Giant water scavenger beetles Hydrophilus subgenus Dibolocelus (Coleoptera Hydrophilidae) from Mexico with description of two new species Arce-Pérez, Roberto Arriaga-Varela, Emmanuel Novelo-Gutiérrez, Rodolfo Navarrete-Heredia, José L. Zootaxa 2021 2021-09-01 5027 3 387 407 Arce-Perez & Arriaga-Varela Arce-Perez & Arriaga-Varela 2021 [151,997,330,357] Liliopsida Restionaceae Hydrophilus Plantae Poales 7 394 Tracheophyta species nucleoensis sp. nov. Dibolocelus   Figs. 5, 6; 15–18, 42   Etymology.This new species is named  H.( D.) nucleoensisbecause of its distribution on the Central American Nucleus, a natural area formed by mountain ranges that go from the center-south of the state of Chiapas in Mexico to the north of Nicaragua(see Halffter 1987; Halffter & Morrone 2017).   Type material (   31 ♂, 28♀). Holotypemale: MEXICO: Chiapas: Reserva Montes Azules[ 16°50′00″N 91°30′00″O],  14.vii.1989, F. Ariasy R. Barbacols. 1♂( CNIN).  Paratiposmismos datos que el holotipo 6♂, 4♀( CNIN); Ocosingo, Corozal, [ 16°49′16″N 90°53′25″O], 100 msnm  23.v.1984, E. Barreray A. Ibarracols. 5 ♂, 4 ♀( CNIN), Ocosingo, Boca Lacantún,  29.v.1984[ 16º34′ 50′′ N, - 90º 42′ 50′′O] 200 msnm, E. Barreray A. Ibarracols. 2 ♂, 2♀( CNIN);  24.v.1984, E. Barrera, A. Ibarray M. Garciacols. 1 ♂, 1♀( CNIN);  24.v.1984, A. Ibarracol. 1♂, 2♀( CNIN); Villa Flores, Villa Flores, [ 16°14′00″N 93°16′09″O], 500 msnm,  26.iv.1983, R. Fernándezcol. 1 ♂,  4.x.1983, E. Ríoscol. 1 ♂,  19.x.1983, J. Melchor 1 ♀,  8.xi.1983, S. Serranocol. 1 ♀,  13.xi.1983, C. A. col. 1 ♀,  3vii.1990, G. Moralescol. 1 ♂,  20.x.1999, Benjamin C. col. 1♀, Copainala, Copainala, 17° 06′ norte, 93° 17′ Oeste, 440 msnm,  16.v.1997, Arroyo, C. I. Sánchezcol. 1 ♀( IEXA); Palenque,  19.v.1984, [ 17°30′33″N 91°58′56″O], 60 msnm, A. Ibarray M. Garcíacols. 1 ♀( CNIN); Palenque Malla Bell,  20.iv.1988, J. Kemnercol. 1 ♀( IEXA), Acacoyagua, Acacoyagua, [ 15°21′00″N 92°41′00″O], 277 msnm,  i.1999, N. Jimenezcol. 1 ♀( IEXA), Mapastepec, Mapastepec, Rva. La Encrucijada, Laguna Chantutu, 28.viii,2000, 50 msnm, 15° 25′ 59″ Norte, 92° 53′ 52″ Oeste C. R. Chamécol. 1 ♀( IEXA). Campeche: Calakmul-Xpuhil[ 18°30′20″N 89°23′50″O],  29.v.2004, L. Cervantesy C. Mayorgacols. 1♂, 1♀( IEXA), Calakmul-Xpuhil, 200 msnm, 15/  17.xi.2001, E. Barreray H. Brailovskycols. 1♀( CNIN); Calakmul,  24.vii.2014, Selva Alta Perenifolia, Fernando Escobarcol. 1 ♂( IEXA); Guerrero: Hwy200, 5 mi. S. Tecpan, 17°11.2′N, 100 36.7′′ W,  30 m,  20.vi.2010, D.Brzoska 1 ♂( SEMC).  GUATEMALA. Escuintla:San José, [ 13°55′32″N 90°49′28″O],  4.i.1984, R. Pérezcol. 2 ♂; Escuintla, Río San José,  9.vi.1985, E. Pérezcol. 1 ♂( UVGC); Petén, San José,  October 1991, leg. Frisch, 1 ♂( SEMC).  NICARAGUA: Rio San Juan:Los Guatusos, río Pepaturro, [ 10°48′02″N 84°12′39″O], 21/  29.v.2000, B. Hernandez y J. Sunyer cols. 2 ♂; Río San Juan, Sarapiqui, 1/  5.ix.2006, A. Borges y P. Andino cols. 1 ♀; San Juan, San Carlos,  20.ii.1995, F. Collantescol. 1 ♀( IEXA).  COS- TA RICA: GuanacasteProv., Nandayure, nr. Carmona, 10°03′32.9′′N, 85°14′58.9′′W,  30 m,  15.i.2003, pond, leg. Short, Roughley, & Porras 1 ♂, 1♀( SEMC, INBio); Guanacaste Prov, Rdto Palo Verde, roadside ditch,  11.i2004, leg. Short& Lebbin,AS-04-027, 1 ♂( SEMC);  Limon Prov.,  Sector Cedrales de la Rita, 3 km N. Del Puente Rio Suerte, RutaPuerto Lindo,  November 1995, leg. E. Rojas, INBIO-CRI002-378269, 1 ♂( INBio).   Diagnosis.This species can be distinguished by the following combination of characters: Maxillary palpi clearly long and slender; fifth protarsomere as long as the basal ones together, flattened, with evident internal laminar expansion. This species is very similar to  H. ( D.) ovatusand  H. ( D.) pseudovatus  sp. nov.but can be distinguished from them by [the characters the characters of  H.( D.) ovatus and  H.( D.) pseudovatusare provided in brackets for comparative purposes] the maxillary palpi clearly longer and slender, width of the third pal- pomere 0.065 ( Fig. 15) [  H. ( D.) ovatusand  H. ( D.) pseudovatus  sp. nov.present maxillary palpi with the third palpomere flattened and widened, with width greater than 0.080 mm(Figs. 7,11)], fifth protarsomere flat and with evident internal laminar expansion ( Fig. 16) [without or with slight internal laminar expansion ( Figs. 8, 12)], abdominal ventrites 3 and 4 with slender glabrous area at midline ( Fig. 17) [ventrites 3 and 4 with wide glabrous area at mid-line ( Figs. 9, 13)], abdominal ventrites 3 and 4 raised and slightly acute above at midline ( Fig. 17) [ab- dominal ventrites 3 and 4 raised and flat above at midline ( Figs. 9, 13)];  H.