Dineutus discolor 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 : 37-41

Dineutus discolor Aube, 1838 Figures 14, 15, 51, 52

Dineutes discolor Aubé 1838: 784, Cyclous labratus Melsheimer 1846: 9 [synonymy by LeConte 1868], Dineutus discolor : LeConte 1863: 18, Dineutus labratus : LeConte 1863: 18. Dineutus discolor LeConte 1868: 367, Dineutus (Cyclinus) discolor : Hatch 1925b: 448, Dineutus (Cyclous) discolor : Hatch 1927: 27, Dineutes discolor : Leonard 1928: 262, Dineutus (Cyclinus) discolor : Hatch 1930: 20, Dineutus discolor : Omer-Cooper 1934: 6, Dineutus (Cyclinus) discolor : Brinck 1955: 106, Dineutus discolor : Ferkinhoff and Gundersen 1983: 15.

Type localty.

The United States of America

Specimens examined.

93

Type material examined.

Dineutus discolor Aubé, 1838: lectotype, here designated (1 ♀ pinned, missing right protarsus and right mesothoracic leg) "MUSEUM PARIS/ AMÉRIQUE SEPT./ AUDOUIN 1833 [beige label, typed black ink]// green disc [underneath is written in ink is 4117/ 33]// TYPE [white label, typed red ink]// LECTOTYPUS/ P. Brinck designavit 1955. [white label, typed black ink]// LECTOTYPE/ Dineutus discolor / Desig. RP Withington III/ 1998 [red label, handwritten in black ink]// LECTOTYPE [typed black ink]//" deposited in MNHN.

Material examined.

U.S.A.: Alabama: Marion Co., Barnsville, 23.viii.1931, leg. R.H. Beamer (1 ex. KSEM); Monroe Co., 10 km W Bowles, 31°33.094'N, 86°59.956'W, 11.v.2006, leg. K.B. Miller (1 ex. MSBA); Arkansas: Washington Co., Lake Sequoyah, 7.x.1992, leg. S. Garner (3 ex. MTEC); Florida: Holmes Co., Sandy Creek nr. Ponce de Leon, 11.vi.1978, leg. F.N. Young, #2756 (1 ex. FSCA); Santa Rose Co., Holly Creek at Rd. 260, 6.x.1966, leg. P.A. Thomas, (1 ex. FSCA); Georgia: Jackson Co., Allen Creek, S. Gainesville, 20.viii.1981, leg. F.N. Young, #2887 (1 ex. FSCA); Indiana: Putnam Co., Deer Creek, Manhattan, 19.viii.1969, leg. D.S. White (3 ex. FSCA); Maine: Oxford Co., Paris, 8.vii.1949, leg. C.R. Frost, 2674/ CAF’ 49 (1 ex. FSCA); York Co., Limington, Saco River, RT.11 at steep falls, 22.vi.1976 (1 ex. FSCA); Maryland: Patapsco River, 30.iv.1935, leg. W.L. Jellison (11 ex. MTEC); Prince George’s Co., Riverdale, 10.i.1910 (1 ex. MTEC) Montgomery Co., 2 mi. E. Silver Spring, N.W. Branch, 20.vii.1951, leg. G.H. Nelson (4 ex. FSCA); Massachusetts: Hampshire Co., Amherst, 24.vii.1967, leg. A Lavallee, (1 ex. FSCA); Norfolk Co., Dedham, 10.vi.1921, leg. G.C. Wheeler (1 ex. FSCA); Missouri: Reynolds Co., Sutton’s Bluff, 9.ix.1978, leg. K. Jackson, in creek (11 ex. FSCA); New Jersey: Raritan River Survey I, ACC Station 3B, 2.vii.1957, leg. T. Dolan (2 ex. KSEM); Middlesex Co., Avenel, 24.iv.1926, leg. Siepman (1 ex. KSEM); New York: New York, 8.v.1892, leg. E.O. Southwick, E.O. Southwick collection (1 ex. MTEC); Greene Co., East Durham, 26.vii.1971, leg. S.E. Thewke (1 ex. FSCA); Westchester Co., White Plains, 1.vi.1924, leg. E.H.P. Squire, (8 ex. FSCA); same as previous except: 8.vi.1924 (1 ex. FSCA); same as previous except: 10.vi.1923 (1 ex. FSCA); North Carolina: Macon Co., small pond in Wa tauga area n. Franklin, 26.vii.1986, leg. F.N. Young, #3118 (1 ex. FSCA); Moore Co., Mill Creek at Lake View, 7.ii.1966, leg. D.R. Paulson (1 ex. FSCA); Wake Co., 12.ix.1980, leg. R. Hollingsworth (3 ex. FSCA); Wake Co., Raleigh, leg. S.P. Whitney (4 ex. FSCA); same as previous except: 24.ix.1982, leg. R.H. Kenney (1 ex. FSCA); same as previous except: 12.ix.1984, leg. B.S. Bateman (1 ex. FSCA); same as previous except: 11.x.1984, leg. J.L. Williams (1 ex. FSCA); Wake Co., Raleigh, St. Road 1371, SW of Raleigh, 25.vii.1981, leg. S.P. Whitney, in stream (2 ex. FSCA); Rhode Island: Washington Co., Carolina, 24.ix.1970, leg. A. Lavallee (6 ex. FSCA); Kent Co., 1.ix.1969, leg. A. Lavallee (5 ex. FSCA); South Carolina: Aiken Co., Jackson, 4 mi NW at hwy 125 bridge, Holley Creek, 26.iii.1980, leg. D. Huggins, S. Hamilton, SEMC 1054961 (1 ex. KSEM); Tennessee: Cumberland Co., 8 mi S. Crossville, 26.vi.1962, leg. F.N. Young, #1968 (1 ex. FSCA); Maury Co., Colombia (1 ex. MTEC); Virginia: Albemarle Co., Charlottesville, 27.xi.1947, leg. H.H. Hobbs (1 ex. FSCA); West Virginia: Grant Co., 9 mi. SW Petersburg, 2.ix.1973, leg. J.B. Heppner (7 ex. FSCA).

