Psephenops trini Barr and Shepard, 2024

Barr, Cheryl B. & Shepard, William D., 2024, A taxonomic review of the genus Psephenops Grouvelle of the Lesser Antilles with description of new species Psephenops trini, and reassignment of Peruvian species Psephenus robacki Spangler (Coleoptera: Psephenidae: Psepheninae), Insecta Mundi 2024 (45), pp. 1-22 : 11-17

Psephenops trini Barr and Shepard , new species urn:lsid:zoobank.org:pub:B226E04A-5E95-4576-8BDB-6F35647B6D81

( Fig. 9–12 )

Type locality. Trinidad and Tobago: Trinidad, St. George County, Arima River at Verdant Vale ; 10.6930°, −61.2928°; elevation 180 m ( Fig. 13 ).

Diagnosis. Of the described species of Psephenops , only Psephenops trini is geographically close to P. smithi from Grenada and St. Vincent. Males of these two species can be separated by characteristics of the maxilla: In P.trini ( Fig. 9b ), the terminal maxillary palpomere is slightly wider than, and about as long as, palpomeres 2 + 3; in P. smithi ( Fig. 3a , 5c ) the terminal maxillary palpomere is much stouter, about 3× wider than, and nearly 2× longer than, palpomeres 1–3. The body shape and proportions of the females differ considerably between the two species: Females of P.trini ( Fig. 11 ) are proportionally wider (approximate L/W about 1.8:1); P. smithi (= X. latus ) females ( Fig. 7, 8 ) are more elongate (approximate L/W about 2.2:1). Also, in P. trini females the pronotal anterior angles are broadly rounded and the posterior angles are semi-truncate; in P. smithi the anterior angles are narrower, and the posterior angles are broadly rounded. Since these observations are based on a small number of P. smithi specimens (n = 6; 4♂, 2♀), they do not reflect much variability and are likely somewhat incomplete.

In the key to Mesoamerican Psephenops species by Arce-Perez and Novelo (2017), P.trini keys to the last couplet (#11) where it fits neither P. maculicollis nor P. triangularis . The aedeagus of P.trini ( Fig. 10 ) bears some resemblance to the aedeagus of P. smithi in Delève (1967) and the illustration by Sohn ( Fig. 6 ).

Description ( Fig. 9–10 ). Holotype male. Body 2.43 mm long, 1.20 mm wide; head, pronotum, scutellum black; antennae, elytra, legs brown; venter brown, pruinose. Head with moderately long, erect setae; long curved setae arching over eyes; frons slightly depressed between eyes; interantennal area as wide as eye. Clypeus transverse, wider than long; deflected at 90° to frons; apex widely emarginate; disc densely setose. Labrum transverse, emarginate, disc setose. Maxillary palpus with 4 palpomeres; palpomere 1 very short; palpomere 2 elongate, slightly longer than 3; palpomere 4 wider, 3× as long as wide, as long as 2 + 3, slightly flattened, apex rounded. Labial palpus very short, with 3 palpomeres; palpomere 3 shortest, digitiform. Antenna moderately short, shorter than pronotum; moniliform with 11 setose antennomeres; antennomeres 1 and 2 curved to fit under eye; antennomere 1 longest, about 2× as long as wide; antennomere 2 globular, as wide as antennomere 1 but 1/2 as long; antennomere 3 triangular, narrow at base, wider apically; antennomeres 4–11 moniliform; antennomere 11 bluntly rounded at tip. Eyes large, hemispherical, finely faceted. Pronotum trapezoidal, 0.55 mm long, 0.98 mm wide; covered with velutinous setae and long erect dark setae. Anterior margin weakly arcuate; lateral sides strongly diverging posteriorly; posterior margin bisinuate, straight in antescutellar area; anterior angles almost indistinguishable; posterior angles narrowly rounded, explanate, reflexed. Disc convex in anterior 1/2, depressed posteriorly, deepest adjacent to midline; median longitudinal carina in basal 1/2 prominent, glabrous, ending short of basal margin. Scutellar shield flat, equilaterally triangular, covered with velutinous setae. Elytron shorter than abdomen, 1.6 mm long, 0.60 mm wide, widest at posterior 1/3; consistency flexible, leathery; setose with short, fine, recumbent setae and longer, erect setae. Disc flat, weakly striate, impunctate, intervals slightly raised; apex broadly rounded, dehiscent. Prosternum much shorter than wide; very setose; slightly depressed except where carinate posteromedially at margin with hypomeron. Prosternal process elongate, extending to middle of mesocoxae, slightly narrowed between procoxae, apex narrowly rounded. Mesoventrite very short, wide. Metaventrite convex; covered with moderately long, semi-erect setae and short, dense setae; metathoracic discrimen extending from near anterior margin to round pit at posterior margin; metanepisternum inner margin carinate; metepimeron a concave lobe at posterolateral metanepisternal margin. Legs similar, heavily setose. Pro- and mesocoxa globose, each with a transverse lateral extension; metacoxa very short, transverse, laterally narrow; trochanter triangular. Femur widest before middle, metafemur widest. Tibia longer than femur, straight, slightly enlarged at apex. Tarsus with 5 tarsomeres; tarsomeres 1 and 2 modified with long, densely setose, ventral laminar expansions underlying the tarsomeres; ventral expansion of tarsomere 1 cylindrical to ovoid; ventral expansion of tarsomere 2 narrow at base, flared apically, concave and partly enclosing tarsomeres 2–5; tarsomeres 3 + 4 shorter than tarsomere 5; tarsomere 5 extending beyond laminar expansion of tarsomere 2; tarsal claws fine, simple. Abdomen densely setose; with 7 ventrites, all transverse except ventrite 7, all subequal in length except for ventrite 6; ventrite 1 barely extending beyond metatrochanters; ventrite 6 very short; ventrite 7 small, rectangular, convex [Note: ventrites 6 and 7 were removed during dissection of the aedeagus and are stored in the genitalia vial]. Aedeagus ( Fig. 10 ) nearly twice as long as wide. Phallobase slightly longer than parameres, weakly sclerotized. Parameres broad, open ventrally, fused dorsally except for a median, Y-shaped notch; basal 2/3 sclerotized, apical 1/3 membranous, translucent; apices broadly but unevenly rounded. Penis extending beyond parameres; broad, at base nearly as wide as phallobase, apical 1/3 narrowed; membranous laterally, well-sclerotized medially except at apical 1/6; with ventral, sclerotized, longitudinal sclerite widely bifid basally and apically; apex semi-truncate.

