Dineutus solitarius Aube , 1838

Gustafson, Grey T. & Miller, Kelly B., 2015, The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera, Gyrinidae, Gyrininae, Dineutini), ZooKeys 476, pp. 1-135 : 73-75

Dineutus solitarius Aube, 1838 Figures 42, 43, 46, 51, 54

Dineutes solitarius Aubé 1838: 780, Dineutus (Cyclinus) solitarius : Hatch 1925b: 137, Dineutus solitarius : Leech 1940: 74, Dineutus (Cyclinus) solitarius : Leech 1948: 422, Dineutus solitarius : Arce-Pérez and Roughley 1999: 84.

Type locality.

Mexico, Veracruz

Specimens examined.

87

Type material examined.

Lectotype, here designated (1 ♂ male pinned) "MUSEUM PARIS/ VERA-CRUZ/ 1833 [beige label, typed black ink]// green disc [underneath is handwritten Veracruz/ 1883// in black ink]// solitarius [beige label, handwritten in black ink, handwriting appears to be Aubé’s]// TYPE [white label, typed red ink]// LECTOTYPE [red label, typed black ink]//" deposited in the MNHN.

Material examined.

COSTA RICA: Guanacaste: Santa Rosa N.P., 10°50.35'N, 85°37.07'W, 300 m, 6.vi.2008, leg. E. Nearns, I. Swift (2 ex. MSBA); 0.25km S Santa Rosa N.P., roadside pool, 15.vi.2003, leg. W.D. Shepard, EMEC 204684-204687; EMEC 204675 (5 ex. EMEC); La Pacifica nr Canas, 8.vi.1983, leg. J.E. Wappes, (1 ex. FSCA). EL SALVADOR: La Libertad: Hacienda Capolinas, 5 km NW Quezaltepeque, 455 m, 21.xii.1964, leg. M.E. Irwin (1 ex. UCRC). GUATEMALA: Jalapa: 4-7 km E. Jalapa, 12.vi.1991, leg. J.E. Wappes (1 ex. FSCA). HONDURAS: Comayagua: Malootal Minas de Oro, v.1932, leg. J.B. Edwards (3 ex. KSEM); Francisco Morazán: 4.5 km S.E. El Zamorano, 25.iv.1993, leg. I. Stange & R. Miller (1 ex. FSCA); La Paz: La Paz, 21.vii.1978, leg. V. Diaz, EMEC 204672 (1 ex. EMEC). MEXICO: Chiapas: 2.7mi W Colonia, Lazaro Cardenas, 6.viii.1965, leg. J.D. McCarty, EMEC 654699; EMEC 204761; EMEC 204769; EMEC 204777; EMEC 204801; EMEC 204807-204809 (8 ex. EMEC); 20 mi W of Cintalapa, 31.xii.1955, leg. J.C. Schaffner (2 ex. FSCA); Guerrero: Rincon, "kil.-256 S. MexCity", 31.x.1936, leg. H.D. Thomas (1 ex. KSEM); Jalisco: UNAM Biol. Sta. Chamela, 61 m, 9.viii.1982, leg. C.W. & L. O’Brien & G. Wibmer, at light (1 ex. FSCA); Est. Biol. Chamela, at lites, 13-22.vii.1992, leg. J. Chemsak, EMEC 204753; EMEC 204881; EMEC 204897; EMEC 204925 (4 ex. EMEC); 20 mi N Puerto Vallerta, “200”, 29.viii.1971, leg. J. Cicero (1 ex. FSCA); Nayarit: 7 mi. N Tetitlan, 14.vi.1962, leg. D.H. Janzen, EMEC 204772-204773; EMEC 204786; EMEC 204800; EMEC 204805-204806; EMEC 204857-204858; EMEC 204917-204920 (11 ex. EMEC); El Pichon, 25.vi.1963 (1 ex. FSCA); Jesus Maria, 26.vi.1955, leg. B. Malkin, EMEC 204804 (1 ex. EMEC); Sierra Zapotan, 1300 m, iii.1943, leg. E. Paredes (3 ex. UCRC); 24 mi SE Tepic, 1045 m, 22.vi.1968, leg. A.R. Hardy, L. Espinosa, J.P. Abrayaya (2 ex. UCRC); 20.3 mi W Compostela, 60 m, 19.vi.1967, leg. A.R. Hardy (1 ex. UCRC); Nuevo León: 10km N Linares, mercury vapor lamp, 430 m, 23.iii.1991, leg. R. Brooks, R. Leschen, Coll. No. 58 (1 ex. KSEM); Oaxaca: 5 mi N La Ventosa, 4.vii.1970, leg. R.E. Beer & party (3 ex. KSEM); 80km N of Arriga,10.vi.1971, leg. S.R. & L.M. Steinhauser (2 ex. FSCA); Quintana Roo: 10.9km S Playa del Carmen,1.vii.1990, leg. M.C. Thomas, (1 ex. FSCA); Isla de Cozumel, SW side 2mi W Cedral, 8.x.1993, leg. C.B. Barr & W.D. Shepard, EMEC 654700 (1 ex. EMEC); San Luis Potosí: El Salto Falls, 15.vi.1956, leg. R.E. Beer & party (5 ex. KSEM); El Salto, 19.vi.1953, Univ. Kans. Mex. Expedition (2 ex. KSEM); same as previous except: 488 m, 24.viii.1954 (1 ex. KSEM); same as previous except: 381 m, 4.ix.1962, leg. Ordway & Marston, at light (1 ex. KSEM); Sinaloa: Culiaoan, 6 mi S, Black & White lights, 6.viii.1964, leg. J.A. Chemsak & J. Powell, EMEC 204803 (1 ex. EMEC); 5 mi N Mazatlan, at light, 11.x.1975, leg. J. Powell, J. Chemsak, T. Friedlander, EMEC 204778 (1 ex. EMEC); 15 mi SE Mazatlan, 27.vii.1973, leg. J. Chemsak, E.G. Linsleys & A.E. Michelbacher, EMEC 204779 (1 ex. EMEC); Veracruz: 15mi NW of Acayucan, 18.vi.1958, leg. J.C. Schaffner, (1 ex. FSCA); Palma Sola, "255 Pastizal", 23.viii.1973, leg. G. Halffter & P. Reyes, Blacklight trap (1 ex. FSCA); 6mi SE Rinconada, 21.vi.1962, leg. D.H. Janzen, EMEC 204921 (1 ex. EMEC). NICARAGUA: Rivas: E of Lago de Apanás, 13°12.77'N, 86°58.06'W, 966 m, 12.vi.2005, leg. W.D. Shepard, EMEC 204676-204683 (8 ex. EMEC); Jinotega: roadside pool, Lago de Apanás area, N Jinotega, 13°12.8'N, 85°58.1'W, 966 m, 12.vi.2005, leg. C.B. Barr, EMEC 204673-204674 (2 ex. EMEC). U.S.A.: California: Riverside Co., Mecca, 15.viii.1924, EMEC 654698 (1 ex. EMEC); Texas: “Pinto”, 7.vii.1938, leg. D. W. Craik (1 ex. KSEM).

