Dineutus mexicanus Ochs, 1925

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 : 55-57

Dineutus mexicanus Ochs, 1925 stat. n. Figures 28, 29, 30, 51, 54

Dineutus truncatus mexicanus Ochs 1925: 13, Dineutus (Dineutus) truncatus mexicanus : Ochs 1926a: 138, Dineutus truncatus mexicanus : Blackwelder 1944: 81, Dineutus (Dineutus) truncatus mexicanus : Ochs 1949: 289, Dineutus (Cyclinus) truncatus mexicanus : Brinck 1955: 106, Dineutus truncatus mexicanus : Arce-Pérez and Roughley 1999: 84.

Type locality.

Mexico.

Specimens examined.

44

Type material examined.

Holotype (♂ with aedeagus dissected onto card point): “10393” [white label] // "Mexico Schl." [green label, handwritten in ink, handwriting unknown] // "Hist.-Coll. ( Coleoptera )/ Nr. 10393/ Dineutes spec./ Mexico, Schl./ Zool. Mus. Berlin" [green label] // " Dineutes truncatus / Sharp/ determ. Ahlwarth" [white label, part handwritten, determination portion typed]// "subspecies/ mexicanus / Type! Ochs 1924", [white label, appears to be hand written by Ochs (Horn and Kahle, 1990)]// "subsp. * / mexicanus / Ochs/ Mexico." [green label, hand written again by Ochs]// "HOLOTYPUS/ Dineutes truncatus / ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012" [red label, typed]// deposited in the ZMHB. Paratypes: (♀ specimen missing left protarsus): “10393” [white label]// "Hits.-Coll. ( Coleoptera )/ Nr. 10393/ Dineutes spec./ Mexico, Schl./ Zool. Mus. Berlin" [green label]// "? PARATYPUS/ Dineutes truncatus / ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012" [red label]//; (♀ specimen): “4” [white label, handwritten]// “85373” [white label, handwritten]// "Mochtlan/ Guerrero/ Baron" [white label, handwritten]// "Coll./ Harford", white label "B.C.A. Col. I. 2./ Dineutes / truncatus ,/ Sharp." [white label, handwritten except for determination]// " Dineutes truncatus / Sharp/ determ. Ahlwarth" [red label]// "PARATYPUS/ Dineutes truncatus / ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012" [red label]//; (♂ specimen): "Mexico/ J.Flohr G." [white label]// “94618” [white label, handwritten]// "Hist.-Coll. ( Coleoptera )/ Nr. 94618/ Dineutes truncatus Sharp/ Mixco, Juquila, Coll. Flohr/ Zool. Mus. Berlin/" [green label]// " truncatus / Sh" [white label]// "? PARATYPUS/ Dineutes truncatus / ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012" [red label]//; (A single right elytron, glued to card, specimen of unknown sex) “94618” [white label, handwritten]// "Mexico/ J.Flohr G." [white label, handwritten]// "Hist.-Coll. ( Coleoptera )/ Nr. 94618/ Dineutes truncatus Sharp/ Mexico, Juquila, Coll. Flohr/ Zool. Mus. Berlin" [green label]// "? PARATYPUS/ Dineutes truncatus / ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012" [red label]//; (♂ specimen headless): "Juquila/ 15" [white label, handwritten]//, “94618” [white label, handwritten]// "Mexico, J.Flohr G." [green label]// "Hist.-Coll. ( Coleoptera )/ Nr. 94618/ Dineutes truncatus Sharp/ Mexico, Juguila, Coll. Flohr/ Zool. Mus. Berlin" [green label]// "PARATYPUS/ Dineutes truncatus / ssp. mexicanus Ochs, 1925/ labelled by MNHUB 2012" [red label]// (6: ZMHB).

Material examined.

EL SALVADOR: Los Chorros Park, 16.vii.1961 (1 ex. UCRC); Chalatenango: San Jose del Sacare, 15.iii.1927, leg. R.A. Stirton (2 ex. KSEM); Tamanique: 1000 m, 8.xii.1972, leg. S. & L. Steinhauser (5 ex. FSCA); same as previous except: 3.vii.1972, leg. S. & L. Steinhauser (4 ex. FSCA). GUATEMALA: Zacapa: Sierra de los Minas, "El Naranjo", S slope below San Lorenzo Mine, 15.07329 -89.68481, 1600-1700m, 21-24.v.2010, leg. P. Skelley, oak forest at light (1 ex. FSCA). HONDURAS: "nr Progreso", Mico Quemado Mts, 6.xii.1958, leg. J.G. Matthysse, (2 ex. MSBA). MEXICO: Guerrero: Malinaltepec, Aserradero, 1500m, 2.xi.2000, leg. F. Pacheco, 24-8 (1 ex. IEXA); México: Villa Guerrero, Porfirio Díaz, Las Puentes, 14.iv.1990, leg. R. Arce, 7-4 (1 ex. IEXA); Michoacán: Chinicuila, Sierra de Coalcomán, La Nuez, Cañada El Colorín,, 15.ix.2003, leg. R. Novelo (2 ex. IEXA); same as previous except:16.ii.2005, leg. Gómex y Novelo, (2 ex. IEXA); Nayarit: 7mi N. Tetitlan, 14.vi.1962, leg. D.H. Janzen, EMEC 204752; 204756; 204853; 204856; 204866; 204894 (6 ex. EMEC); 8 mi SE San Blas, 27.vi.1967, leg. A.R. Hardy, (2 ex. UCRC); Oaxaca: San Juan Bautista Cuicatlán, Río La Concepción, 2.iv.1989 (4 ex. IEXA); km 84 carr 175 Oaxaca-Tuxtepec, 13.vi.1992, leg. R. Novelo (1 ex. IEXA); San José Independencia, Cerro el Vidrio, 1900 m, 25.v.2004, leg. G. Nogueira, (1 ex. IEXA); Veracruz: 6.vii.1965, leg. G.N. Ross, (2 ex. FSCA).

