Polycentropus pixi Ross, 1944

Orfinger, Alexander Benjamin, 2023, Taxonomic revision of the Polycentropus confusus species group (Trichoptera: Polycentropodidae), Journal of Natural History 57 (41 - 44), pp. 1825-1916 : 1885-1889

Polycentropus pixi Ross

( Figures 30–31 , 51 )

Polycentropus pixi Ross, 1944: 66–67 , fig. 247, J; fig. 255, ♀; type locality ′ North Woodstock , New Hampshire ̍ ( INHS) .

Polycentropus pixi Nimmo, 1986: 198–199 , figs. 122–126, J.

Polycentropus pixi Armitage and Hamilton, 1990 : figs. A–D, J; figs. E–F, ♀.

Diagnosis. Males of P. pixi can be distinguished from those of all remaining species in the P. confusus species group by the dorsomesal margin of the ventral portion of each inferior appendage being produced into small sharp tooth near mid-length, visible in lateral view. Males of P. pixi are most similar to P. centralis in the shape and size of the phallus and the shape of the ventral portions of the inferior appendages in ventral view, and to P. carolinensis in the shape of the basodorsal process of each inferior appendage. From males of P. centralis , those of P. pixi can be further distinguished by the ventral curvature of the apical section of the phallus and the smaller, rounder head of the basodorsal process of each inferior appendage with a less pronounced and more blunt ventral projection. From males of P. carolinensis , those of P. pixi are further distinguished by the ventral portions of each inferior appendages being shorter and digitiform as seen in ventral aspect, and by the broader, straighter phallus.

Females of P. pixi can be distinguished from those of all remaining species of the P. confusus species group by the following combination of characters: the distinct shape of the smooth internal parts of gonopods VIII that is somewhat similar to the females of only P. stephani , the anterior parts of the genital chamber being broad and semi-circular with a slightly sinuous posterior margin, and the ventral plates being semi-elliptical and convergent.

Adult description

General. Length. of male 6.5–7.6 mm (mean = 6.9 mm; n = 4). Length of female 7.1– 8.0 mm (mean = 7.5; n = 3).

Male genitalia ( Figure 30A–E ). Abdominal segment VIII annular. Terga IX and X fused, membranous, extended caudad over bases of intermediate appendages. Sternum IX ovoid in lateral view, posterior margin sinuous. Intermediate appendages originating beneath terga IX+X and extending caudad beyond them, their apices each bearing 4 small setae; in dorsal view apices proximate, subparallel. Bodies of pre-anal appendages each broad, produced caudad, extended furthest caudad at mid-height, ventral half of posterior margin sinuous; dorsal process long, curved posteroventrad, extending roughly even with ventral margin of head of basodorsal process of corresponding inferior appendage, acute apically; in dorsal view slender, elongate, gradually convergent. Inferior appendages in lateral view each with capitate basodorsal process erect with wide, moderately long neck and small head round dorsally and projecting ventrad with its blunt apex visible above main body of appendage, main body of appendage wide basally, dorsomesal margin produced into small sharp tooth near mid-length, surface with shallow dorsomesal excavation along middle 1/3 length, tapering to blunt slightly upturned apex anterior to intermediate appendages; in ventral view basally subparallel to about mid-length, slightly divergent beyond mid-length, digitiform, slender, distally tapering to round apex, lateral margin slightly concave near mid-length, basodorsal process oblong, mostly hidden by main body of inferior appendage, in cleared specimen broad, with medial round projection exposed beyond inner margin of main body of inferior appendage, meeting or nearly meeting medial projection of basodorsal process of other inferior appendage; in caudal view oblong, with medial projection round. Phallus a fully sclerotised tube, in lateral view with larger base, nearly straight along 4/5 length, apical section subrectangular, curved ventrad roughly 25°, internal spinules absent, internal phallic sclerite moderate length, semi-vertical, with slender, acute anterodorsal base and widening to subrectangular posteroventral apex.

