Polycentropus elarus 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 : 1866-1870

Polycentropus elarus Ross

( Figures 21–22 , 46 )

Polycentropus elarus Ross, 1944: 666 , fig. 245, J; fig. 256, ♀; type locality ′ Costello Lake, Algonquin Park , Ontario ̍ ( INHS, lost) .

Polycentropus elarus Nimmo, 1986: 197 , figs. 140–144, J; figs. 145–146, ♀.

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

Diagnosis. Males of Polycentropus elarus are most similar to those of P. aileenae and P. stephani in the ventral aspect of the ventral portions of the inferior appendages and to P. aileenae also in the size and shape of the head of the basodorsal processes of the inferior appendages. From these and other males of species in the group, P. elarus can be distinguished by the dorsal processes of each pre-anal appendage being directed caudad and slightly curved dorsad and convergent apically. From males of P. aileenae , those of P. elarus are distinguished by the shorter basodorsal processes and ventral portions of the inferior appendages and by the subparallel rather than divergent ventral portions of the inferior appendages. From males of P. stephani , males of P. elarus are identified by the capitate head of the basodorsal process of the inferior appendage and by the lack of a basoventral spur on the phallus. From all other species, males of P. elarus are distinguished by the size and shape of the small, round heads of the basodorsal processes of the inferior appendages and by the shape of the ventral portions of the inferior appendages as seen in ventral view.

Females of P. elarus are distinguished from female of all other members of the Polycentropus confusus species group by the combination of the posterior apex of external parts of gonopods VIII in lateral view being slender, almost digitiform, and either oriented caudad or recurved dorsad and the anterior part of the genital chamber sclerotised, being U-shaped and appearing connected to the smooth internal parts of gonopods VIII that are curved about 90° laterad to apices of ventral plates distally.

Adult description

General. Length. of male 6.0– 8.5 mm (mean = 7.2 mm; n = 6). Length of female 8.6– 9.5 mm (mean = 9.0 mm; n = 5).

Male genitalia ( Figure 21A–E ). Abdominal segment VIII annular. Terga IX and X fused, membranous, extended caudad over bases of intermediate appendages. Sternum IX subovoid in lateral view. Intermediate appendages originating beneath terga IX+X and extending beyond them, oriented caudad, their apices each bearing 4 small setae; in dorsal view apices proximate, subparallel to divergent. Bodies of pre-anal appendages each with small, round subtriangular posteroventral process with subtle ventral emargination; dorsal processes long, each curved ventrad for 2/3 length, curved slightly dorsad for final 1/3 length, extending only to dorsal portion of body of pre-anal appendage, acute apically; in dorsal view stocky, elongate, subparallel for nearly entire length, convergent apically. Inferior appendages in lateral view each with capitate basodorsal process erect with moderately long neck and small head round dorsally and projecting ventrad with its round, subtriangular apex visible above main body of appendage, main body of appendage with broad base, dorsal and ventral margins tapering evenly to round apex extended posterad slightly beyond intermediate appendages; in ventral view subparallel, wide basally, margins subparallel for ½ length, inner margin curved abruptly outward beyond ½ length to narrow round apex, basodorsal process completely hidden by main body of inferior appendage, in cleared specimen small, with medial round projection; in caudal view oblong, with medial projection round. Phallus a fully sclerotised tube, in lateral view with larger base, curved about 20° ventrad slightly beyond mid-length, apical section slightly enlarged, subrectangular, posterior margin slightly sinuous with ventral lip, with internal spinules absent, internal phallic sclerite long, horizontal, with round slender, acute anterior base and wide subrectangular posterior apex.

Female genitalia ( Figure 22A–B ). Venter VIII in ventral view with ventral plates convergent, narrow, semi-elliptical, tapering apically, covered with setae; in lateral view each narrow at base, wide at mid-length, ventral margin sinuous beyond mid-length, narrowing to round posterior apex; posterior apex of external parts of gonopods VIII in ventral view with posterior margin subtriangular and round mesally; in lateral view extending beyond ventral plates in flat process with its tiny apex projected caudad to recurved dorsad; internal parts of gonopods VIII in ventral view visible through venter VIII even in uncleared specimen, appearing smooth, darker than surrounding tissue, subparallel basally for 4/5 length, curved about 90° laterad to apices of ventral plates distally, sinuous along length, tapering gradually to apex, anterior ends appearing connected to anterior part of genital chamber at sclerotised external part of gonopods VIII at basal third of ventral plates; in ventral view anterior part of genital chamber sclerotised, U-shaped, strongly sinuous, wrapping around posterior apex of processus spermathecae; processus spermathecae large, subovoid with central elevation bearing opening of ductus spermathecae.

Larva. Described by Orfinger et al. (2023).

Pupa. Unknown.

Notes. The holotype is listed by Ross (1944) as deposited at INHS but could not be located and is presumed lost. INHS Insect Collection 37255 specimen designated as neotype.

