Dineutus carolinus LeConte, 1868

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 : 29-36

Dineutus carolinus LeConte, 1868 Figures 10, 11, 53

Dineutus carolinus LeConte 1868: 366, Dineutes emarginatus var. carolinus : Régimbart 1882: 418, Dineutes carolinus : Roberts 1895: 283, Dineutus (Cyclinus) carolinus mutchleri Ochs 1924: 1 syn. n., Dineutus (Cyclinus) emarginatus carolinus : Ochs 1926: 136, Dineutus (Cyclinus) carolinus : Ochs 1929: 125, Dineutus carolinus : Ciegler et al. 2003: 15.

Type locality.

South Carolina.

Specimens examined.

199

Type material examined.

Dineutus carolinus LeConte, 1868: syntype (♀ pinned) "[orange disc]// Type/ 6093 [orange label Type typed in black ink, 6093 handwritten in black ink]// Dineutus carolinus / Lec. [white label handwritten in black ink, handwriting appears to be LeConte’s]// LECTOTYPE/ Dineutus carolinus / Desig. R.P. Withington III/ 1998 [red label, handwritten in black ink]//" deposited in MCZ.

Dineutus carolinus mutchleri Ochs, 1924: holotype (♂, pinned) "Nassau, Bahamas, V-VI-1917/Wm. M. Mann Collector//Amer. Mus. Nat. Hist., Dept. Invert. Zool., No.28070/HOLOTYPE/ Dineutus carolinus LeC. subsp. mutchleri OchsType! ♂/ Dineutus carolinus LeConte 1868. Det: L. Cook 2005" AMNH type catalogue No. 433.

Material examined.

