspicuous and tegula nearly impunctate) (Fig. 35A) ..................................................................................................................... 7

– Tegula with dense punctures medially (i ≤ 1dp) (Fig. 35B) ............................................................. 8

7. Mesoscutum with dense plumose setae 0.5–1.0 OD long (all setae separated by less than half their length in lateral view) (as in Fig. 29B); mesoscutum dark turquoise-green to olive green; retrorse lobe enlarged and wide; S8 median processs narrow and long; penis valve wide observed in lateral view ...................................................... L. aureoviride Landaverde-González & Husemann sp. nov.

– Mesoscutum with sparse plumose setae 0.5–1 OD long (most setae separated by half their length or more in lateral view, especially on posterior half) (as in Fig. 29A); mesoscutum golden-green to brassy; retrorse lobe small; S8 median process wide; penis valve small and delicate observed in lateral view ........................................................................ L. paxtoni Landaverde-González sp. nov.

8. Mesepisternum moderately sparsely punctate at least on ventral half (i = 1–2 pd) (as in Fig. 31A). ............................................................................................................... L. stictaspis species complex

– Mesepisternum densely punctate (i <1 pd) (as in Fig. 31B) ............................................................ 9

9. Mesoscutum with sparse plumose setae 0.5–1 OD long (most setae separated by half their length or more in lateral view, especially on posterior half) (as in Fig. 29A); metapostnotum somewhat shiny, finely and weakly reticulate, with strong subparallel rugae (Fig. 36A) .............................................. ................................................................................... L. yucatanense Landaverde-González sp. nov.

– Mesoscutum with dense plumose setae 0.5–1 OD long (all setae separated by less than half their length in lateral view) (as in Fig. 29B); metapostnotum shiny, with weak microsculpture and strong rugae (Fig. 36B) ................................................................................. L. paralepidii Gardner sp. nov.