Biology. Adults of this fairly common species is found near cool, clear, flowing streams of with various substrates depending on locality. Adults have been collected from April to September, sometimes in abundance. The single known late-instar larva was collected in June from an unimpaired ( Bott et al. 2012), small, cool, fast-flowing stream with rocky substrate.

Distribution ( Figure 46 ). Canada: Ontario, Quebec; USA: Alabama, Florida, Georgia, Illinois *, Indiana, Kentucky, Massachusetts, New Hampshire, New York, North Carolina , Ohio, Pennsylvania, Tennessee, Virginia, West Virginia.

This species is widespread in the eastern United States and Canada. It is likely that this species will be encountered in additional states and provinces neighbouring areas from which it has been taken. For example, Orfinger and Moulton (2021) recently reported the species from the Florida panhandle based on a single male specimen, and is reported herein for the first time from Illinois based on five male specimens. Similarly, it would be unsurprising if P. elarus was eventually recorded from Mississippi, Michigan, South Carolina , Maryland, New Jersey, Vermont , Maine , Delaware , Connecticut , Rhode Island , and New Brunswick.

Material examined. Neotype: Canada. Ontario: Algonquin Park, Ontario Fish Research Lab , Costello Lake , Cage No. 1, W.M. Sprules coll., 11-vi-1939, 1 male ( INHS Insect Collection 37,255) . Paratype: USA. New York: Adirondack Park, Bear Brook near Blue Mountain Lake , Frison and Ross coll., 19-vi-1941, 1 male ( INHS Trichoptera 24,573) . Allotype: Canada. Ontario: Algonquin Park, Ontario Fish Research Lab , Costello Lake , Cage No. 1, W.M. Sprules coll., 22-vi-1939, 1 female ( INHS Insect Collection 37,262) . Non-type material: Canada. Ontario: Algonquin Provincial Park, Costello Lake , Ontario Fisheries Research Laboratory, W.M. Sprules coll., 22-vi-1939, 1 female (recorded by Ross as male) ( INHS Trichoptera 54,986) . USA. Alabama: Dekalb County, Fort Payne, Straight Creek , UV light trap, 468 masl, [N34°38 ʹ 34.98″, W85°36 ʹ 41.52″], A. Orfinger and A. Perilla coll., 27–28-vi-2020, 116 males ( FAMU) . Florida: Washington County, Econfina Creek Water Management Area, Unnamed ravine stream (lower reach) that flows into Whitewater Lake off Porter Pond Rd., [N30°28 ʹ 46″ W85°33 ʹ 14″], Rasmussen et al. coll., 6-vi-2009, 1 male ( FAMU) . Illinois: Ford County, Paxton Railroad Prairie , light, 229 masl, [N40°25 ʹ 08.33″, W88°06 ʹ 51.70″], J.D. Unzicker coll., 7-vi-1962, 3 males ( INHS Insect Collection 38,151) new state record. Pope County, Simmons Creek, War Bluff Valley Audobon Society Sanctuary , 8.7 km N Golconda, black light trap, [N37°26 ʹ 43.84″, W88° 29 ʹ 19.64″], J.L. Robinson coll., 29-viii-2015, 2 males ( INHS Insect Collection 797,581) new state record. Indiana: Montgomery County, Shades SP , Crystal Falls Stream , L. Chandler and R. Smith coll., 12-v-1963, 1 female ( INHS Trichoptera 54,984) . Kentucky: Bell County, Martins Fork, Cumberland River downstream of upper bog, 735 masl, M. Geraghty and C. Parker coll., 19-vii-2006, 1 female ( CUGA 4851 ) . Pennsylvania: Schuylkill County, Rattling Run , [N40°35 ʹ 02.40″, W76°01 ʹ 01.20″], T. Bringloe, V. Harvey, S. Ripley, K. Rondollo coll., 13-vi-2013, 1 larva ( BIOUG07980 - B 07) . Tennessee: Greene County, Tusculum College , [N36°10 ʹ 26.00″, W82°45 ʹ 39.99″], M. Wright coll., 23–30-v-1946, 1 male, 1 female ( INHS Trichoptera 54,983) . Virginia: George Washington National Forest , Passage Creek , G. Washington Nat. For., For. Rt. 274, 396 masl, [38°43 ʹ 30″, W78°32 ʹ 24″], Blahnik and Contreras coll., 19-ix-1992, 1 male ( UMSP 000048997 ) . West Virginia: Hardy County, 3 miles north-east of Mathias, [N38°33 ʹ 00.00″, W78°29 ʹ 24.00″], D. Smith coll., 27-vi -2007, 1 male ( BYU) .

Figures

Figure 21. Polycentropus elarus Ross, 1944, male genitalia (neotype). 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 22. Polycentropus elarus Ross, 1944, female genitalia. A, left lateral. B, ventral.

Figure 46. Known Canadian province and US state distribution of Polycentropus elarus Ross, 1944, as indicated by grey shading.