Key for major males
1	Basal part of ventrite I, between metacoxae modified (elevated or elevated and with small punctures) (Figs 8E, 9H, 18E, 21I–J, 22E)	2
–	Basal part of ventrite I, between metacoxae not modified (Figs 5E, 10E, 13E, 14E, 16E)	6
2	Basal part of ventrite I, between the metacoxae elevated and with small punctures (Fig. 21I–J)	Deltochilum ventripuncturatus sp. nov.
–	Basal part of ventrite I, between the metacoxae elevated, without small punctures (Figs 8E, 9H, 18E, 22E)	3
3	Mesofemur with basal denticle on the posterior edge (Fig. 9G)	Deltochilum tyba sp. nov.
–	Mesofemur without a basal denticle, at most with a basal sinuation (Figs 19A, 23A)	4
4	Punctures on anterior part of head larger than head discal punctures (Fig. 22A)	Deltochilum nobile sp. nov.
–	Punctures on anterior part of head slightly larger than head discal punctures (Figs 18A, 24A, 25A)	5
5	Tubercles at elytral apex on interstriae II–VII (Fig. 19C)	Deltochilum altiventris sp. nov.
–	Tubercles at elytral apex on interstriae III, V–VII (Figs 24E, 25C)	Deltochilum plebejum Balthasar, 1939
6	Mesofemur with basal denticle on posterior edge (Fig. 6G)	Deltochilum abdominale Martínez, 1947
–	Mesofemur without a basal denticle, at most with a basal sinuation (Figs 11A, 13A, 15A, 17A)	7
7	Medial-lateral angle of pronotum salient (Fig. 17G). Punctures on anterolateral areas of the metaventral process not fully closed and occupying a significant portion of these areas (Figs 3E, 16D)	Deltochilum pauxi sp. nov.
–	Medial-lateral angle of pronotum rounded (Figs 10B, 12B, 14B). Punctures on anterolateral areas of the metaventral process fully closed and occupying a small portion of these areas (Figs 3D, 10D, 12D, 14D)	8
8	Width of the expansion of ventrite I (on ventrite III), almost as wide as the distance between mesocoxae (Fig. 13E)	Deltochilum parapseudoabdominale sp. nov.
–	Width of the expansion of ventrite I (on ventrite III), narrower than the distance between mesocoxae (Figs 10E, 14E)	9
9	Width of the expansion of ventrite I (on ventrite III), narrower than the distance between mesocoxae (Fig. 10E). Tubercles at elytral apex on the interstriae III, V–VII (Fig. 11C)	Deltochilum pseudoabdominale sp. nov.
–	Width of the expansion of ventrite I (on ventrite III), much narrower than the distance between mesocoxae (Fig. 14E). Tubercles at elytral apex on the interstriae III–VII (Fig. 15C)	Deltochilum picachos sp. nov.
Key for minor or medium-sized males
1	Basal part of ventrite I, between the metacoxae modified (elevated or elevated and with small punctures) (Figs 8E, 9H, 18E, 21I–J, 22E, 25B–C)	2
–	Basal part of ventrite I, between the metacoxae not modified (Figs 5E, 10E, 13E, 14E, 16E)	6
2	Basal part of ventrite I, between the metacoxae elevated and with small punctures (Fig. 21I–J)	Deltochilum ventripuncturatus sp. nov.
–	Basal part of ventrite I, between the metacoxae elevated, but without small punctures (Figs 8E, 9H, 18E, 22E, 25B–C)	3
3	Punctures on anterior part of head larger than head discal punctures (Fig. 22A)	Deltochilum nobile sp. nov.
–	Punctures on anterior part of head with almost the same size or slightly larger than head discal punctures (Figs 8A, 18A, 24A, 25A)	4
4	Internal carina of metatibia, forming small tubercles (Fig. 9B)	Deltochilum tyba sp. nov.
–	Internal carina of metatibia elevated or slightly elevated, that elevation normally reduced on the middle of the metatibial length, giving the appearance of two carinae (Figs 19B, 25A–B)	5
