Hydrophilus (Dibolocelus) pollens Sharp, 1887

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 : 402-403

Hydrophilus (Dibolocelus) pollens Sharp, 1887

Figs. 21, 22 ; 29–32 , 43.

Hydrophilus pollens Sharp, 1887: 762 .

Dibolocelus pollens (Sharp) ; Régimbart, 1901 b: 665.

Hydrous (Dibolocelus) pollens (Sharp) ; Zaitzev, 1908: 367.

Type material (1♂, 1♀): male lectotype, BMNH: B. C. A. Col. I. 2. Hydrophilus pollens, Sharp. / Sharp Coll. 1905- 313 / hoff / Mus. Laferté / Syntype / LECTOTYPE, Hydrophilus pollens Sharp, Arce-Pérez, Arriaga-Varela et al. Des. 2021 ; female paralectotype, BMNH: Hydrophillus pollens ♂ [not ♂ but ♀, H. S. 1933], Vera Cruz, Mexico. Höge / B. C. A. Col. I. 2. Hydrophilus pollens, Sharp. / [ovipositor in slide] ♀, TYPE ♀, end of ovipositor / Syntype / Type H. T, / LECTOTYPE Hydrophilus pollens Sharp 1887 , des. A. Short, 2004 / PARALECTOTYPE, Hydrophilus pollens Sharp, Arce-Pérez, Arriaga-Varela et al. Des. 2021 .

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 rounded. Fifth protarsomere shorter than basal ones together, without laminar expansion. Protarsal claws moderately long, curved, expanded at distal 2/5, apex markedly acute. This species is very similar to H. (D.) cf. purpurascens , but can be distinguished by [the characters of H. (D.) cf. purpurascens are provided in square brackets for comparative purposes] H. (D.) pollens being dorsally black with greenish hue ( Fig. 21 ) [dark green with purple reflections ( Fig.23 )]; anteri- or margin of mentum rounded ( Fig. 29 ) [truncated and straight ( Fig. 33 )]; protarsal claws expanded to 2/5 apical and apically acute ( Fig. 30 ) [claws not expanded, only acute ( Fig. 34 )]; the metaventral spine shorter, not exceeding 1/2 of the third abdominal ventrite ( Fig. 22 ) [metaventral spine longer, reaches or exceeds the posterior margin of the third abdominal ventrite ( Figs. 24 )]; ventrites 3 to 5 with a sharp and glabrous crest ( Fig. 31 ) [ventrites 4 and 5 with a thick and glabrous crest ( Fig. 35 )]; slender parameres, slightly directed inward and with their apex truncated and directed inward ( Fig. 32 ) [parameres thick, slightly directed outward and with apex broad sub-triangular ( Fig.36 )].

Redescription. Body elongated-fusiform, length 34–39 mm, width 15–16 mm at humeri, 2.2–2.3× longer than wide, dorsally strongly convex and glabrous, ventrally flat and pubescent; dorsal color black with dark green tone, more evident under direct light; ventrally black with reddish hue, ventral vestiture pale yellow; antennae, yellow, palpi dark yellowish-red, legs black with slight purplish hue, femora with dorsal surface and apices of ventral surface reddish ( Figs. 21, 22 ).

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, subequal to the previous four together, almost completely covering the first article of antennal club. Maxillary palpi long and robust, with four palpomeres with lengths: (0.5, 2.5, 2.1, 1.9 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 apex, fourth short, slender, subcylindrical, slightly curved and with truncated apex. Mentum hexagonal elongate, 1.5× wider at base than long, lateral margins parallel, anterior margin rounded. Labial palpi short, length of palpomeres: 0.2, 1.8, 1.1 mm mm; first palpomere very small and broad, second long, inflated, sub-triangular and widening apically, 1.6× longer than the third, with a tuft of long golden setae near the outer margin, third palpomere shorter, comparatively narrow with truncate apex ( Fig. 29 ). 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 rounded and rather parallel towards apex, with a long and shallow oval concavity in the basal 3/5, deeper towards the apex. Metaventrite with keel wide and slightly convex, with feeble median longitudinal groove, ending as a long spine reaching half-length of the third abdominal ventrite ( Fig. 22 ). Each elytron with two well-marked rows of black spots, one sublateral starting after the humerus, and other more incomplete on the sides ( Fig. 21 ).

Legs: Anterior tibiae with internal one spur shortest, flat, sub-rectangular with truncate and straight apex, external spur longer, sub-triangular, acute; fifth protarsomere shorter than basal ones together, slightly flattened, without projections; tarsal claws long curved, expanded into apical 2/5, then markedly acute, 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. 30 ).

Abdomen: Vestiture leaving a slender and long oval glabrous area at mid-line in ventrites 3–4; fainter in ventrite 3, and broader sub-triangular one in ventrite 5. Ventrite 3 raised and with a small glaborus line in posterior half, ventrite 4 with an acute keel in the posterior 3/4 projecting over next ventrite as a short spine; ventrite 5 with an acute keel along all its length at mid-line ( Fig. 31 ).

Genitalia: Total length 4.8mm (holotype); phallobase long (length: 2.3 width 1.2 mm) narrow with apex of manubrium rounded; parameres long (length: 4.2 mm), broadened at basal 3/5, and markedly narrowed at apical 2/5, directed internally, with apex truncate and; median lobe elongate sub-triangular, slightly shorter than the parameres, with an elongate sclerite at mid-line ( Fig. 32a, 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. Mexico: Veracruz (Fig. 43), Guyana.

Taxonomical comments. This species was described by Sharp (1887: 762), based on a very small number of specimens and diagnostic characters. Unfortunately, there are no recent specimens known, and our redescription is based only on the type material of H. (D.) pollens Sharp , deposited in the Natural History Museum of London (BMNH). This species and H. (D.) cf. purpurascens appear to be the only species in Mexico and Central America belonging to the group of species with the third maxillary palpomere inflated and a strong ventral concavity ( Figs. 29, 33 ). A female syntype has been previously labelled as the holotype apparently based on a misidentification of the sex of the specimen ( Fig. 45 ). Nevertheless, in the original description Sharp (1887) did not mention any specimen in particular as being the holotype. Additionally, this female syntype bears a lectotype label by Andrew E.Z. Short ( Fig. 45 ). This lectotype designation was, however, unpublished. Here we designate the male syntype as the lectotype in order to fix the identity of the species ( Fig. 44 ). A specimen from Demerara, Guyana was part of the original series studied by Sharp. Since it is a female its identity cannot be confirmed beyond a doubt as well as its relation to the Mexican specimens. Nevertheless, its identity preliminary remains as originally intended by Sharp. Other species from South America are probably close to H. (D.) pollens . On his treatment of Venezuelan Hydrophilus Bachmann (1969) illustrated the genitalia of H. (D.) purpurascens Régimbart and the figure suggest a very close resemblance to H. (D.) pollens . However, Bachmann (1969) did not study the type specimens of any of the species treated therein. Type series of H. (D.) purpurascens , held in MNHN, is composed of females or specimens with broken appendages, and its genitalia has not been studied (Andrew E.Z. Short personal communication). Similarly, the study of the types of H. (D.) palpalis viridis (Régimbart) (MNHN) suggest a strong external resemblance with H. (D.) pollens but its male genitalia have not yet been studied or illustrated (Andrew E.Z. Short personal communication). The nature of the relationship between these species remains to be solved through a detailed study of type specimens of South American species.

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 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.