BAHAMAS: Eleuthera Island: Rainbow Bay, 4.vii.1989, leg. D.B. & R.W. Wiley (1 ex. FSCA); Rainbow Bay, 21-28.iv.1984, leg. J.R. Wiley (6 ex. FSCA); Grand Bahamas Island: Freeport, 21.xii.1984, leg. S. Dunkle (4 ex. FSCA); Great Exuma: Simons Pt., “23.31.50-75.47.30”, 13.i.1980, leg. S.A. Teale (1 ex. KSEM); same as previous except: 21.i.1980 (1 ex. KSEM); same as previous except: 26.i.1980 (3 ex. KSEM); New Providence: 1.viii.1959, leg. J.B. Rearle (1 ex. FSCA); South Bimini: 14.vi.1967, leg. B.K. Dozier (2 ex. FSCA). U.S.A.: Arkansas: Washington Co., Devil’s Den State Park, pond, 6.viii.1975, leg. D. Huggins, SEMC 1054952 (1 ex. KSEM); Florida: Alachua Co., 10.ii.1949, leg. S.B. Mansell (5 ex. FSCA); same as previous except: 19.ii.1949, leg. B.W. Cooper (1 ex. FSCA); same as previous except: 8.iv.1949, leg. B.W. Cooper (2 ex. FSCA); same as previous except: 8.iv.1949, leg. E.H. McConkey (7 ex. FSCA); same as previous except: 19.iv.1949, leg. W.L. Jennings (1 ex. FSCA); same as previous except: 17.ii.1950, leg. O.G. Fogle (1 ex. FSCA); same as previous except: 15.iv.1950, leg. E.W. Michelson (1 ex. FSCA); same as previous except: 18.iv.1951, leg. J.E. Brogdan (1 ex. FSCA); same as previous except: x.1960, leg. S. Cabler (1 ex. FSCA); same as previous except: 4.ix.1989, leg. M.L. May (1 ex. FSCA); Gainesville, 20.iii.1987, leg. Willis, ACC.76-77; ACC.79-83; ACC.86; ACC.88 (9 ex. FSCA); Gainesville, 21.iii.1978, leg. L.R. Davis Jr., (2 ex. FSCA); same as previous except: 5.v.1978, leg. M.C. Thomas (1 ex. FSCA); same as previous except: 11.v.1978 (1 ex. FSCA); same as previous except: 2.vi.1978 (1 ex. FSCA); same as previous except: 18.iv.1983, leg. N. Hastettle (1 ex. FSCA); same as previous except: 5.vi.1983, leg. L.R. Davis Jr. (1 ex. FSCA); 5.vi.1959, leg. H.V. Weems Jr., taken at light (1 ex. FSCA); Gainesville, Beville Hts., 5.vii.1980, leg. L.A. Stange, Blacklight trap (1 ex. FSCA); NW Gainesville, 27.iii.1974, leg. J.B. Heppner, at blacklight (7 ex. FSCA); Gainesville, 3517 NW 10th Ave., 1.vi.1993, leg. R.E. Woodruff, Blacklight trap (8 ex. FSCA); 2 mi NW Gainesville, 20.iv.1974, leg. J.B. Heppner, blacklight (4 ex. FSCA); 6 mi SW Gainesville, 4.xi.1974, leg. L.R. Davis Jr., BLT (1 ex. FSCA); same as previous except: 5.xi.1974 (2 ex. FSCA); same as previous except:17.xi.1974 (1 ex. FSCA); same as previous except: 19.xi.1974 (2 ex. FSCA); Bainsville, 24.iii.1983, leg. C. Blare (1 ex. FSCA); Hatchet Creek, 25.vii.1975, leg. J.B. Heppner (3 ex. FSCA); O’Leno State Park, 8.viii.1997, leg. J. Cicero (3 ex. FSCA); Hogtown Creek, 28.vi.1975, leg. J.B. Heppner (1 ex. FSCA); Clay Co., Hibernia, 7.viii.1939, leg. J.D. Beamer (1 ex. KSEM); Collier Co., Copeland, 27.iv.1972, leg. H. Flaschka (1 ex. FSCA); Naples, 27.iv.1984, leg. R.A. Belmont, u.v. blacklight trap (1 ex. FSCA); Naples, 13.v.1984, leg. R.A. Belmont (4 ex. FSCA); Naples, 15.xii.1985, leg. R.S. Miller (1 ex. MTEC); Columbia Co., O’Leno State Park, 12.ii.1966, leg. F.W. Mead (1 ex. FSCA); O’Leno State Park,11.xii.1954, leg. C.N. Patton (1 ex. FSCA); Dade Co., nr Everglades Nat. Prk., fresh water, 7.v.1955, leg. D.K. Caldwell, K13 (8 ex. FSCA); Dade Co., Camp Mahachee, nr. Matheson Hammock, 27.iv.1983, leg. M.C. Thomas & L. Parker, Blacklight trap (2 ex. FSCA); Homestead, 28.v.1958, leg. D.O. Wolfenbarer, Blacklight trap (1 ex. FSCA); 25 m W Miami, 23.vii.1934, leg. P. McKinstry (1 ex. KSEM); 25 m W Miami, 23.vii.1934, leg. M.E. Griffith (1 ex. KSEM); Ross-Castello Hammock, 1.v.1968, leg. R.H. Arnett, Blacklight trap (1 ex. FSCA); Miami Springs,15.vi.1961, leg. C.E. White (1 ex. FSCA); Dixie Co., Horseshoe Beach, 28.vii.1985, leg. P. Van Mierop, pond (1 ex. FSCA); Escambia Co., Pensacola, 17.v.1960, leg. R.E. Woodruff, col. At light (1 ex. FSCA); Gadsden Co., Rocky Comfort Creek, 4 mi S Hwy 268,13.v.1980, leg. G.B. Wibmer, uv