Brachycentrus (Brachycentrus) nigrosoma (Banks 1905)

Brachycentrus (Brachycentrus) nigrosoma (Banks)

Sphinctogaser nigrosoma Banks, 1905:12.

Brachycentrus nigrisoma (Banks).—Banks, 1907b:42.—Ross, 1944:303.—Flint, 1966:386 [lapsus for B. nigrosoma].

Brachycentrus notabulus Milne, 1936:112, 123.—Fischer, 1970: 109.—Denning, 1971:209 [new synonymy].

Brachycentrus nigrosoma (Banks).—Fischer, 1970:108.

Brachycentrus adelus Ross, 1947:165.—Fischer, 1970:99 [new synonymy].

Although closely related to the European B. subnubilus Curtis, this is a distinctive species in the North American fauna both as an adult and larva. The larva possesses a distinctively different filtering fringe on the femora of the mid- and hindlegs. There are only two greatly enlarged setae, borne on the ventral margin, and the filtering setae are arranged in the manner of longer setae separated by a fanlike array of shorter setae. The gills are either lacking, or, when present, consist of stellate clusters of short filaments on the posterior margin of the abdominal terga.

The genitalia of the male are also quite distinctive. The cerci are short, and almost triangular in dorsal outline; the tenth tergal lobes are very short and only slightly bilobed in dorsal aspect; and the apex of the claspers in posteroventral aspect is slightly divided, almost like a fishtail in appearance.

ADULT.—Length of forewing, 7–8 mm, 9–10 mm. Color grayish-brown, body fuscous; forewing maculate with paler brown flecks. Male abdomen with posterior margin of seventh sternum bulging and produced, but not into a free process.

Male Genitalia: Ninth segment with a narrow, rounded ventromesal lobe from anterior margin. Cerci short; in dorsal aspect broadly divergent, almost triangular. Tenth tergum very short, in dorsal aspect with a small mesal excision. Clasper with basal region small, in lateral aspect tapering to a sharp point; in posteroventral aspect with inner margin sharply angled, tip shallowly bifid, with a sharp lateral point.

LARVA.—Length to 9 mm. Sclerites brown, muscle scars of head and thoracic nota distinctly paler; legs brown, femora darker along dorsal margins. Coxae of mid- and hindlegs with two rows of cuticular processes; femora of mid- and hindlegs with two enlarged setae on ventral margin; ventral fringe consisting of evenly spaced larger setae separated by fanlike arrays of shorter setae. A single pair of large submesal setae on first abdominal sternum; remaining setae of first and second sterna much smaller. Lateral fringe continuous from anterior of third segment to posterior of sixth segment. Gills, when present (often missing), arising in small stellate clusters from along posterior margins of abdominal terga.

TYPE MATERIAL.—Holotype, female, MCZ, S. nigrosoma Banks, “Type,” “Ithaca, N.Y.,” “Collection N. Banks,” “Type 11683,” “Sphinctogaster nigrisoma Bks. Type.” Pinned, abdomen cleared, studied.

Holotype, male, MCZ, B. notabulus Milne, “Glencarlyn, Va. 25 April,” “Collection N. Banks,” “22274 M.C.Z. Holotype Brachycent. notabulus Milne ,” “A25V35 Slide.” Pinned, abdomen cleared, studied.

Holotype, male, ANSP, B. adelus Ross, published as: “Ralph Stover Park, Bucks County, Pennsylvania; May 1, 1937; (J.W.H. Rhen [sic]).” Holotype not seen; two topotypic paratypes (INHS) studied.

MATERIAL EXAMINED.—USA, GEORGIA, Mud Creek, north Dillard, 10 Sep 1958, Flint and Wiggins, 7 larvae, 1 pupal case with sclerites. Dalton, 1 Apr 1949, W.E. Ricker 1 (INHS). Small creek at Jct. 53 and 183, near Dawsonville, 1 Apr 1949, W.E. Ricker, 1 (INHS). Cherokee Co., Etowah River, 5.5 mi. SE Ball Ground, 12 Apr 1971, Wallace and Woodall, 1 (INHS). Richmond Co., Little McBean Creek, Rt. 56, 17 Feb 1976, R.J. McKay, 10 larvae (ROM); same, but 20 Mar 1970 emerged from pupa collected 11 Mar 1970, Wallace & Sherberger, 1 (UGA). Stephens Co., Panther Creek, 2 mi. from junction with Tugallo River, 15 Apr 1969, J.B. Wallace, 12 (UGA).

MAINE, Penobscot Co., Penobscot River, Winn, 18 Oct 1979, T.M. Mingo, larvae (UMO, USNM).

MARYLAND, Plummer's Island, 28 Apr 1905, 9. Cecil Co., Octararo Creek, Rt. 1, 20 Jun 1981, W.L. Butler, 8 larvae (MWQMD).

NEW YORK, Ithaca, 1 (holotype B. nigrosoma, MCZ).

