Key to both sexes of the species of Triepeolus in South America

1. T1 without apical transverse band (only basal band or pair of anterolateral patches of pale tomentum present, which may on each side (or each) have short, medially directed posterolateral extension) (Figs 2B, 10B, 11B); if T1 extensively covered in pale tomentum, then tomentum on apical impressed area not forming distinct transverse band (Fig. 3B) .......................................................................... 2

– T1 with both basal and apical transverse bands (Figs 3A, 5B, 6B, 7B, 8, 12B, 14B, 16B) .............. 4

2. T1 with pair of anterolateral patches of yellow tomentum, each mesally convex, such that discal patch in dorsal view forming trapezoid or triangle with concave anterolateral sides (Fig. 10B). Paramedian band attaining or nearly attaining anterior margin of mesoscutum (Fig. 10B). Axilla with tip broadly rounded (Fig. 13A). Pseudopygidial area of female circular, with apical margin broadly convex (Fig. 10D)........................................................ T. flavipennis (Friese, 1916) (in part)

– T1 with basal band (or pair of anterolateral patches) of yellow tomentum, on each side (or each) mesally concave, such that discal patch in dorsal view semicircular (Figs 2B, 11B). Paramedian band (if present) not attaining anterior margin of mesoscutum (Fig. 2B). Axilla with tip distinctly pointed (Fig. 13B). Pseudopygidial area of female triangular, with apical margin concave (Figs 2D, 11D) ................................................................................................................................................... 3

3. Mesoscutum with well-defined paramedian band of yellow tomentum (Fig. 2B) .............................. .................................................................................................... T. alvarengai Moure, 1955 (in part)

– Mesoscutum with large anteromedial ovate patch of yellow tomentum (Fig. 3B), which may be sparser medially such that patch suggestive of ill-defined paramedian band (Fig. 11B) .................... ........................................................................................................... T. nemoralis (Holmberg, 1886)

4. T1 basal and apical transverse bands subparallel and joined on each side by distinct longitudinal band, such that discal patch in dorsal view transversely oblong (Figs 12B, 16B) ............................ 5

– T1 basal band arched and (except in T. rufotegularis) continuous with (and indistinguishable from) lateral longitudinal band, such that discal patch in dorsal view reniform, semicircular, trapezoidal, or triangular (Figs 3A, 5B, 6B, 7B, 8, 14B) ...................................................................................... 6

5. Pro- and mesotrochanters not tuberculate (Fig. 15A). Axilla and mesoscutellum reddish brown and sparsely punctate (most i ≥ 1d) (Figs 12A–C, 13C). Pseudopygidial area of female circular, with apical margin broadly convex (Fig. 12D)......................................... T. osiriformis (Schrottky, 1910)

– Pro- and mesotrochanters distinctly tuberculate (Fig. 15B). Axilla and mesoscutellum black and densely punctate (most i <1d) (Figs 13D, 16A–C). Pseudopygidial area of female triangular, with apical margin concave (Fig. 16D)...... T. tuberculifer Onuferko, Rightmyer & Roig-Alsina sp. nov.

6. Dorsum of mesosoma (at least anterolaterally) with dense, long (≥ ½ MOD), erect/suberect, minutely branched setae (Fig. 4A–B) ............................................................................................................... 7

– Dorsum of mesosoma with only short (<½ MOD), appressed, branched setae (Fig. 4C–D)........... 8

7. Mesopleuron with dense, long (≥ ½ MOD), erect/suberect, minutely branched setae only in upper half, with sparse, erect, simple setae among short (<¼ MOD), appressed, branched setae in ventrolateral half (Fig. 4A). T1–T4 transverse bands all widely interrupted medially in both sexes (Fig. 5B)................................................................................................. T. atoconganus Moure, 1955

– Mesopleuron with dense, long (clearly>½ MOD), erect/suberect, minutely branched setae throughout (Fig. 4B). At least T3–T4 with apical transverse bands narrowed or narrowly interrupted medially (Figs 7B, 8) ..................................................................................... T. cecilyae Packer, 2016

8. T2–T4 apical transverse bands complete (Fig. 3A)........................................................................... 9

– T2–T4 apical transverse bands all interrupted medially (Figs 6B, 14B)......................................... 10

9. T1 basal band mesally concave, such that discal patch in dorsal view semicircular (Fig. 3A). Paramedian band not attaining anterior margin of mesoscutum (Fig. 3A). Axilla with tip distinctly pointed (Fig. 3A). Pseudopygidial area of female triangular, with apical margin concave (Fig. 2D) ..................................................................................... T. alvarengai Moure, 1955 (in part)

– T1 basal band on each side mesally convex, such that discal patch in dorsal view forming trapezoid or triangle with concave anterolateral sides (Fig. 10B). Paramedian band attaining or nearly attaining anterior margin of mesoscutum (Fig. 10B). Axilla with tip broadly rounded (Fig. 13A). Pseudopygidial area of female circular, with apical margin broadly convex (Fig. 10D) .................... .................................................................................................. T. flavipennis (Friese, 1916) (in part)

10. T2 apical transverse band with pair of lobe-like anterolateral extensions (Fig. 6A–C). Metasomal terga with bands of pale-yellow tomentum (Fig. 6) [Ecuador and Peru] ............................................ ................................................................................................................. T. buchwaldi (Friese, 1908)

– T2 apical transverse band without lobe-like anterolateral extensions (Fig. 14A–C). Metasomal terga with bands of white to off-white tomentum (Fig. 14) [Caribbean region] .......................................... ....................................................................................................... T. rufotegularis (Ashmead, 1900)