light (1 ex. FSCA); Gulf Co., St. Joseph T.H. Stone Memorial State Park, 14.vi.1969, leg. H.V. Weems Jr. (1 ex. FSCA); Henderson Co., Fletcher, 10.vii.1979, leg. L.L. Lampert, U.V. Light (1 ex. FSCA); Hernando Co., Weekiwachee Spring, 3.vi.1954, leg. W.C. Sloan, Sta.4 (2 ex. FSCA); Highlands Co., Archbold Biol. Sta., 7.iv.1975, leg. L.L. Lampert, UVL (1 ex. FSCA); same as previous except: 18.xi.1982, leg. L.L. Lampert Jr., UVL (1 ex. FSCA); same as previous except: 19.iv.1976, leg. L.L. Lampert Jr. (1 ex. FSCA); same as previous except: 23.vi.1988, leg. K.E.M. Galley, at blacklight SE tract (2 ex. FSCA); same as previous except: 19.iii.1968, leg. C.E. White, at blacklight trap (2 ex. FSCA); same as previous except: 10.ii.1993, leg. M.J. Rothschild (1 ex. FSCA); Highlands Co., Highlands Hammock State. Prk., 9-10.viii.1983, leg. K.W. Vick, Blacklight trap (1 ex. FSCA); same as previous except: 11.viii.1983 (1 ex. FSCA); Hillsborough Co., Hillsborough RI St. Pk., 9-10.viii.1983, leg. K.W. Vick, Blacklight trap (5 ex. FSCA); Plant City, 20.vi.1926, leg. C. O. Bare (1 ex. KSEM); Indian River Co., nr. Vero Beach, 12.iv.1983, leg. K. Hibbard (3 ex. FSCA); Lake Co., 26.iv., leg. E.M. Davis, (3 ex. FSCA); Leon Co., Springhill Rd., nr. Airport, 16.x.1980, leg. B. Lenczerski (1 ex. FSCA); Liberty Co., Yellow Creek SE of Telogia, 5.ix.1990, leg. F.N. Young, #3435 (1 ex. FSCA); same as previous except: 7.x.1992, #3503 (1 ex. FSCA); Torreya State Park, 16.v.1970, leg. H. Greenbaum, blacklight/sheet (1 ex. FSCA); Marion Co., 1-75 & Rte. 44, 12.iii.1988, leg. L.R. Davis Jr. & M. L. Benoit, at light (1 ex. FSCA); Village of Rainbow Springs, 3-7.vii.1982, leg. M.C. Thomas (2 ex. FSCA); Ocala, 5.viii.1975, leg. T. Rogers (1 ex. FSCA); Big Pine Key, 15.iii.1947, leg. L.D. Beamer (1 ex. KSEM); Okaloosa Co., 3 mi S. of Holt Log Lake Bridge, 4.x.1966, leg. P.A. Thomas (3 ex. FSCA); Palm Beach Co., 28.xi.1947, leg. McRae (1 ex. FSCA); Palm Beach Co., 3 mi N Bell Grande, 13.xii.1985, leg. R.S. Miller (2 ex. MTEC); Saint Lucie Co., White City,1.iv.1983, leg. K. Hibbard (2 ex. FSCA); U.S.A.: Georgia: Okefenokee Swamp, 30.vii.1934, leg. E. Griffith (2 ex. KSEM); same as previous except: 8.iii.1934, leg. P.A. McKinstry (1 ex. KSEM); Decantur Co., 1 mi W Recovery, 18.viii.1953, leg. F.N. Young, #986 (2 ex. FSCA); Kansas: Labette Co., Altamont, 5 mi E, Labette Creek, 22.vi.1974, SEMC 1054951 (1 ex. KSEM); Louisiana: St. John the Baptist, Edgard, 6.iii.1973, leg. V. Brou (2 ex. FSCA); same as previous except: 9.iii.1973 (1 ex. FSCA); same as previous except: 11.iii.1973 (2 ex. FSCA); same as previous except: 30.iii.1973 (1 ex. FSCA); same as previous except: 14.iv.1973 (2 ex. FSCA); 19.iv.1973 (1 ex. FSCA); same as previous except: 15.vi.1973 (2 ex. FSCA); same as previous except:13.vii.1973 (1 ex. FSCA); East Baton Rouge, Baton Rouge,19.x.1929, leg. H.A.S. (1 ex. MTEC); same as previous except: 31.vii.1961, leg. G.N. Ross (1 ex. FSCA); Madison, Tallulah, 7.vii.1930, leg. H. Mills (1 ex. MTEC); Maryland: Worcester Co., Pocomoke City, 22.ix.1984, leg. C.L. Staines Jr. (1 ex. FSCA); North Carolina: Carteret Co., Walker Mill Pond, 15.iii.1990, leg. J.B. Sullivan (1 ex. FSCA); Craven Co., North Harlowe, 18.vii.1990, leg. J.B. Sullivan (1 ex. FSCA); Jackson Co., Balsam, 2.v.1965, leg. W. Rosenberg (1 ex. FSCA); Oklahoma: Payne Co., nr Lake Carl Blackwell, 16.viii.1976 (1 ex. FSCA); Texas: Colorado Co., 3.iv.1922, leg. G. Wiley, "U of X Lot 1108" (3 ex. KSEM); Colorado Co., 18.v.1922, leg. G. Wiley (1 ex. KSEM); Montgomery Co., Woodlands, 2.vi.1979, leg. J.E. Wappes (3 ex. FSCA); same as previous except: 3.v.1980 (1 ex. FSCA); Walker Co., “Strawn”, 7.iii.1952, leg. T. Pyburn, "Green Branch" (1 ex. FSCA); Virginia: Middlesex Co., Warner, 13.x.1983, leg. C.L. Staines Jr. (1 ex. FSCA).