Diagnosis.

Male (Fig. 14C-D): Size: 10.9-12.1 mm. Body form narrowly oval, attenuated anteriorly; elytral apices rounded with sutural angle produced into a point, rarely with point reduced and elytra appearing completely rounded, apicolateral sinuation present, serrations and/or irregularities absent, elytral striae very faint, most evident medially, elytra with fine microreticulation covering entirety, laterally microreticulation often coarser, medially with fine weakly impressed punctures; profemora with small weakly produced sub-apicoventral tooth; protibia weakly club-shaped, approaching subsinuate in large males, with distolateral margin weakly produced; mesotarsal claw as in Fig. 15C; venter lightly colored red to reddish orange; Aedeagus (Fig. 15A, B, D) median lobe in dorsal view parallel sided basally, weakly constricted medially, weakly narrowed in apical 1/3, apex obtusely rounded, in lateral view median lobe narrowed in apical 1/4, in ventral view sperm-groove parallel sided for near entirety of length, apex broadly rounded, parameres narrow, parallel sided, weakly arced basally to apically, apically very flatly rounded.

Female (Fig. 14A-B): Size: 10.6-12.8 mm. Body form narrowly oval, attenuated anteriorly; elytral apices rounded with sutural angle produced into a point, apicolateral sinuation present, serrations and/or irregularities absent, elytral striae very faint, most evident medially, elytra with fine microreticulation covering entirety, laterally microreticulation often coarser, medially with fine weakly impressed punctures; profemora without sub-apicoventral tooth; protibiae laterally weakly curved, distolateral margin weakly expanded; venter lightly colored, red to yellowish orange.

Differential diagnosis.

Dineutus discolor is unique among all North American species in the elongate oval and attenuate anteriorly body form, the elytra of both sexes with the apices rounded, with the sutural angle produced to a point with an apicolateral sinuation present, without serrations or irregularities present, a lightly colored venter, and males with the profemora with a small apicoventral tooth, and the form of the aedeagus (Fig. 15A). The species most similar to Dineutus discolor is Dineutus angustus . See the differential diagnosis under Dineutus angustus for separation of the two species.