Female description ( Fig. 11 ). Body 3.38–3.85 mm long, 1.63–2.00 m wide (n = 7); color similar to male. Pronotum trapezoidal, wider than long, 0.70–0.83 mm long, 1.35–1.63 mm wide, widest at base; laterally explanate; posterior angles concave, produced, explanate, laterally semi-truncate. Elytron shorter than abdomen, 2.15–2.63 mm long, 0.81–1.00 mm wide, widest at apical 1/3; apex broadly rounded, dehiscent. Prosternal process broad, sword-shaped, with median longitudinal carina; apex narrowly rounded. Tarsus slender, unmodified, lacking ventral laminar expansions; tarsomeres 1–4 together as long as tarsomere 5. Abdomen with 6 ventrites. Ovipositor short, broad, lightly sclerotized; paraproct 2/3 length of ovipositor, lateral margin generally parallel-sided, medial margin sinuate; each proximal gonocoxite transverse, short, 1/3 length of distal gonocoxite, slanting medially to join other proximal gonocoxite at midline; short V-shaped sclerite between coxite bases on dorsum; distal gonocoxite largely unsclerotized; gonostyli very short, as long as wide; ovipositor poorly sclerotized ventrally.

Variation. Females ( Fig. 11 ) are larger than males ( Fig. 9 ). There is a slight overlap in length, but females are much broader: females 3.38–3.85 mm long, 1.63–2.00 m wide (n = 7); males 2.43–3.53 mm long, 1.20–1.40 mm wide (n = 6). The sexes are sexually dimorphic; besides size, they differ in pronotal shape, tarsal form, and the number of abdominal ventrites, as noted above in the female description.

