Hydrochus variolatus LeConte 1852: 211 Hydrochus otvosi Makhan 1993: 67 Taxonomy of Central American water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae) Perkins, Philip D. Zootaxa 2021 2021-05-21 4974 3 459 503 3N6CY LeConte LeConte. The 1852 [151,528,582,609] Insecta Hydrochidae Hydrochus Animalia Coleoptera 22 481 Arthropoda species variolatus   Figs. 2, 17, 18, 26, 34      Hydrochus variolatus LeConte 1852: 211.     Hydrochus otvosi Makhan 1993: 67. New Synonymy.   Type material. There is only one specimenof  Hydrochus variolatusLeConte, a male, in the LeConte collection at the MCZ. It is therefore the holotype, by monotypy. Imagesof the habitus, male genitalia, and labels of this specimen given herein ( Figs. 18, 26). Originallydescribed from San Diego, California, the following new records are from Mexico.  Material examined (19):   Mexico: Baja California, 17 mi.S. of Ensenada,  14.vi.1938, leg. Michelbacher& Ross(9 CAS);  Norte, Arr. Santo Domingo, 5.7 mi. E. Hamilton Ranch,  23.iv.1963, leg. H. B. Leech, P.H. Arnaud, Jr.(4 CAS);  Norte, Sa. Juarez, 1 mi. S. Laguna Hanson, elev.  5000 ft,  19.vii.1970, leg. P. D. Perkins(1 MCZ);  San Jose del Castillo,  15.vi.1961, leg. E. L. Sleeper- 1 male(1 TAMU);  Campeche, Escarcega,  18.v.1962, leg. F. IslasS. (1 NMNH);  Jalisco, Chamela, Rio Chamela,  4.vi.1989, leg. G. Ortega(1 UNAM);  Veracruz, 9 mi. W. Poza Rica,  27.viii.1965, leg. Paul J. Spangler(1 NMNH);  Rio Metlaonr. El Fortin,  17.xii.1948, leg. H. B. Leech(1 CAS).   Differential diagnosis.Among Central American species, recognized by the combination of moderate size (ca. 3.10–3.46 mm), the deep pronotal depressions, the well raised and relatively impunctate pronotal reliefs, and the male genitalia ( Figs. 17, 18; described below). This species has a generalized  Hydrochushabitus; reliable determinations will require dissection of males. The male genitalia have a very large adbl, and a unique character: the adbl and the continuing shaft of the aedeagus are on the same plane for about 1/3 the length of the aedeagus; this is best seen in lateral view. Male genitalia ( Figs. 17, 18). General characters: paramere tips slender and pointed, narrower in lateral view than in dorsal/ventral views, in dorsal/ventral views with medial margins at apex parallel or nearly so, then weakly arcuate away from midline, plsa absent or very slight; aedeagus in dorsal/ventral views moderately wide, parallelsided or nearly so; in lateral view wider, especially basally, adbl and continuing shaft of aedeagus on same plane for about 1/3 length of aedeagus, after which shaft dorsal margin is sinuate; lateral margins of aedeagus sclerotized; basal piece shorter than parameres, orifice strongly sclerotized. Dorsal surface: pdmm sinuate, slightly overlapping aedeagus; adbl very large, ca. ½ as wide as total genitalia width at that level; adtl at about midlength of shaft; paramere tips without sclerotized ridge. Ventral surface: pvmm approximating lateral margin of aedeagus; avtl near base.   Remarks. I have examined the holotypeof  Hydrochus otvosiMakhan (HNHM), including the male genitalia, and have determined that it is a synonym of  Hydrochus variolatusLeConte. The  H. otvosi holotypespecimen is supposedly from Costa Rica. The non-type specimen of  H. variolatusimaged ( Fig. 17) has this locality data: Baja California, Norte, Sa. Juarez, 1 mi.S. Laguna Hanson, elev. 5000 ft, 19.vii.1970, leg. P. D. Perkins. 3128194508 Mexico California Images San Diego 22 481 1 holotype 3128194565 1938-06-14 CAS Michelbacher & Ross Mexico Ensenada 22 481 1 Baja California 3128194460 1963-04-23 CAS H. B. Leech & P. H. Arnaud Jr. Mexico Arr. Santo Domingo Norte 22 481 1 Baja California 3128194404 [293,1383,1040,1067] 1970-07-19 MCZ S. Laguna Hanson & P. D. Perkins Mexico 1524 Sa. Juarez Norte 22 481 1 Baja California 3128194377 1961-06-15 TAMU E. L. Sleeper Mexico San Jose del Castillo 22 481 1 1 Baja California 3128194305 1962-05-18 NMNH F. Islas Mexico Escarcega 22 481 1 Campeche 3128194407 [319,1094,1112,1138] 1989-06-04 UNAM G. Ortega Mexico Rio Chamela Chamela 22 481 1 Jalisco 3128194386 1965-08-27 NMNH W. Poza Rica & Paul J. Spangler Mexico Veracruz 22 481 1 Veracruz de Ignacio de la Llave 3128194433 [677,1390,1148,1175] 1948-12-17 CAS El Fortin & H. B. Leech Mexico Rio Metlao 22 481 1 Veracruz