( D.) ovatusand  H.( D.) pseudovatusare mainly distributed in the Neartic portion of Mexicowhile  H.( D.) nucleoensis  sp. nov.is mainly distributed in the Neotropical part of Mexico, extending towards Central America in Guatemalaand Nicaragua(Fig. 42).   Description male holotype.Body elongated-fusiform, length 32–37 mm(male holotype: 36 mm), width 17.0– 17.5 mmat humeri ( holotype: 17.0 mm), 2.1× 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 pale yellow; antennae, palpi and legs black with reddish hue ( Figs 5, 6).  Head: Antennae short with nine antennomeres, scape large and robust, longer than the next four antennomeres together, pedicel subequal to the following three antennomeres, sixth antennomere long and oval, subequal to the previous four together, not covering the first article of antennal club ( Fig. 15). Maxillary palpi long and slender, with four palpomeres, with lengths: 4.0, 3.1, 2.8, 1.6 mm; first palpomere small, sub-conical, second long, curved, slightly broadened towards apex, third shorter and wider, slightly flattened towards apex, with 0.060 mmin its wider side, fourth short, oval, with truncated apex. Mentum hexagonal, 1.7× wider at base than long, lateral margins parallel at basal half, apically converging straightly, apex truncated and straight. Labial palpi short, length of palpomeres: 0.02, 0.09, 0.06 mm; first palpomere very small and subconical, second long and slightly broadened towards apex, 1.2× longer than the third, with short golden setae near the internal margin, third palpomere short and oval, with apex rounded ( Fig. 15).  Thorax: Prosternal lobes raised and apically rounded, with short reddish-yellow setae at apex; mesoventrite with broad keel, with lateral margins rounded and convergent towards apex, with a broad and shallow concavity at basal half, deeper towards apex. Metaventrite with keel wide and flat, with feeble median longitudinal groove, ending as a long spine reaching half-length of the second abdominal ventrite ( Fig. 6). Each elytron with two well-marked rows of black spots, one sublateral starting after the humerus, and other more incomplete on the sides ( Fig. 5).  Legs: Anterior tibiae with two spurs; internal one shortest, flat, sub-rectangular with apex truncate straight; external spur longer, sub-triangular, acute; fifth protarsomere as long as the basal ones together, flattened, with evident internal laminar expansion; tarsal claws curved, without basal tooth, internal claw slightly longer than external one, protarsomeres 2–5 with tufts of golden setae in the external margin ( Fig. 16).  Abdomen: Vestiture leaving a long oval glabrous 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 apex slightly rounded and projected on the next ventrites. ( Figs 6, 17); ventrite 5 raised and slightly sharp above.  Genitalia: Total length 6.05 mm; phallobase long (length: 2.85 mm, width 2.25 mm) narrow with apex of manubrium rounded; parameres long (length: 4.25 mm), distinctly 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 ( 3.75 mm), broad sub-triangular, with a median sulcus, apex rounded ( Fig. 18 a, 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 32–37 mm, width 17.0– 17.5 mm, 1.8–2.0× longer than wide; body color can be dark brown with yellow-reddish hue (in old specimens); average length of maxillary palpomeres: 4.0, 3.0, 2.9 and 1.6 mm; average width of third maxillary palpomere: 0.65 mm; total length of labial palp: 1.8 mm.   Distribution. Mexico: Campeche, Chiapas, Guatemala: Escuintlaand Nicaragua: Río San Juan(Fig. 42). 1983-04-26 2014-07-24 1983-04-26 F, R, CNIN, E, A, M, J, S, C, G, I, IEXA, N, L, H, W, SEMC, UVGC, B, P, COS-, TA, RICA, INBio Reserva Montes Azules & Arias & Barba & Paratipos & Ocosingo & Corozal & Barrera & Ibarra & Boca Lacantun & Garcia & Villa Flores & Fernandez & Rios & Melchor & Serrano & Morales & Benjamin & Copainala & Arroyo & Sanchez & Palenque & Palenque Malla Bell & Kemner & Acacoyagua & Jimenez & Mapastepec & Laguna Chantutu & Chame & Calakmul-Xpuhil & Cervantes & Mayorga & Brailovsky & Calakmul & Selva Alta Perenifolia & Fernando Escobar & Hwy & Tecpan & D. Brzoska & Perez & Frisch & Collantes & Short & Lebbin & Sector Cedrales de la Rita Mexico Rva. La Encrucijada 30 10.059139 rio Pepaturro 1 -85.24969 Rio San Jose 7 394 INBIO-CRI002-378269 117 55 62 Rio San Juan holotype