Hydrophilus (Dibolocelus) cf. purpurascens ( Régimbart, 1901 )

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 : 403-404

Hydrophilus (Dibolocelus) cf. purpurascens ( Régimbart, 1901)

Figs. 23, 24 ; 33–36 , 42.

Dibolocelus palpalis var. purpurascens Régimbart, 1901: 223 .

Hydrous (Dibolocelus) palpalis var. purpurascens (Régimbart) ; Zaitzev, 1908: 367.

Hydrophilus palpalis s. purpurascens (Régimbart) ; Blackwelder, 1944: 171.

Dibolocelus purpurascens Régimbart ; Bachmann, 1969: 284.

Studied material (7♂, 4♀): Mexico: Veracruz: Alvarado, La Barranca, Rancho la Fiaca , 14.iv.2001, M . Aragón col. 1 ♂ ( IEXA) . Nicaragua: León, luz UV . 23.i.1993, Pogatshnik col 1 ♂; León , V-1988 , Maes col. 1 ♂, 1 ♀; León , III-1990 , Garcete col. 1 ♀; León , vi.1989 , Maes col. 1 ♀ ( IEXA) ; Río San Juan: Los Guatuzos, Río Papaturro , 40 m, UTM 16 P 0712685-1220212 , 17 / 24.iii.2000, Maes, Sunyer y Hernández cols. 2 ♂, 1 ♀; Río San Juan, San Carlos 21.ii.1995, F . Collantes col. 2 ♂.

Diagnosis. This species can be distinguished by the following combination of characters: Maxillary palpi robust, inflated, with third palpomere with a deep ventral excavation; anterior margin of mentum truncated and straight; anterior tibiae with a row of hard setae that form a subrectangular plate (comb-like) near the internal base ( Fig. 34 ); fifth protarsomere about as long as basal ones together, slightly flattened, without laminar expansion. This species is very similar to H. (D.) pollens but can be distinguished by [the characters of H. (D.) pollens are provided in square brackets for comparative purposes] H. (D.) cf. purpurascens being dorsally dark green with purple reflections ( Fig.23 ) [is dorsally black with greenish hue ( Fig. 21 )]; anterior margin of mentum truncated and straight ( Fig. 33 ) [anterior margin of mentum rounded ( Fig. 29 )]; protarsal claws not expanded, only acute ( Fig. 34 ) [claws expanded to 2/5 apical and apically acute ( Fig. 30 )]; metaventral spine longer, reaches or exceeds the posterior margin of the third abdominal ventrite ( Figs. 24 ) [the metaventral spine shorter, not exceeding 1/2 of the third abdominal ventrite ( Fig. 22 )]; ventrites 4 and 5 with a thick and glabrous crest ( Fig. 35 ) [ventrites 3 to 5 with a sharp and glabrous crest ( Fig. 31 )]; parameres thick, slightly directed outward and with apex broad sub-triangular ( Fig.36 ) [slender param- eres, slightly directed inward and with their apex truncated and directed inward ( Fig. 32 )].

Description. Body elongated-fusiform, length 33–38 mm, width 17–18 mm at humeri, 2.0× longer than wide, dorsally strongly convex and glabrous, ventrally flat and pubescent. Dorsal color black with dark purple tone (purple tone was not observed clearly in old specimens), ventrally black with reddish hue, ventral vestiture pale yellow; antennae, yellow, palpi yellowish-red, legs black with reddish hue ( Figs 23, 24 ).

Head: Antennae short with scape large and robust, slightly flattened, longer than the next four antennomeres together, pedicel subequal to the following three antennomeres together, sixth antennomere long and oval, with external margin subequal to the previous four together, almost completely covering the first article of antennal club. Maxillary palpi long and slender, with four palpomeres with lengths: 0.5, 2.8, 2.3, 2.1 mm; first palpomere small and globose, second robust, markedly curved and broadened towards apex, third globose, about 2.1× longer than wide, wider at basal third, with a deep and broad ventral excavation from base to near apex, fourth short, slender, subcylindrical, slightly curved and with truncated apex. Mentum hexagonal, 1.6× wider at base than long, lateral margins parallel, anterior margin slightly curved inwards, apex truncated and straight. Labial palpi short, length of palpomeres: 0.2, 1.7, 1.2 mm; first palpomere very small and broad, second long, inflated, sub-triangular and widening apically, 1.4× longer than the third, with a tuft of long golden setae near the outer margin, third palpomere shorter, comparatively narrow with truncate apex ( Fig. 33 ).

Thorax: Prosternal lobes raised with apex with acute tooth directed ventrally, with short reddish-yellow setae near apex; mesoventrite with broad keel, with lateral margins slightly convergent towards apex, with a elongate-oval shallow concavity at basal 4/5, deeper towards apex. Metaventrite with keel wide and convex, with rounded lateral margins, ending as a long spine reaching the posterior margin of the third abdominal ventrite ( Fig. 24 ). Each elytron with two well-marked rows of black spots, one sublateral starting after the humerus, and other more incomplete on the sides ( Fig. 23 ).

Legs: Anterior tibiae with a row of hard setae that form a subrectangular plate (like comb) near the internal base; with internal one spur shortest, flat, sub-rectangular with truncate apex, external spur longer, sub-triangular, acute; fifth protarsomere about as long as basal ones together, slightly flattened, without projections; tarsal claws long, curved, without basal tooth, internal claw slightly longer than external one; protarsomeres 2, 3 and apex of 5 with tufts of golden setae in the external margin ( Fig. 34 ).

Abdomen: Vestiture leaving a slender oval glabrous area at mid-line in ventrite 4, and broader sub-triangular one in ventrite 5. Ventrite 4 with a wide keel in the posterior 3/4 projecting over next ventrite as a short spine; ventrite 5 with a slightly acute keel along all its length at mid-line ( Fig. 24 , 35 ).

Genitalia: Total length 4.7 mm (holotype); phallobase long (length: 2.75 width 1.6) narrow with apex of manubrium rounded; parameres long (length: 3.2 mm), broadened at basal 3/5, and markedly narrowed at apical 2/5, slightly directed outward, with apex comparatively wide and subtriangular; median lobe elongate sub-triangular, slightly shorter than the parameres (2.65 mm), apex rounded with an elongate sclerite at mid-line ( Fig. 36a, b ).

Sexual dimorphism. Females similar to males but with narrow maxillary palpi, third labial palpomere not inflated nor excavated, protibiae with internal spine not truncate, acute, slightly shorter than external. Tarsal claws curved and acute with an acute basal tooth.

Distribution: Costa Rica, Guyana, Mexico: Veracruz, Nicaragua: León, Río San Juan and Venezuela (Arce- Pérez & Morón 2013; Bachmann 1969; Maes 1989) (Distribution in Mexico: Fig. 42).

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.