5	Tubercles at elytral apex on interstriae II–VII (Fig. 19C)	Deltochilum altiventris sp. nov.
–	Tubercles at elytral apex on interstriae III, V–VII (Figs 24E, 25C)	Deltochilum plebejum Balthasar, 1939
6	Mesofemur with basal denticle on posterior edge (Fig. 6A). Striae almost inconspicuous, width of third stria on disc ~1/55 of the distance between striae II and III (Fig. 5C)	Deltochilum abdominale Martínez, 1947
–	Mesofemur without a basal denticle, at most with a basal sinuation (Figs 11A, 13A, 15A, 17A). Striae conspicuous, width of third stria on disc ~1/20–1/30 of the distance between striae II and III (Figs 10C, 12C, 14C, 16C)	7
7	Medial-lateral angle of pronotum salient (Fig. 16B). Punctures on anterolateral areas of metaventral process not fully closed and occupying a significant portion of these areas (Figs 3E, 16D)	Deltochilum pauxi sp. nov.
–	Medial-lateral angle of pronotum rounded (Figs 10B, 12B, 14B). Punctures on anterolateral areas of metaventral process fully closed and occupying a small portion of these areas (Figs 3D, 10D, 12D, 14D)	8
8	Width of the expansion of ventrite I (on ventrite III), almost as wide as the distance between mesocoxae (Fig. 13E)	Deltochilum parapseudoabdominale sp. nov.
–	Width of the expansion of ventrite I (on ventrite III), narrower than the distance between mesocoxae (Figs 10E, 14E)	9
9	Width of the expansion of ventrite I (on ventrite III), narrower than the distance between mesocoxae (Fig. 10E). Tubercles at elytral apex on interstriae III, V–VII (Fig. 11C)	Deltochilum pseudoabdominale sp. nov.
–	Width of the expansion of ventrite I (on ventrite III), much narrower than the distance between mesocoxae (Fig. 14E). Tubercles at elytral apex on interstriae III–VII (Fig. 15C)	Deltochilum picachos sp. nov.
Key for females (also applicable to males)
1	Interstrial shiny points subequal in size to interstrial punctures (Fig. 5C)	Deltochilum abdominale Martínez, 1947
–	Interstrial shiny points smaller than interstrial punctures (Figs 8C, 10C, 12C, 14C, 16C, 18C, 20C, 22C, 24C)	2
2	Punctures on anterolateral areas of metaventral process not fully closed (Figs 3E, 16D, 18D, 25B)	3
–	Punctures on anterolateral areas of metaventral process fully closed (Figs 3D, 8D, 10D, 12D, 14D, 20D, 22D)	5
3	Medial-lateral angle of pronotum salient (Figs 16B, 17G). Interstrial punctures separated by one diameter of each puncture (Fig. 16C)	Deltochilum pauxi sp. nov.
–	Medial-lateral angle of pronotum rounded (Figs 18B, 24B, 25A). Interstrial punctures separated by approximately two diameters of each puncture (Figs 18C, 24C)	4
4	Tubercles at elytral apex on interstriae II–VII (Fig. 19C)	Deltochilum altiventris sp. nov.
–	Tubercles at elytral apex on interstriae III, V–VII (Figs 24E, 25C)	Deltochilum plebejum Balthasar, 1939
5	Striae thin, in some species almost inconspicuous (Figs 8C, 20C, 22C)	6
–	Striae wide, striae always conspicuous (Figs 10C, 12C, 14C)	8
6	Punctures on anterior part of head smaller than head discal punctures (Fig. 20A)	Deltochilum ventripuncturatus sp. nov.
–	Punctures on anterior part of the head from almost same size to larger than head discal punctures (Figs 8A, 22A)	7
7	Punctures on the anterior part of head larger than head discal punctures (Fig. 22A)	Deltochilum nobile sp. nov.
–	Punctures on anterior part of head slightly larger than head discal punctures (Fig. 8A)	Deltochilum tyba sp. nov.
8	Tubercles at elytral apex on interstriae III–VII (Fig. 15C)	Deltochilum picachos sp. nov.
–	Tubercles at elytral apex on interstriae III, V–VII (Figs 11C, 13C)	9
9	Punctures on anterolateral areas of metaventral process separated by less than one diameter of each puncture (Fig. 10D). Punctures on anterior part of head with almost the same size than head discal punctures (Fig. 10A)	Deltochilum pseudoabdominale sp. nov.
–	Punctures on anterolateral areas of metaventral process separated by one diameter of each puncture (Fig. 12D). Punctures on anterior part of head slightly larger than head discal punctures (Fig. 12A)	Deltochilum parapseudoabdominale sp. nov.