Hydrophilus (Dibolocelus) violaceonitens Jacquelin du Val, 1857

Arce-Pérez, Roberto, Arriaga-Varela, Emmanuel, Novelo-Gutiérrez, Rodolfo & Navarrete-Heredia, José L., 2021, Giant water scavenger beetles Hydrophilus subgenus Dibolocelus (Coleoptera Hydrophilidae) from Mexico with description of two new species, Zootaxa 5027 (3), pp. 387-407 : 395-401

Hydrophilus (Dibolocelus) violaceonitens Jacquelin du Val, 1857 status restored

Figs. 19, 20 ; 25–28 , 37–40 , 43, 46–49.

Hydrophilus violaceo-nitens Jacquelin du Val, 1857: 49 .

Stethoxus (Dibolocelus) violaceonitens (Jacquelin du Val) ; Bedel, 1891: 314.

Hydrous (Dibolocelus) violaceonitens (Jacquelin du Val) ; Kuwert, 1893: 83.

Hydrophilus (Dibolocelus) smaragdinus Brullé. Syn. : Régimbart, 1901: 227.

Hydrophilus (Dibolocelus) smaragdinus Brullé (in part), Hansen, 1999: 162.

Type material. [ Studied through photographs] Female ? holotype, MNHN: “ Cuba / C. Chevrolat”, “Type”, “ Hydrophilus / violaceo-nitens ”, “ smaragdinus Br. / v. violaceo nitens Duv.”, “ MUSÉUM PARIS / 1922 / coll. L. Bedel”, “ HOLOTYPE ”, “ HOLOTYPE / Hydrophilus / violaceonitens Jacquelin du / Val, 1857” / “ MNHN, Paris/ EC11750/ [barcode]”. [Specimen is damaged; maxillary palpi, mesotarsi and left metatarsus are missing]

Additional material (19♂, 6♀). MEXICO: Campeche: Kalkiní, El Remate, [20°22’21’’N, 90°03’03’’O] 26.iv.1982, M . García col. 3♂, 2♀ ( CNIN); El Remate , entre raíces de manglar, 12.xii. 2020, S . Ospina col. 1♂ ( IEXA) ; Chiapas: Salto de Agua [17°33′00″N 92°20′00″O] iv.1907, C . C . Hoffmann col. 1♂ ( CNIN) ; Quintana Roo: Tulum [20°12′43″N 87°27′57″O],. xi. 1981, E . Pech col. 2♂ ( CNIN); Puerto Morelos, [20°51′13″N 86°52′31″O] Gasolinera , 10.vii.1983, O . Canul col. 2♂ 1♀ ( CNIN); El Naranjo, Selva alta, 7.vii.1985, A . Cadena y Conde cols. Noct. 1♀ ( IEXA); F . Carrillo Puerto, [19°34′43″N 88°02′43″O] Laguna Chunyaxche , 30.viii.1988, Fernán- dez y Barba cols. 1♂ ( CNIN); F . Carrillo Puerto, 2.x.1983, 1♂ ( IEXA); Puerto Morelos , [20°51′13″N 86°52′31″O 1.v.1982] V . Meléndez col. 1♂, 1♀ ( CNIN) ; Tabasco: Villa Hermosa, Macultepec [18°09′00″N 92°52′00″O], v.1953, J . Hendrichs col. 1♂ ( CNIN) ; Veracruz: Las Choapas, [17°54′00″N 94°05′24″O], 28.v.1976, E . Barrera col. 1♂, 1♀ ( CNIN); Las Choapas, 28.i.1980, Sánchez Aguilera col. 1♂ ( IEXA); Tecolutla, Flores Magón, [20°23′17″N 97°01′31″O], 13.x.2001, Cabrera col. 1♂ ( IEXA); Actopan , La Mancha [19°30′13″N 96°37′09″O], 24.v.2002, a la luz, R . Arce col. 1♂ ( IEXA); Mexico, Vera Cruz , Flohr / B . C . A. Col. I . 2. Hydrophilus violaceo-nitens, Jaquelin du Val 2 ♂ ( BMNH) . CUBA: Provincia Matanzas, Playa Girón, Martin Vyklicky leg. 19.v.2004 1♂ ( NMPC) .