Type material. Holotype male, pinned, deposited in EMEC, labeled: “TRINIDAD: St. George / Co., Verdant Vale / 9 VII 2005 / Arima River 590 ft [180 m] / 10°41.58′N 61°17.57′W / WDS-A-1654 [on reverse] // William D. / Shepard, leg. // HOLOTYPE / Psephenops trini / Barr & Shepard [red label, handwritten] // UC Berkeley / EMEC / 49614 ” . Paratypes (n = 29; 22♂, 7♀). Trinidad. TRINIDAD: 6.8 km S /of Blanchisseuse / 6 VII 2005 80 ft [24 m] / Marianne River / 10°46′N 61°18′W / WDS-A-1649 [on reverse] // William D. / Shepard, leg. (1♂ EMEC) ; TRINIDAD: St. George Co. / Marianne River 6.8 km / S of Blanchisseuse / 6-VII-2005, C. B. Barr // 10°45.9′N, 61°18.2′W / elevation 80 ft. [24 m] (1♀ EMEC) ; TRINIDAD: just E of / Blanchisseuse / 7 VII 2005 / Marianne River / WDS-A-1650 [on reverse] // William D. / Shepard, leg. (1♀ EMEC) ; TRINIDAD: 6.8 km S / Blanchisseuse / 8 VII 2005 80 ft [24 m] / Marianne River / 10°46′N 61°18′W / WDS-A-1652 [on reverse] // William D. / Shepard, leg. (1♂, 1♀ EMEC; 1♀ NHMUK; 1♀ USNM; 1♀ UWIZM) ; TRINIDAD: St. George / Co. , Naranjo River / along Waterfall Rd. / 1 km NE Maracas / 10-VII-2005, C.B. Barr // 10°43.05′ N / 61°24.42′ W / elev. 350 ft. [107 m] (1♂ EMEC) ; TRINIDAD: 1.5 km E / of Valencia / 11 VII 2005 120 ft [37 m] / Caroni [Quare] River 10°39′N 61°15′W / WDS-A-1658 [on reverse] // William D. / Shepard, leg. (4♂, 1♀ EMEC; 1♂ NHMUK; 1♂ USNM; 3♂ UWIZM) ; TRINIDAD: St. Andrew / County , Quare [Caroni] River / at Valencia Road / 1.5 km E of Valencia / 11-VII-2005 ,

C.B. Barr // 10°39.15′ N / 61°11.44′ W / elevation 120 ft. [37 m] (5♂ EMEC). Tobago. TOBAGO: 2.1 km NW / of Whim / 15 VII 2005 36 m / Courland River / 11°13′N 60°44′W / WDS-A-1662 [on reverse] // William D. / Shepard, leg. (1♂ EMEC) ; TOBAGO: Courland / River at Providence / Rd. 2 km NW Whim / 15-VII-2005, C.B. Barr // 11°12′54.7″N / 60°44′36.1″W (3♂ EMEC) ; TOBAGO: 1 km E of / Parlatuvier / 16 Vii 2005 / 11°17′N 60°39′W / WDS-A-1664 [on reverse] // William D. / Shepard, leg. (1♂ EMEC) .

Other material examined (n = 3♂). Trinidad. TRINIDAD: St.Andrew / Co., Rio Seco at Toco / Main Rd. just E Salybia / 12-VII-2005, C.B. Barr // 10°42.4′ N / 61°01.4′ W / elevation 10 ft. [3 m] (1♂ EMEC, pinned, all legs missing,); TRINIDAD: 5.8 km W / of Blanchisseuse / 7 VII 2005 10 ft [3 m] / Yarra River / 10°48′N 61°21′W / WDS-A-1651 [on reverse] // William D. / Shepard, leg. (1♂ EMEC, in ethanol, damaged). Tobago. UCONHM 7424 / Arthropoda / Insecta / Coleoptera / Psephenidae / Psephenops / smithi / Delaford Cr. [Louis d’Or Nurseries], / Delaford, Tobago / 5/31/1996 / D. Bass (1♂ UCOCI, in ethanol).

Larval description ( Fig. 12 ). Late instar. Body 5.0–6.0 mm long; oval, wider anteriorly; dorsally convex; dorsal color greenish-yellow laterally, yellow medially with brown mottling and pale anastomosing lines of brown cuticular beads; outer 1/2 of the body transparent; entire lateral margin fringed with hair-like, basally sclerotized setae; venter white to pale yellow except paratergites darker laterally. Dorsally, thoracic tergites form the anterior half of body; abdominal tergites I–IX form the posterior half of body. Pronotum to AB VII with paratergites; paratergites of AB VII clasping AB VIII and AB IX laterally; lateral margins of paratergites AB VII and AB IX forming a continuous margin. Pronotum to AB VII with tergopleural sutures; median longitudinal suture from pronotum to AB VII; pro- to metathorax with pairs of oblique sulci extending medially from tergopleural sutures; meso- and metathorax with pairs costal lines; AB I with a pair of short, oblique sulci extending from base to tergopleural sutures. Abdominal tergite VIII rectangular, 2.5× wider than long, apicolateral angles with a pair of spiracular tubercles; AB IX subrectangular, 1.6× wider than long, apical margin broadly arcuate.