Diagnosis.

Male (Fig. 10C-D): Size: 9.1-10.9 mm. Body form elongate oval; elytral apices regularly rounded, with serrations and irregularities present apically, elytra with reticulation strong laterally and apically, medial disc with reticulation sparse or absent, striae faintly present, most evident medially on elytral disc, lateral marginal depression of elytra evident, narrow in humeral region, expanded posteriad, usually extending to lateral elytra apex; profemora with small sub-apicoventral tooth atop profemoral carina; protibiae subsinuate, distolateral margin flatly angled and weakly expanded; mesotarsal claws (Fig. 11F) with ventral margin weakly rounded; venter darkly colored, reddish brown to black, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen; Aedeagus (Fig. 11A) with median lobe in dorsal view nearly to as long as parameres, widest basally and regularly narrowed apically, more narrowed in apical 1/3, in some individuals much more noticeably narrowed in the apical 1/3, apex very shortly rounded, in lateral view median lobe sinuate ventrally in apical 1/3, parameres parallel-sided, broadly rounded apically.

Female (Fig. 10A-B): Size: 8.7-10.6 mm. Body form elongate oval; elytral apices regularly rounded, with serrations and irregularities present apically, apicolateral sinuation usually present, sometimes very strongly developed, elytra with reticulation strong laterally and apically, medial disc with reticulation sparse or absent, striae faintly present, most evident medially on elytral disc, lateral marginal depression of elytra evident, narrow in humeral region, expanded posteriad, usually extending to lateral elytra apex; profemora without sub-apicoventral tooth; protibiae weakly subsinuate, distolateral margin flatly angled; venter darkly colored, reddish brown to black, mesothoracic and metathoracic legs usually lighter in coloration, as well as apex of abdomen.

Differential diagnosis.

Dineutus carolinus is unique among North American Dineutus in having both sexes elongate oval and the elytra with a distinct lateral marginal depression, the elytral apices regularly rounded with serration and irregularities present, males with the profermoral sub-apicoventral tooth small and often atop a short carina, the male mesotarsal claws with the ventral margin rounded, and the unique shape of the aedeagus. The species most similar to Dineutus carolinus are Dineutus emarginatus , Dineutus solitarius , and Dineutus americanus .

Both sexes of Dineutus carolinus can be separated from Dineutus emarginatus by the elytra apices being more narrowly rounded with serrations and/or irregularities present. The presence of serrations, however, can be variable. In some individuals it is somewhat evident at the sutural margin, but others lack serrations entirely, having only roughened irregularities. The microreticulation of the elytra of Dineutus carolinus tends to be much more coarse laterally and the medial disk of the elytra often lacks reticulation, whereas Dineutus emarginatus tends to have fine microreticulation covering the entire elytra. Although not as reliable, the ventral coloration differs between the two species. In Dineutus carolinus the entire venter tends to be more reddish brown whereas it is regularly black in Dineutus emarginatus . The dorsal coloration of the two species is very similar.

Males of Dineutus carolinus can fairly easily be separated from Dineutus emarginatus by the profemoral sub-apicoventral tooth small atop a profemoral carina, rather than large and triangular. Also, in Dineutus carolinus the mesotarsal claws have the ventral margins rounded, rather than straight as in Dineutus emarginatus . The aedeagus is the best way to identify Dineutus carolinus . The median lobe of Dineutus carolinus is regularly narrowed for much its length, until the apical 1/3 where it is more strongly narrowed, but not strongly acuminate as in Dineutus emarginatus . Females of Dineutus carolinus are more difficult to separate from Dineutus emarginatus . The best way to distinguish them aside from the more narrowly rounded elytral apices with serrations and/or irregularities in Dineutus carolinus is the presence of an apicolateral sinuation in the elytra. This sinuation is nearly always present and well-developed in Dineutus carolinus , although in some females it is sometimes weakly developed or absent. Dineutus emarginatus females nearly always have this sinuation absent, but at most only weakly developed.

Members of Dineutus carolinus of both sexes can be distinguished from Dineutus solitarius by more elongate oval body form, the pronotum more narrow with the lateral margins more narrowly angled basally to apically, and the elytral apices more narrowly rounded apically with serrations and irregularities present. Dineutus carolinus of both sexes also have the lateral marginal depression of the elytra present, which is not evident in Dineutus solitarius . Males of Dineutus carolinus differ from those of Dineutus solitarius by the mesotarsal claws with the ventral margin curved, unlike Dineutus solitarius that have the ventral margins straight. The aedeagus of Dineutus carolinus is tapered but not acuminate, whereas that of Dineutus solitarius is acuminate. Females of Dineutus carolinus can also be separated from those of Dineutus solitarius by the apices of the elytra laterally sinuate, whereas in Dineutus solitarius they are usually evenly rounded without an apicolateral sinuation, and if a sinuation is present, it is very weakly developed.

Dineutus carolinus can be separated from Dineutus americanus by the differences provided under the differential diagnosis for Dineutus americanus .