Diagnosis.

Male (Fig. 42C-D): Size: 9.2-10.4 mm. Body form broadly oval; elytral apices regularly broadly rounded, with serrations and irregularities absent apically, elytra reticulation normally coarse and well impressed laterally, medially being replaced by fine microreticulation, elytral disc medially often with fine and weakly impressed punctures, striae very faintly present, most evident medially on elytral disc; profemora with small sub-apicoventral tooth atop profemoral carina; protibiae weakly subsinuate to club-shaped; mesotarsal claws (Fig. 43C) with ventral margin straight, with weak medial expansion; venter darkly colored, usually black to very dark reddish brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 43A, B, D) median lobe in dorsal view just shorter than parameres, mildly parallel sided, weakly angled towards apex, acuminate in apical 1/5, apical median lobe angled towards acumination, lateral margins of acumination angled toward apex, apex very shortly rounded producing a strong point, in lateral view median lobe evenly shallowly curved dorsally, ventrally median lobe with diamond shaped sperm-groove, parameres in dorsal view weakly expanded laterally at apical 1/3, narrowly rounded apically.

Female (Fig. 42A-B): Size: 9.1-10.2 mm. Body form regularly oval; elytral apices regularly broadly rounded, with serrations and irregularities absent apically, apicolateral sinuation absent, elytra reticulation course and well impressed laterally, medially being replaced by fine microreticulation, elytral disc medially often with fine and weakly impressed punctures, striae very faintly present, most evident medially on elytral disc; profemora without sub-apicoventral tooth; protibiae club-shaped; venter darkly colored, usually black to very dark brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen.

Differential diagnosis.

Dineutus solitarius is unique among all other North American Dineutus in being smaller in size (9.1-10.4 mm), with a broadly oval body form (Fig. 42C), having the elytral apices broadly rounded without serrations and/or irregularities, males with the profemoral sub-apical ventral tooth small and atop a carina, and by the form of the aedeagus (Fig. 43A). The species most similar to Dineutus solitarius are Dineutus carolinus and Dineutus emarginatus . Both sexes of Dineutus solitarius can be distinguished from Dineutus carolinus in having the elytral apices broadly rounded without apical serrations and/or irregularities, as opposed to having the elytral apices narrowly rounded with serrations and/or irregularities present. The body form of Dineutus solitarius is much more regularly oval as opposed to being more elongate overall in Dineutus carolinus . Dineutus solitarius lacks a defined lateral marginal depression as seen in Dineutus carolinus as a result of being more dorsoventrally convex.