Distribution

(Fig. 52D). Extreme southeastern Canada from Ontario to Nova Scotia ( Majka and Kenner 2009; Roughley 1991; Webster and DeMerchant 2012), and the eastern half of the United States ( Epler 2010; Ferkinhoff and Gunderson 1983; Folkerts 1978; Hilsenhoff 1990; Malcolm 1971; Régimbart 1907; Roberts 1895; Sanderson 1982; Wood 1962), south possibly into Mexico: Durango ( Ochs 1949).

Habitat.

Dineutus discolor appears to be strictly lotic, inhabiting streams ( Ferkinhoff and Gunderson 1983; Hilsenhoff 1990; Webster and DeMerchant 2012), and it has been suggested that this species prefers clear water ( Morrissette 1979). In Quebec Dineutus discolor was found in clear running water and in New Brunswick within embayments and along the margins of rivers ( Webster and DeMerchant 2012). In Florida, Young (1954) found Dineutus discolor to be a typical inhabitant of small streams in the uplands, avoiding the more acidic streams as well as the true flatwood streams within the state. Within streams Dineutus discolor swims in the current, moving upstream in quick jerks, allowing individuals to maintain their relative position in the stream among their aggregates, and swim downstream to dive and cling to submerged objects when alarmed ( Hatch 1925a). In more swift streams Dineutus discolor is often found in eddies behind objects obstructing the current, such as fallen logs, and may be restricted to these habitats ( Kolmes 1983a; Vulinec 1987). Stream dwelling Dineutus species also frequent areas where the current is slowed such as pools and wide meanders, avoiding torrential areas, riffles, and more swift currents ( Folkerts and Donavan 1973). Members of Dineutus discolor form rafts in areas of flowing water within the streams, with individuals keeping pace so as to remain in position in the raft, and the raft maintains its relative position within the stream ( Brown and Hatch 1929; Hatch 1925a). The first author has collected Dineutus discolor in both small pebble-bottomed forested streams as well as large mud-bottomed rivers in the southeastern United States. Both situations had clear water similar to situations described above and individuals collected from larger streams were found in areas with slowed water.

Discussion.

Dineutus discolor has an extensive range from the northern third of Florida up the Atlantic coast to Canada, and west to Iowa and Minnesota (Fig. 52D). The true extent of the western and southern boundaries of the range of Dineutus discolor seems somewhat uncertain. Ochs (1949) lists a single specimen of Dineutus discolor in his collection as having the label "Mexico, Durango".

Kolmes (1983b; 1985) discussed the precopulatory behavior of Dineutus discolor describing the interesting “Proleg-up” mate signaling used by females. Kolmes (1983a) also investigated aspects of prey capture within this species.

The larvae of Dineutus discolor have been found under stones within streams with adult Dineutus discolor at a depth of 20 cm to 60 cm in areas where water is flowing, but not so rapidly as to create breaks in its surface such as rapids ( Brown and Hatch 1929). Hatch (1927) included Dineutus discolor in a key to gyrinid larvae.

Type designation.

While several North American Dineutus specimens carry type designations by "RP Withington III", these were never published thus do not consistute viable nomenclatural acts according to Article 11 of The Code ( ICZN 1999). Among the material in the MNHN there are 4 other specimens designated by Withington III as paralectotypes, aside from the specimen here designated formally as the lectotype. Brinck also included a lectotype label on this specimen, but similarly, Brinck did not publish a written account of specimens he designated at the MNHN as lectotypes. The specimen selected here as the lectotype (Fig. 51B) has a locality label indicating the specimen is from the U.S. as well as a disc that allows the date and local to be checked in the MNHN’s registrar. Other specimens in the collection (including the unpublished paralectotypes designated by Withington) lack date indications. Therefore only the specimen with the date showing its collection prior to Aubé’s description, and being from the United States (as verified by the registrat at the MNHN) is safe to assume was a part of the original syntype series, and is here formally designated as the lectotype of Dineutus discolor . Given the uncertainty of the other specimens suggested to be paralectotypes by Withington III, it is our opinion that these specimens should not be regarded as paralectotypes.