Distribution

(Fig. 53A). Mainly known from the southeastern half of the United States ( Epler 2010; Folkerts 1978; Régimbart 1907; Roberts 1895), as far south as the extreme northeast corner of Mexico ( Wood 1962), and east into the Caribbean where it is primarily known from Nassau ( Young 1953), the range is here extended to the southeast as far as Great Exuma Island.

Habitat.

This species appears to be primarily lentic ( Young 1953, 1954). Dineutus carolinus occurs in Florida and is characteristic of small upland and flatwoods ponds, only rarely being found in slow streams with ample vegetation ( Young 1954). The first author has collected Dineutus carolinus in slow moving mud bottomed streams and bayous in southeastern Texas.

Discussion.

Dineutus carolinus is the only species of Dineutus well established across much of continental North America as well as in the western Caribbean where its range overlaps with that of Dineutus americanus . The two species are fairly similar.

The Caribbean subspecies Dineutus carolinus mutchleri was described by Ochs (1924), from Nassau (Bahamas), who used several characters to separate it from the mainland subspecies including, size and number of setigerous femoral punctures, as well as aedeagal shape. Size shows overlap and is not discrete. Number of setigerous punctures is known to vary among populations, especially with size (pers. obs.; Wood 1962). Ochs (1924) described differences in the aedeagus comparing it to the illustration provided by Roberts (1895), but the aedeagus of specimens examined from the Bahamas are identical to that of the mainland populations. We found the aedeagus of the Bahaman specimens to be nearly identical to those from mainland Florida and elsewhere (Fig. 11). Young (1953) also noticed the similarity and suggested that the drawing by Roberts (1895) was actually from an undescribed form in Texas. Ochs (1929) also mentions having compared the Bahaman specimens of Dineutus carolinus mutchleri to specimens of Dineutus carolinus from Texas, and that those showed greater differences than the Bahaman form.

Having examined some specimens of Dineutus carolinus from Texas (FSCA) there is some variation, but not much from other populations of Dineutus carolinus . A single male specimen examined from Texas has minor variation in the aedeagus from other mainland specimens (Fig. 11H), which may explain Roberts (1895) illustration. This specimen has the apical 1/3 of the median lobe more strongly narrowed (Fig. 11H) than other populations of Dineutus carolinus (Fig. 11A-E, G) from the mainland. The median lobe of the Texas Dineutus carolinus is nearly as long as the parameres, which are very parallel-sided and flatly rounded, similar to other populations of Dineutus carolinus (Fig. 11). Although Roberts (1895) illustration shows the strong narrowing, it also indicates the median lobe shorter than the parameres, which is not the case in our specimen. The parameres in Roberts (1895) illustration, however, match well with our specimen. Therefore, it may be that Roberts (1895) drew the aedeagus with the median lobe out of proportion, or, more likely, he drew the median lobe slightly flexed dorsally as happens sometimes during eversion or relaxing of the aedeagus. Externally the male from Texas is very similar to males of other populations. The females of Dineutus carolinus from Texas populations vary more so than male specimens from Texas, when compared to populations outside of Texas. The females are much more broad in appearance, having the pronotal and elytral margins more broadly rounded laterally. In lateral view the females are also slightly more dorsoventrally convex than other Dineutus carolinus females. The increased convexity of the elytra causes the lateral marginal depression to be more shallowly impressed in comparison to other populations. The microreticulation of the elytra also shows variation being much more well-impressed, covering nearly all of the elytra and the pronotum. The elytral apices of Texas Dineutus carolinus females are more broadly rounded and do not have the normal lateral sinuation seen in other populations, but have the apices laterally angled or simply regularly meeting the rounded apices, and the apical serrations and irregularities are highly reduced although, under careful observation, present. All of these variations, however, are well within the typical range of variation within other species of Dineutus and it is our judgment that the populations from Texas are not differentiated enough to merit a formal taxonomic name. The specimens examined from Texas were from the southeastern part of the state, in Montgomery County, near The Woodlands, north of Houston (FSCA).

Ochs (1929) also admits that after having examined more Dineutus carolinus from Florida and Georgia, that Dineutus carolinus mutchleri are much more similar to these populations of Dineutus carolinus than the Texas forms which he used as a comparison during description of Dineutus carolinus mutchleri . It does appear that the Texas specimens are the most distinctive of Dineutus carolinus populations, and the populations from the Caribbean formally named as a subspecies by Ochs (1924) are not, in fact, particularly distinctive. Therefore, based on examined specimens from Texas, southeastern U.S., and the Caribbean, we consider Dineutus carolinus mutchleri as a junior subjective synonym of Dineutus carolinus .