Hydrophilus (Dibolocelus) ovatus Gemminger & Harold, 1868

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 : 389-392

Hydrophilus (Dibolocelus) ovatus Gemminger & Harold, 1868

Figs. 1, 2 ; 7–10 , 41.

Hydrophilus ovalis Ziegler, 1844: 45 (primary homonym of Hydrophilus ovalis Brullé, 1837: 53 , and Hydrophilus ovalis Castelnau, 1840: 50 ).

Dibolocelus ovalis (Ziegler) ; Régimbart, 1901: 225.

Hydrophilus ovatus Gemminger & Harold, 1868: 476 (replacement name for Hydrophilus ovalis Ziegler ).

Stethoxus ovatus (Gemminger & Harold) ; Bedel, 1891: 314.

Hydrous (Dibolocelus) ovatus (Gemminger & Harold) ; Kuwert, 1893: 83.

Dibolocelus ovatus (Gemminger & Harold) ; Young, 1954: 196.

Studied material. United States of America: Louisiana, New Orleans , 26.vii.1959, At light, W. Gibson col. (3 ♂, 2 ♀) [ INIFAP] .

Diagnosis. This species is distinguished by the following combination of characters: maxillary palpi slender, third palpomere slightly flattened and broadened apically; internal protibial spur sub-rectangular with apex truncated, straight; fifth protarsomere robust, longer than basal ones together. Regarding the characters of body shape, color, vestiture, antenna, maxillary palps and male genitalia, the specimens of H. (D.) ovatus from North America, are very similar to those of H. (D.) pseudovatus sp. nov. from Mexico but can be distinguished by [characters of H. (D.) pseudovatus are provided in brackets for comparative purposes characters of H. (D.) pseudovatus ] third maxil- lary palpomere slightly flattened and broadened apically, with its internal margin slightly straight, maximum width 0.080 mm ( Fig. 7 ) [third maxillary palpomere markedly flattened and broadened toward the apex, with its internal margin slightly convex( Fig. 11 )]; fifth protarsomere longer and robust than the basal ones together ( Fig. 8 ) [fifth protarsomere shorter than basal tarsomeres together, flat and with a slight but evident internal laminar expansion ( Fig. 12 )]; the metaventral spine reaches or exceeds the posterior margin of the second abdominal ventrite ( Figs. 2 , 9 ) [short metaventrite spine, not exceeding 3/4 of the second abdominal ventrite ( Figs. 4 , 13 )]; ventrites 3 and 4 raised, with their apical margin slightly acute and slightly projecting over the next ventrite ( Fig. 9 ) [ventrites 3 and 4 slightly raised, with their apical margin slightly rounded and slightly projecting over the following ventrite ( Fig. 13 )]; ventrites with evident yellowish-reddish lateral oval spot [ventrites without spots].

Description. Body elongate-fusiform, length 30-33 mm, width 17-18 mm at humeri, 1.7-1.8× longer than wide, dorsally strongly convex and glabrous, ventrally flat and pubescent; body color black with dark greenish tone, ventrally black with red-yellowish hue, vestiture pale yellow; antennae, palpi and legs dark-reddish, the antennal club slightly lighter.

Head: Antenna short, scape large and robust, longer than the next four antennomeres together; pedicel subequal to the next three antennomeres; sixth long and oval with apex rounded, subequal to previous four together, not covering the first antennomere on the club ( Fig. 7 ). Maxillary palpi long and slender, with four palpomeres, with lengths: 0.4, 2.8, 2.66, 1.4 mm; first palpomere small, subconical; second long, curved and slightly broadened towards apex; third shorter, curved, slightly flattened and broadened towards apex, around 0.80 mm in its widest part, fourth short and oval, with apex truncated. Mentum broad, hexagonal, 1.8× wider at base than long, lateral margins parallel at basal half, apically converging straightly, apex truncated and straight; labial palpi short, length of palpomeres: 0.03, 0.08, 0.06 mm; first palpomere small and broad; second long and slightly broadened towards apex, 1.3× longer than the third and with short golden setae at inner margin near apex; third short and oval, with apex rounded ( Fig. 7 ).

Thorax: Prosternal lobes raised and apically rounded, with short reddish-yellow setae at apex; mesoventrite with keel wide, with lateral margins rounded and convergent towards apex, with a broad and shallow concavity at basal half, deeper near apex; metaventrite with a broad, flat keel with a median longitudinal groove, ending as a long spine reaching the posterior margin of the second abdominal ventrite ( Fig. 2 ). Elytra with four well-marked rows of small black spots, two on the disc, one sublateral starting after the humerus, and another one less complete on each side.

Legs: Anterior tibiae with internal spur short, flat, sub-rectangular with its truncated and straight apex, the longer external spur, acute sub-triangular; fifth protarsomere wide, and longer than the previous ones together. Tarsal claw long, curved and without a tooth in the base, internal claw little longer than the external. Protarsomeres 2─5 with tufts of golden setae in the outer edge ( Fig. 8 ).

Abdomen: Vestiture leaving a wide, long, oval glabrous area at mid-line in ventrites 3–4; and a broader subrectangular one in ventrite 5. Ventrites 3 and 4 raised and flattened above, with apex slightly acute and projected on the next ventrites. All ventrites bearing a yellow-reddish oval spot on each side ( Figs 2 , 9 ).

Genitalia: Total length 5.4 mm; phallobase long, (length: 2.7 mm, width: 2 mm), widest at union with parameres, manubrium slender with apex rounded. Parameres long (3.95 mm), very wide at basal 3/5, and elongated oval in their 2/5 apical, with a wide and deep oval concavity not reaching apex, and with minute teeth in the internal margin at the apical half, getting more abundant apically. Median lobe slightly shorter than parameres (3 mm), wide, sub-triangular, with a longitudinal median groove, and apex rounded ( Fig. 10 a, b ).

Sexual dimorphism. Female specimens are similar to males but with maxillary palpi narrow, tibiae with long sub-triangular spurs, tarsal claws curved and acute, with an acute basal tooth.

Distribution. The reported distribution of this species includes the United States of America, Southern Canada and Mexican states Chiapas, Michoacán, Nayarit, Quintana Roo, San Luis Potosí, Tamaulipas and Veracruz ( Smetana 1988; Short & McIntosh 2014) (Fig. 41). Nevertheless, in the present work we found no additional specimens from Mexico among the studied material and the description is based on specimens collected in USA.

Taxonomical comments.Andrew E.Z. Short (SEMC) (personal communication), noticed the existence of specimens from Veracruz of H. (D.) ovatus that show a certain degree of intergradation with H. (D.) pseudovatus sp. nov. in regards to the protarsomeres of males where the articles are slightly flattened, although not completely forming a laminar expansion as in the new species. Extensive additional sampling in Mexico and analysis of the genetic information of these population is needed in order to better elucidate the status of these two species.

Figures

FIGURES 1–6. Dorsal and ventral view of Hydrophilus (Dibolocelus) spp. 1–2 H. (D.) ovatus Gemminger & Harold; 3–4 H. (D.) pseudovatus sp. nov.; 5–6 H. (D.) nucleoensis sp. nov.

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.