Diagnosis.

Male (Fig. 28C-D): Size: 14.5-16.8 mm. Body form regularly oval; elytral apices truncate, lateral corner of truncation distinctly angled, serration reduced to small pointed bumps and/or irregularities, apicolateral margin often faintly sinuate, elytral striae visible anteromedially near suture, disappearing laterally and prior to elytral apices, dense microreticulation covering much of elytra and pronotum; ulimate protarsomere (Fig. 30A) less than ca. 2 × as long as wide; protibiae club-shaped; profemora with small acute sub-apicoventral tooth; mesotarsal claw (Fig. 29C) with ventral margin with weak denticle; venter darkly colored, usually black to dark reddish brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 29A, B, D) with median lobe in dorsal view weakly constricted medially, being roundly expanded in apical 1/3, acuminate in apical 1/5, with apex broadly rounded, in lateral view, apex of median lobe broadly rounded, ventrally median lobe with parallel sided sperm-groove basally, being shortly expanded and rounded apically, parameres very weakly laterally expanded in apical 1/2.

Female (Fig. 28A-B): Size: 13.9-15.9 mm. Body form regularly elongate oval; elytral apices truncate, lateral corner of truncation distinctly angled, serration reduced to small pointed bumps and/or irregularities, apicolateral margin often faintly sinuate, elytral striae often indistinct, visible upon close examination, dense microreticulation covering entirety of elytra and pronotum, giving elytra and the pronotum a polished metal feel; ulimate protarsomere less than ca. 2 × as long as wide; protibiae club-shaped; profemora without sub-apicoventral tooth; venter darkly colored, usually black to dark reddish brown, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen.

Differential diagnosis.

Dineutus mexicanus is unique among all other North American Dineutus in having truncate elytra, with the lateral angle distinct, apicolateral sinuation weakly present, blunt serrations and irregularities present apically, males with a small acute profemoral sub-apicoventral tooth, and in the form of the aedeagus (Fig. 29A). The species most similar to Dineutus mexicanus is Dineutus truncatus (of which it used to be considered a subspecies of). The elytral truncature of Dineutus mexicanus differs in form having the apicolateral margin of the eyltra weakly sinuate, the lateral angle distinct, and the striae being more evident than those of Dineutus truncatus , especially in the males. There are also differences in body form discussed in the differential diagnosis section of Dineutus truncatus .

Males of Dineutus mexicanus can further be separated from Dineutus truncatus by the form of the protarsi (Fig. 30A), the mesotarsal claw shape, and the form of the aedeagus. See the differential diagnosis under Dineutus truncatus for details.

For females see the differential diagnosis section for Dineutus truncatus .

Distribution

(Fig. 54D). From Mexico to El Salvador ( Arce-Pérez and Roughley 1999; Ochs 1949).

Habitat.

Unknown. Most specimens observed for this study were old, collected during the late 1950's to the early 1970's containing only locality data and lacking habitat data. A single specimen from Guatamela was collected in 2010 with the habitat data given as "oak forest at light" (FSCA).

Discussion.

The elevation of Dineutus mexicanus to full species status was based on the noticeable and significant differences between the aedeagi of Dineutus truncatus and Dineutus mexicanus as well as the external characters discussed in the differential diagnosis section for Dineutus truncatus . These external characters include the protarsi, mesotarsal claws, and the elytral truncature, all found to be reliable indicators of species boundaries in North American Dineutus . The holotype (Fig. 51F) has been examined for this study allowing the characters of Dineutus mexicanus to be unambiguously known and the species status elevation to be embedded securely in accordance with differences found in the type.

The extent of the range of Dineutus mexicanus is currently unclear, due to the unclear identity of historical Dineutus truncatus records. For the current study the eastern most record of Dineutus mexicanus is from the Mico Quemado mountains near Progresso, Yoro, Hondoras (KSEM). Régimbart (1882) mentions a variety of Dineutus truncatus from Honduras, which Ochs (1949) now appears correct in that this record actually refers to Dineutus mexicanus . Specimens of Dineutus mexicanus for this study were also found in El Salvador, from several localities representing the southern-most confirmed record of Dineutus mexicanus . The western-most records for Dineutus mexicanus from this study are from Nayarit, Mexico, 8 miles southeast of San Blas. Confirmed specimens of Dineutus mexicanus are recorded from numerous records between these east and west localities including Guatemala, and the Mexican states of Veracruz, Oaxaca, and Guerrero. It is unclear how far north the range of Dineutus mexicanus extends in Central America and the Isthmus of Tehuanatepec. Based on the limited range data (Fig. 54D), it appears that Dineutus mexicanus may be a mountain endemic, following the Sierra de Madre de Chiapas through Chiapas, Mexico, Guatemala, and into El Salvador and Honduras, going northwest to southeast through its range. Therefore, Dineutus mexicanus may indeed be absent from the Northern Guatemala, Belize, and the Mexican states of Quintana Roo, Yucatan, Campeche, and Tabasco. In the west Dineutus mexicanus records again overlap with mountain ranges, being found in western Oaxaca in the Sierra Madre del Sur, going northwest along the western portion of the Trans-Mexican Volcanic Belt and into the Sierra Madre Occidental, as far north as Nayarit. Ochs (1949) lists a record for Tamaulipas, Mexico near Victoria, possibly for the Sierra Madre Oriental.