NORTH CAROLINA, Nantahala National Forest, Cullasaja River, near Highlands, 3300 ft., 27 Jun 1957, J.F. Hanson, 1 larva.

PENNSYLVANIA, Bucks Co., Ralph Stover Park, 1 May 1937, J.W.H. Rehn, 2 (paratypes, B. adelus, INHS).

SOUTH CAROLINA, High Falls, 16 Oct 1965, L. McCaskill, 1 larva (CUC). Seneca, 18 Sep 1965, A. Kallandelen, 1 larvae (CUC). Aiken Co., Boggy Gut Creek, 12 Feb 1977, Herlong and Prichard, 6 prepupae (CUC). Aiken Co., Hollow Creek at US 278, 4 Sep 1977, S.M. Prichard, 1 larva (CUC). Aiken Co., Upper Three Runs Creek, Savannah River Plant, 11 Mar 1977, Herlong and Prichard, 20, 20 (CUC); same, but Tinker Creek, 11 Mar 1977, 18, 1 (CUC); same, but Jun 1977, 30 larvae (CUC); same, but 19 Sep 1976, 4 larvae (CUC); same, but 16 Oct 1976, 36 larvae (CUC). Barnwell Co., Upper Three Runs Creek, Savannah River Plant, 28 Apr 1979, McEwan and Powell, 1 larva (CUC); same, but 1 Sep 1979, 1 larva (CUC); same, but Lower Three Runs Creek, 34 collections at about weekly intervals between 28 Apr 1979 and 16 Feb 1980, McEwan and Kelley, many hundreds of larvae, prepupae and pupae (CUC); same, but Mill Creek, 12 Feb 1977, Herlong and Prichard, 1 larva (CUC); same, but 26 Feb 1977, 3 prepupae (CUC). Oconee Co., Little River, old Hwy. 11 bridge, Salem, 3 Sep 1975, S.J. Nichols, 1 larva (CUC). Oconee Co., South Toxaway Creek, at S-37-90, 4 Apr 1976, J.W. Chapin, 2, 1 (CUC). Oconee Co., Ramsey Creek, US 76, 15 Jan 1976, Chapin and Menking, 2 larvae (CUC).

TENNESSEE, Blount Co., Little Tennessee River, Rt. 129, S Maryville, 13 Aug 1977, S.M. Prichard, 1 larva (CUC). Meigs Co., Big Sewee Creek, Tn. 58, 15 Sep 1982, D.A. Etnier, 69 larvae (UTK).

VIRGINIA, Glencarlyn, 25 Apr, 1, 4 (holotype, allotype and paratypes B. notabulus, MCZ). Great Falls, 20 Apr, 5 (MCZ). Craig Co., John's Creek, W.C. Snodgrass's land, 30 Apr 1977, T. Grimes, 18, 27 (VPI). Fauquier Co., Broad Run, Thorofare Gap, 3 Mar 1963, O.S. Flint, Jr., 6 larvae; same, but 26 Mar 1963, 50 prepupae; same, but 27 Mar 1962, 50 prepupae; same, but 16 Apr 1967, 10 empty pupal cases, 5 same, but 17 Apr 1963, 100s ; same, but 19 Apr 1962, Flint and Spangler, 2 metamorphotypes, 50 pupae; same, but 22 Jul 1961, O.S. Flint, Jr., 6 larvae. Hanover Co., South Anna River, Rt. 657, 21 Mar 1978, J.R. Voshell, Jr., 5 pupal cases with sclerites (VPI); same, but emerged in lab 7 Apr 1978, 5, 1, 1 pupa, cases (VPI). Spotsylvania Co., Pigeon Run, W Rt. 208 at Jct. with North Anna River, 13 Apr 1969, G.M. Simmons, Jr., 14, 2 (VPI); same, but 18 Apr 1970, 40, 2 (VPI).

WEST VIRGINIA, Cacapon River, Capon Bridge, 1 May 1944, Frison and Ross, 7 (paratypes B. adelus, INHS).

Oligoplectrodes Martynov, 1909:294.

ADULT.—Spurs 2, 2, 3 or commonly 2, 3, 3, or rarely 2, 2, 2.

Male Genitalia: Ninth segment in lateral aspect with sternum distinctly and broadly produced anteriad. Cerci elongate, in dorsal aspect fused on midline. Tenth tergum elongate, deeply divided mesally. Claspers elongate, inner margin slightly curved, with a large mesal lobe subapically.

LARVA.—Head and thoracic sclerites brown, essentially unmarked. Head with a distinct carina from anterior margin on genal halves, passing mesad to eye before ending. Mid- and hindfemora with a large seta on ventral margin, another on inner surface near apex, and a third on outer surface near base, dorsal margin with apical and subbasal setae distinctly enlarged; setae of filtering fringe virtually uniform in structure and length. A single pair of large, submesal setae on first abdominal sternum, lateral pair small and inconspicuous. Gills single.

TYPE-SPECIES.—Oligoplectrodes potanani Martynov (first included species