Diagnosis. This species can be distinguished by the following combination of characters: Maxillary palpi long and narrow; anterior tibiae with internal spur sub-rectangular with bifid apex; fifth protarsomere shorter than basal ones together, without internal projection or expansion. This species can be distinguished from H. (D.) smaragdinus Brullé a species from South America with which it was synonymized until now, by [characters of H. (D.) smaragdinus provided in brackets for comparative purposes]: H. (D.) violaceonitens without setose patch in the apical region of hind tibiae of males ( Fig. 38 ) [ H. (D.) smaragdinus has a dense patch of short setae in the medial apical region of the posterior tibiae in males ( Fig. 40 )]; prosternal lobe sharply truncated apically ( Fig.37 ) [prosternal lobes apically acute ( Fig 39 )]; ventrites 3–5 raised but not forming a sharp keel ( Figs. 20 , 27 ), [ventrites 3–5 raised as a sharp keel]; fifth protarsomere with straight internal margin and with reduced number of suction cups ( Fig. 26 ) [fifth protarso- mere wide with rounded internal margin, and with numerous suction cups]; male genitalia wide, parameres broad, abruptly narrowed towards apexapically, with a long internal oval concavity in the apical third, and with subapical elongated-oval gonopore ( Fig. 28 a, b ) [male genitalia slender with narrow parameres gradually tapering towards apex, and apex slightly widened]. Additionally, among the Mexican species H. (D.) violaceonitens is externally more similar to H. (D.) nucleoensis sp. nov., but differs from it by [the characters of H. (D.) nucleoensis provided in square brackets for comparative purposes]: in H. (D.) violaceonitens the mentum is broad, with parallel lateral margins in the basal half and in the apical half markedly curved, the apical margin truncated and slightly concave ( Fig. 25 ) [mentum not wide, with lateral margins parallel and slightly curved in the basal half, apically markedly convergent, the apical margin truncated and straight ( Fig. 15 )]; fifth protarsomer shorter than the previous ones together and without internal projection ( Fig. 26 ) [fifth protarsomer as long as the previous ones together, flat and with an evident internal laminar expansion ( Fig. 16 )]; anterior tibiae with sub-rectangular internal spur with bifid apex ( Fig. 26 ) [anterior tibiae with sub-rectangular internal spur with straight and truncated apex ( Fig. 16 )].

Redescription. Body elongated-fusiform, length 33 mm, width 17 mm at humeri, 1.9× longer than wide, dorsally strongly convex and glabrous, ventrally flat and pubescent; dorsal color black with dark green hue; ventrally black with reddish hue, ventral vestiture reddish yellow; antennae and palpi reddish yellow, legs black with reddish hue ( Figs 19, 20 ).

Head: Antennae short with scape large and robust, longer than the next four antennomeres together, pedicel subequal to the following three antennomeres together, sixth antennomere long and oval, subequal to the previous four together, not covering the first article of antennal club. Maxillary palpi long and slender, with four palpomeres with lengths: 3.0, 2.8, 2.0, 1.5 mm; first palpomere small, sub-conical, second long, curved, slightly broadened towards apex, third similar to the previous one but shorter, fourth short, oval, with truncated apex. Mentum hexagonal, 2× wider at base than long, lateral margins parallel at basal half, apically markedly curved, apex truncated and slightly concave. Labial palpi short, length of palpomeres: 0.2, 0.8, 0.6 mm; first palpomere very small and subconical, second long and slightly broadened towards apex, 1.3× longer than the third, with short golden setae near the internal apex, third palpomere short and oval, with apex rounded ( Fig. 25 ).

Thorax: Prosternal lobes raised and apically obtusely truncate, with long reddish-yellow setae at anterior margin of apex ( Fig. 37 ); mesoventrite with broad keel, with lateral margins rounded and convergent towards apex, with a deep oval concavity at basal half, deeper towards apex ( Fig. 37 ) and with transverse striae. Metaventrite with keel wide and flat, with feeble median longitudinal groove, ending as a short spine reaching 3/4 of the second abdominal ventrite ( Fig. 20 ). Each elytron with two well-marked rows of black spots, one sublateral starting after the humerus, and other incomplete on the sides ( Fig. 19 ).

Legs: Anterior tibiae with internal spur shortest, flat, sub-rectangular with apex bifid, external spur longer, sub-triangular, acute; fifth protarsomere shorter than basal ones together, without projections, tarsal claws curved, without basal tooth, internal claw slightly longer than external one, all protarsomeres with tufts of golden setae in the external margin, fifth protarsomere bearing a small apical ventral spine ( Fig. 26 ), hind tibia without setose patch ( Fig. 38 ).

Abdomen: Vestiture leaving a slender and long glabrous oval area at mid-line in ventrites 3–4; and a broader sub-rectangular one in ventrite 5. Ventrites 3 and 4 raised and slightly acute above, with its apex slightly acute and projecting over the next ventrite, ventrite 5 raised and subacute medially ( Fig. 27 ).

Genitalia: Total length 5.2 mm; phallobase long (length: 2.25, width 1.85 mm), narrow, with apex of manubrium rounded; parameres long (length: 4 mm), broadened at basal 3/5, elongated-oval at apical 2/5, with a deep oval concavity not reaching the apex, with minute teeth in the internal margin at the apical half, getting more abundant apically; median lobe slightly shorter than the parameres (3.7 mm), broad sub-triangular, with a median sulci, apex rounded ( Fig. 28a,b ).

Sexual dimorphism. Females similar to males but with narrow maxillary palpi, anterior tibiae with long subtriangular spurs, tarsal claws curved and acute, with and basal acute tooth.

