Genus Psephenops Grouvelle, 1898 This genus is recognized by a pronotum expanded laterally on posterior half, with a well-developed carina; maxillary palp is short with last palpomere the longest; first and second tarsomeres, and occasionally the third, with wide ventral expansion that covers apical tarsomere (Arce-Pérez et al. 2012). Key to adult males of New World species of Psephenops Grouvelle (Based on Arce-Pérez & Novelo-Gutiérrez 2017 and Barr & Shepard 2024; the species P. robacki (Spangler, 1966), was not included in the key because only description of the female is available). 1. Pronotum with 3 small tuberculiform prominences; elytra with several longitudinal ridges on disc.............. grouvellei - Pronotum without tuberculiform prominences; elytra without longitudinal ridges on disc............................. 2 2. Protibiae without apicolateral denticle; male genitalia as in figure 26...................................... prestone - Protibiae with apicolateral denticle; male genitalia variously arranged............................................ 3 3. Tarsal lobes enlarged (lobe of tarsomere 2 covers ventrally the full-length of tarsomeres 3-4 and reaching at least 80% the length of tarsomere 5)....................................................................................... 4 - Tarsal lobes short (reaching the basal half or less of tarsomere 5)................................................ 5 4. Basal half of parameres, in dorsal view, separated by a deep cleft (Fig. 32)........................................ 7 - Basal half of parameres, in dorsal view, fused (Fig. 37)....................................................... 9 5. Parameres apically truncated (Fig. 27); 4th maxillary palpomere at least twice as long as preceding palpomeres together smithi - Parameres not apically truncated; 4th maxillary palpomere not as above.......................................... 6 6. Parameres strongly convergent on apical third, medial margins of parameres separated from each other by a narrow, drop-like cleft (Fig. 28).................................................................................... lupita - Parameres more or less parallel on apical third, medial margins of parameres separated from each other by a wide, U-shaped cleft (Fig. 29).................................................................................. shepardi 7. Apex of parameres, in dorsal view, spine-like, widely divergent (Fig. 30)............................... spiniparameri - Apex of parameres, in dorsal view, not spine-like, convergent (Figs. 28, 29)....................................... 8 8. Prosternal process flat, with apex lanceolate. Penis with a small, lateral tooth (Fig. 31)....................... mexicanus - Prosternal process subcylindrical, with apex bifid. Penis lacking lateral projections (Fig. 32)...................... bifidus 9. Small individuals, length less than 2.4 mm; antennae moniliform-serrate; parameres truncate, with apex straight (Fig. 33)............................................................................................. panamaensis - Large individuals, length greater than 2.5 mm; antennae not serrate; parameres not truncate......................... 10 10. Antennae long, filiform; fore- and middle legs with segments 1 and 2 lobulate, hind legs only with segment 1 lobulate (Haiti)............................................................................................. haitianus - Antennae short, moniliform; all legs with segments 1 and 2 lobulate............................................ 11 11. Elytra slightly striate.................................................................................. 12 - Elytra smooth....................................................................................... 14 12. Parameres in dorsal view widened on apical fifth, with apex rounded; penis slightly produced apically (Fig. 34). maculicollis - Parameres in dorsal view uniformly broad; penis not produced apically......................................... 13 13. Parameres in dorsal view short, with apices broadly but unevenly rounded; penis with apex semi-truncate (Fig. 35)...... trini - Parameres in dorsal view elongate, apices evenly rounded; penis with apex rounded (Fig. 36)............... argentinensis 14. Parameres in dorsal view broadly separate, apex subtriangular; penis digitiform, with a basal, lateral, subtriangular projection from each side (Fig. 37)........................................................................ triangularis - Parameres in dorsal view close to each other, apex rounded (Fig. 38); penis acuminate apically (Figs. 13, 14).. arcei, sp. nov.

Published as part of Chacón-Hartleven, Erick A., Luna-Luna, Alba Magali, Chamé-Vázquez, Eduardo R., Mejía-González, Gamaliel & Contreras-Ramos, Atilano, 2025, A new species of Psephenops Grouvelle, 1898, with new distribution data and habitat notes of the psephenine water-penny beetles from Mexico (Coleoptera: Psephenidae: Psepheninae), pp. 79-94 in Zootaxa 5722 (1) on pages 83-92, DOI: 10.11646/zootaxa.5722.1.3, http://zenodo.org/record/17891804