Of the two species similar to Dineutus solitarius , Dineutus emarginatus is more similar, in that both of these species have the elytral apices fairly broadly rounded and without apical serrations and/or irregularities present. Furthermore, the aedeagi of these two species are somewhat similar both being acuminate. In general both sexes of Dineutus solitarius can be distinguished from Dineutus emarginatus in being much more regularly rounded in body form than Dineutus emarginatus , whose body form is more elongate oval. The pronotal shape of the two species differs fairly noticeably, in Dineutus solitarius the pronotum has the lateral borders much more obtusely angled posteriorly to anteriorly, and the posterior margin of the pronotum flatly meets the posterolateral corners of the pronotum, while in Dineutus emarginatus the pronotum has the lateral borders more straightly angled posteriorly to anteriorly with the posterior margin being more sinuate.

Males of Dineutus solitarius can further be removed from Dineutus emarginatus in having a small profemoral sub-apicoventral tooth atop a carina, while in Dineutus emarginatus the tooth is much more large and triangular. The aedeagi of these two species are similar in that both have an acuminate median lobe, however the general shape of the median lobe of the two aedeagi can be separated without difficulty. The median lob of Dineutus solitarius (Fig. 43A) is much more parallel sided, being weakly narrowed towards the acumination and the acumination itself having its margins angled towards the apex, which is very narrowly rounded giving it a very pointed feel. In Dineutus emarginatus the median lobe (Fig. 20A) is weakly constricted medially giving the lateral margins a slight sinuation, the apical margins of the median lobe are rounded towards the acumination, with the acumination having its lateral margins fairly straight, and the apex relatively more broadly rounded, giving it a more rounded pointed shape, as opposed to narrowly pointed as in Dineutus solitarius .

The females of Dineutus solitarius differ primarily in the general differences between the two species.

Distribution

(Fig. 54B). From extreme southern United States, Texas ("Pinto Texas" 1938 [KSEM]) and California ( Leech 1940; Leech 1948), throughout Mexico ( Ochs 1949) and Central America to western Costa Rica. The first author visited the only known California locality, the city of Mecca, in Riverside County, in southwestern California, in the summer of 2012, in an attempt to recollect this species. The area had changed quite a bit with much of the duck ponds in the area having dried up and an increased agricultural presence was evident.

Habitat.

This species appears to be lotic. Several locality labels list "pools in stream". In La Selva Negra, Nicaragua, specimens were collected from a pool within a stream by the second author.

Discussion.

It should be noted that Dineutus solitarius is primarily a Mexican and Central American species, only just barely reaching the United States. Historical records indicate it was at one point found in California ( Leech 1940) and Texas.

There is some noticeable variation in the elytral sculpturing among populations of Dineutus solitarius . Specimens from Sierra de Zapotan, Nayarit, Mexico (UCRC) have the punctures of the elytra much more shallowly and weakly impressed, making them much larger and “dimply” in appearance (Fig. 46B). This is most noticeable medially on the elytra discs near the sutural region, where the strong lateral reticulation is replaced by the fine mesh microreticulation. Interestingly a similar situation is seen in specimens from the same area of Dineutus sublineatus (Fig. 46A). These specimens with the dimply punctation make it apparent that the fine weakly impressed punctation seen normally medially on the elytral discs is also present laterally, but is obscured by the strong reticulation of that area, and is visible medially and suturally due to the fine microreticulation of that area. Specimens from Costa Rica (MSBA) also show variation in elytral sculpturing, having the reticulation of the elytra composed of much finer meshes. The lateral meshes are still stronger but not nearly as coarse as in other populations. Specimens of Dineutus solitarius from Oaxaca, Mexico, near Arriba, (FSCA) show variation in body form. The outline of the body is much more broadly oval in these specimens. There is also a much greater dorsoventral convexity in the scutellar region, especially evident in lateral view. It should be noted that although there are these variations among populations, the aedeagi of males from each of these populations are not noticeably different or variable in any significant manner.

Type designation.

Similar to the situation with Dineutes metallicus Aubé, the only specimen with a date and Aubé’s handwriting for the determination label was selected as the lectotype (Fig. 51C). The other specimens in the MNHN collection lacked dates and/or Aubé’s handwriting, therefore we did not designate paralectotypes.