Female genitalia ( Figure 31A–B ). Venter VIII in ventral view with ventral plates convergent, narrow, semi-elliptical, tapering apically, covered with setae; in lateral view each terminating in round posterior apex; posterior apex of external parts of gonopods VIII in ventral view with posterior margin broadly round; in lateral view extending dorsoposterad beyond ventral plates, tapering to round apex; internal parts of gonopods VIII in ventral view visible through venter VIII even in uncleared specimen, appearing smooth, darker than surrounding tissue, subparallel for most of length, with round anterior bases slightly divergent, round posterior apices slightly anterior of apices of ventral plates with sharp caudolateral corner meeting ventral plates, anterior ends tapered, extending to sclerotised external part of gonopods VIII near base of ventral plates, surfaces bearing lateromesal excavation along 4/5 length; in ventral view anterior part of genital chamber sclerotised, broad, semi-circular, posterior margin slightly sinuous, wrapping around posterior apex of processus spermathecae; processus spermathecae circular with distomesal elevation bearing opening of ductus spermathecae.

Larva. Unknown.

Pupa. Unknown.

Notes. One male specimen of P. pixi listed as having been collected in Nova Scotia and a second listed as having been collected in New Jersey are included in the NMNH database but could not be found and are lacking accession codes. Nova Scotia and New Jersey would represent new province and state records, respectively, for the species, but without the specimens and with little collection data, these cannot be confirmed.

Biology. Almost nothing is known of the biology of this uncommon species. Adults have been collected from May to July near cool lotic systems ranging from low-order streams to navigable rivers.

Distribution ( Figure 51 ). Canada *: New Brunswick *; USA: Massachusetts, New Hampshire, New York, Ohio, Pennsylvania, Vermont, Virginia.

This species appears to be restricted to the north-eastern United States and far eastern Canada . The two male specimens reported here from New Brunswick, Canada, represent new province and country records . Several states and provinces from which P. pixi has not been reported despite neighbouring territories having confirmed records of the species include West Virginia , Maryland , Delaware , New Jersey , Connecticut , Rhode Island, Maine, Quebec, Prince Edward Island, and Nova Scotia.

Material examined. Holotype: USA. New Hampshire: Grafton County, North Woodstock , At Light, Frison and Ross coll., 21-vi-1941, 1 male ( INHS Insect Collection 38,130) . Paratypes: USA. New Hampshire: Grafton County, North Woodstock , At Light, Frison and Ross coll., 21-vi-1941, 1 female ( INHS Trichoptera 24,585) . New York: Wyoming County, Varysburg , 18-vi-1941, 1 female ( INHS Trichoptera 24,586) .

Non-type material. Canada. New Brunswick: Northumberland County, Renous River, McGraw Brook , [N46°49 ʹ 21.00″, W66°06 ʹ 33.12″], X. Zhou and D. Baird coll., 23-vi-2008, 1 male (08NBEPT-0050) new country record, 1 male (08NBEPT-0138 ) new country record. USA. New York: Greene County, Winter Clove BLT, Maple Lawn Road , [N42°15 ʹ 25.56″, W74° 02 ʹ 24.36″], L. Myers and B.C. Kondratieff coll., 24-vi-2007, 1 male ( BYU) . Virginia: Bath County, Blowing Springs, Route 39, 10 miles west of Warm Springs ; Back Creek , [N38° 04 ʹ 12.00″, W79°53 ʹ 17.88″], O. Flint coll., 17-v-2004, 1 male (USNMENT01507896) , 1 male (USNMENT01507895) , 1 male (USNMENT01507894) , 1 male (USNMENT01507893) . Highland County, Route 84, Townsend Draft , [N38°17 ʹ 59.64″, W79°46 ʹ 22.80″], O. Flint and S.Roble coll., 8-vi-2011, 1 female (USNMENT01507903) , 1 female (USNMENT0157904) , 1 female (USNMENT01507902), 1 female (USNMENT01507901), 1 female (USNMENT01507900), 1 female (USNMENT01507899), 1 female (USNMENT0157905), 1 male (USNMENT01507898), 1 male (USNMENT01507897) . Rockingham County, Hone Quarry Camp , [N38°27 ʹ 43.92″, W79°08 ʹ 06.00″], R.A Flint and O. Flint coll., 17–18-vii-1964, 1 female (USNMENT01507892), 1 male (USNMENT01507891).

Figures

Figure 30. Polycentropus pixi Ross, 1944, male genitalia (holotype). A. left lateral (with phallus removed); B. dorsal; C. segment IX and inferior appendages, ventral; D. phallus, left lateral; E. dorsobasal process of right inferior appendage, caudal.

Figure 31. Polycentropus pixi Ross, 1944, female genitalia. A. left lateral; B. ventral.

Figure 51. Known Canadian province and US state distribution of Polycentropus pixi Ross, 1944, as indicated by grey shading.