Ventrally with head completely covered by pronotum; ecdysal line V-shaped, extending from base of head to antennal bases; frons with long seta at base of antenna. Antenna relatively long (sensu Lee et al. 2007: 9), reaching much of the way to body margin, with 3 antennomeres; antennomeres 1 and 2 elongate, slender, cylindrical, antennomere 3 peg-like; antennomere 1 longest with two thick subapical setae, antennomere 2 about 2/3 as long as 1 (5× longer than wide) with one very short apical seta, antennomere 3 minute, as long as width of antennomere 2 and as long as its apical seta. Eyespot consisting of a roughly circular cluster of stemmata. Clypeus apically deeply emarginate; labrum and labium covering mandibles; labrum apically truncate with marginal brush of short setae; maxillary palpus short, with 4 palpomeres, terminal palpomere very short; labial palpus short, with 3 palpomeres. Legs each with coxa long, about as long as trochanter + femur; femur narrowest basally, widest apically; tarsungulus shorter than femur, with one short, stout, blunt-tipped claw. Gills ventral, pectinate, 5 pairs on AB II–AB VI. AB IX with basal, oval operculum covering anus 1/3 width of ventrite.

Larval material examined. Trinidad. TRINIDAD: Asa / Wright Nat Ctr / 6 VII 2005 1210 ft [369 m] / Unnamed stream / 10°47′N 61°18′W / WDS-A-1648 [on reverse] // William D. / Shepard, leg. (1 EMEC) ; TRINIDAD: 6.8 km S / Blanchisseuse / 6 VII 2005 80 ft [24 m] / Marianne River / 10°46′N 61°18′W / WDS-A-1649 [on reverse] // William D. / Shepard, leg. (16 EMEC) ; TRINIDAD: St. George Co. / Marianne River 6.8 km / S of Blanchisseuse / 6-VII-2005, C. B. Barr // 10°45.9′N, 61°18.2′W / elevation 80 ft. [24 m] (3 EMEC) ; TRINIDAD: 6.8 km S / Blanchisseuse / 8 VII 2005 80 ft [24 m] / Marianne River / 10°46′N 61°18′W / WDS-A-1652 [on reverse] // William D. / Shepard, leg. (65 EMEC, 10 UWIZM) ; TRINIDAD: Blanchisseuse / 7 VII 2005 / WDS-A-1650 [on reverse] // William D. / Shepard (31 EMEC) ; TRINIDAD: 5.8 km W / of Blanchisseuse / 7 VII 2005 10 ft [3 m] / Yarra River / 10°48′N 61°21′W / WDS-A-1651 [on reverse] // William D. / Shepard, leg. (3 EMEC) ; TRINIDAD: St.George / Co., Yarra River at / No. Coast Rd. 5.8km / W of Blanchisseuse / 7-VII-2005, C.B. Barr // 10°47.6′N, 61°20.8′W / elevation 10 ft. [3 m] (5 EMEC) ; TRINIDAD: 1 km uphill / Asa Wright Nat Ctr / 9 VII 2005 1360 ft [415 m] / upper Arima River / WDS-A-1653 [on reverse] // William D. / Shepard, leg. (2 EMEC) ; TRINIDAD: St. George / Co., Verdant Vale / 9 VII 2005 / Arima River 590 ft [180 m] / 10°41.58′N 61°17.57′W / WDS-A-1654 [on reverse] // William D. / Shepard, leg. (67 EMEC) ; TRINIDAD: St.George / Co., Arima River / at Verdant Vale / 9-VII-2005, C.B. Barr (1 EMEC) ; TRINIDAD: Asa Wright / Nature Center / 9 VII 2005 / upper Arima River / 10°43′N 61°18′W / WDS-A-1655 [on reverse] // William D. / Shepard, leg. (1 EMEC) ; TRINIDAD: 1 km NE / of Maracas / 10 VII 2005 350 ft [107 m] / upper Maracas River / 10°43′N 61°25′W / WDS-A-1656 [on reverse] // William D. / Shepard, leg. (15 EMEC) ; TRINIDAD: St. George / Co., Naranjo River / Waterfall Rd. NE Maracas / 10-VII-2005, C.B. Barr // 10°43.05′ N / 61°24.42′ W / elev. 350 ft. [107 m] (1 EMEC) ; TRINIDAD: 1.5 km E / of Valencia / 11 VII 2005 120 ft [37 m] / Caroni [Quare] River / 10°39′N 61°15′W / WDS-A-1658 [on reverse] // William D. / Shepard (5 EMEC) ; TRINIDAD: 8.4 km E / of Valencia / 11 VII 2005 100 ft [35 m] / Oropuche River / 10°40′N 61°08′W / WDS-A-1659 [on reverse] // William D. / Shepard, leg. (1 EMEC) . Tobago. TOBAGO: 2.5 km E / of Castara / 16 VII 2005 / unnamed stream / 11°17′N 60°41′W / WDS-A-1663 [on reverse] // William D. / Shepard (3 EMEC) ; TOBAGO: unnamed / stream at Northside Rd. / 2.5 km NE Castara / 16-VII-2005, C. B. Barr // 11°17′17.2″ N / 60°40′52.4″ W (1 EMEC) .