Variation. Body length between 27–33 mm, width 16.5–17.5 mm, 1.8–1.9× longer than wide; dorsal body color from dark greenish to black, ventral color can be dark reddish to black, sixth antennomere and antennal club from reddish yellow to pitch black; average length of maxillary palpomeres: 3.0, 2.7, 2.0 and 1.4 mm; total length of labial palpi: 1.8 mm.

Taxonomic comments. This species was originally described by Jacquelin du Val (1845) from Cuba, and later recorded in Mexico by Sharp (1887) based on two specimens from Veracruz. Later Régimbart (1901) synonymized it under H. (D.) smaragdinus Brullé a species described from South America. Currently H. (D.) smaragdinus is recorded from several countries in the Neotropical Region: Bolivia, Brazil, French Guiana, Peru, Venezuela, Cuba and Mexico ( Bachmann 1968; Hansen 1999). Although, unfortunately we did not have the chance of directly studying the holotype deposited in Museum National d’historie Naturelle, Paris, we had access to high-definition photographs of the probably female holotype kindly provided by the curators of the museum ( Figs 46–49 ). After its study and the thorough examination of the morphology of the specimens from Veracruz studied by Sharp, multiple other specimens from Mexico, one recently collected specimen from Cuba, and its comparison with specimens of H. (D.) smaragdinus from Brazil and Venezuela (AOBC, NMPC), identified by A.O. Bachmann and Martin Fikáček respectively ( Figs 37–40 ), we conclude that the specimens from Cuba and Mexico are not conspecific with H. (D.) smaragdinus Brullé , therefore the restoration of H. (D.) violaceonitens as a valid species is fully justified. The present description of this species is based on a male from Mexico (Veracruz, La Choapas) compared to the material that Sharp (1887) cited from Veracruz and to a male specimens from Cuba (Matanzas, 1♂) and other specimens from Mexico.

Distribution. Cuba: Matanzas; Mexico: Campeche, Chiapas, Quintana Roo, Tabasco, Veracruz (Fig. 43)

Figures

FIGURES 19–24. Dorsal and ventral view of Hydrophilus (Dibolocelus) spp. 19–20 H. (D.) violaceonitens status restored; 21–22 H. (D.) pollens Sharp; 23–24 H. (D.) cf. purpurascens (Régimbart).

FIGURES 25–36. Morphological structures and male genitalia of Hydrophilus (Dibolocelus) spp. 25–28 H. (D.) violaceonitens sp. nov.; 25 ventral view of head (arrow: third labial palpomere); 26 protibia and tarsi, 27 ventral view of abdomen; 28a aedeagus ventral; 28b aedeagus dorsal; 29–32 H. (D.) pollens Sharp; 29 ventral view of head (arrow: third labial palpomere); 30 protibia and tarsi, 31 ventral view of abdomen; 32 aedeagus ventral; 33–36 H. (D.) cf. purpurascens (Régimbart); 33 ventral view of head (arrow: third labial palpomere); 34 protibia and tarsi (arrow: subrectangular row of hard setae); 35 ventral view of abdomen; 36a aedeagus ventral; 36b aedeagus dorsal.

FIGURES 37–40. Comparison of morphology between H. (D.) violaceonitens and H. (D.) smaragdinus Brullé (from Brazil); 37–38 H. (D.) violaceonitens status restored; 37 ventro-lateral view of pro- and mesothorax (arrow: apically truncate prosternal lobes); 38 ventral view abdomen and hind tibia (arrow: tibial apex without patch of setae); 39–40 H. (D.) smardagdinus Brullé (from Brazil); 39 ventro-lateral view of pro- and mesothorax (arrow: acute apex of prosternal lobes); 40 ventral view abdomen and hind tibia (arrow: patch of setae in tibial apex).

FIGURES 7–18. Morphological structures and male genitalia of Hydrophilus (Dibolocelus) spp. 7-10 H. (D.) ovatus Gemminger & Harold; 7 ventral view of head (arrow: third labial palpomere); 8 protibia and tarsi, 9 ventral view of abdomen; 10a aedeagus ventral; 10b aedeagus dorsal; 11–14 H. (D.) pseudovatus sp. nov.; 11 ventral view of head(arrow: third labial palpomere); 12 protibia and tarsi, 13 ventral view of abdomen; 14a aedeagus ventral; 14b aedeagus dorsal; 15–18 H. (D.) nucleoensis sp. nov.; 15 ventral view of head (arrow: third labial palpomere); 16 protibia and tarsi, 17 ventral view of abdomen; 18a aedeagus ventral; 18b aedeagus dorsal.

FIGURES 44–49. Type material and labels of Hydrophilus (Dibolocelus) from Mexico. 44 Specimen labels of Hydrophilus (Dibolocelus) pollens Sharp male lectotype (designated in this work); 45 Labels of female paralectotype; 46–48 Habitus of Hydrophilus (Dibolocelus) violaceonitens du Val; 46 dorsal; 47 ventral; 48 lateral; 49 Specimen labels of Hydrophilus (Dibolocelus) violaceonitens du Val holotype. Copyright of images 46–49 belongs to MNHN/Christophe Rivier.