Etymology. The trivial name, trini , is a Caribbean informal term for Trinidadians, the current inhabitants of Trinidad. It is a gender-neutral noun in apposition.

Distribution. Trinidad, Tobago, Trinidad and Tobago (country), West Indies ( Fig. 1 ).

Habitat. Psephenops trini occurs in shallow streams and rivers with substrates composed of rocks, cobbles, gravel, and sand ( Fig. 13–16 ). Larvae are found submerged on rocks, and adults are found on submerged or emergent parts of rocks and on vegetation closely overhanging streams. Larvae and/or adults have been collected at elevations of 3–415 m, the lower of which are close to the coast.

Associated aquatic Dryopoidea. The following taxa were collected in some of the same streams as P.trini : Elmidae : Heterelmis simplex Sharp , Hexacylloepus smithi (Grouvelle) , Macrelmis clypeata (Hinton) , Microcylloepus carinatus Hinton , Neoelmis pusio Hinton , Phanocerus congener Grouvelle ; Dryopidae : Dryops sp.

All of the above elmids were previously reported by Hinton (1971) from Trinidad and Tobago, and by Bass (2003) from Tobago. Hinton did not mention whether or not he also collected psephenids and dryopids during his fieldwork. The OMNH has one specimen from Trinidad identified as Dryops aequinoxialis Grouvelle ( Dryopidae ) in their Recent Invertebrates database.

Remarks. We found no other psephenids but P.trini on the islands of Trinidad and Tobago. During our sampling we collected adults at nine of the 30 streams sampled, and larvae at 12 of 30. Although Bass (2003) cited P. smithi from Tobago, we examined his adult male specimen and determined it to be P.trini rather than P. smithi . Records of P. smithi from Trinidad and Tobago that appear on the GBIF website also most likely represent P. trini .

Figures

Figure 1. Map of the southern West Indies: the Lesser Antilles, Barbados, Tobago, and Trinidad.

Figure 5. Psephenops smithi Grouvelle, adult male from St. Vincent. a) Dorsal habitus. b) Ventral habitus. c) Lateral habitus. d) Specimen labels. Photographs courtesy of Karolyn Darrow, USNM.

Figure 6. Psephenops smithi Grouvelle, aedeagus. a) Dorsal view. b) Lateral view. Illustrations by Y. Sohn †, courtesy of the USNM.

Figures 9–10. Psephenops trini new species, adult male. 9) Habitus, 2.85 mm long. a) Dorsal. b) Ventral. 10) Aedeagus. a) Dorsal view with attached abdominal ventrites. b) Lateral view. c) Ventral view.

Figures 11–12. Psephenops trini new species, adult female and larva. 11) Adult female habitus, 3.85 mm long.a) Dorsal view. b) Ventral view. 12) Larva. a) Dorsal habitus. b) Ventral habitus.

Figures 13–16. Psephenops trini new species, stream collection sites in Trinidad. 13) Arima River at Verdant Vale, type locality. 14) Quare/Caroni River near Valencia. 15) Marianne River south of Blanchisseuse. 16) Lower Marianne River east of Blanchisseuse.

Figures 2–4. Psephenops smithi Grouvelle, adult males. 2) Lectotype from St. Vincent. a) Dorsal habitus. b) Specimen labels. 3) Paralectotype from St. Vincent. a) Ventral habitus with dissected maxillary and labial palpi. b) Specimen labels. 4) Paralectotype from Grenada. a) Ventral habitus. b) Specimen labels. Photographs courtesy of Keita Matsumoto, NHMUK.

Figures 7–8. Psephenops smithi Grouvelle (=Xexanchorinus latus Grouvelle, jr. syn.), adult females. 7) Lectotype from Grenada. a) Dorsal habitus. b) Specimen labels. 8) Paralectotype from Grenada. a) Ventral habitus. b) Specimen labels. Photographs courtesy of Keita Matsumoto, NHMUK.