Pagastia (P.) orthogonia Oliver, 1959

Makarchenko, Eugenyi A., 2019, Review of the genus Pagastia Oliver (Diptera: Chironomidae: Diamesinae) from North America, with description of P. (P.) subletteorum sp. nov., Zootaxa 4664 (1), pp. 115-128 : 118-121

Pagastia (P.) orthogonia Oliver

( Figs. 7–13 , 21 , 26–32 )

Pagastia orthogonia Oliver, 1959: 51 ; Makarchenko & Makarchenko 2000: 174; Endo 2004: 283; Caldwell 2007: 70; Ashe & O’Connor 2009: 296; Namayandeh & Culp 2016: 206; Namayandeh et al. 2016: 58.

Pagastia sp. A Oliver, Roussel 1982: 854.

Material. Holotype: 1 adult male, U.S.A.: Alaska, 163º W, Cold Bay , on tundra, 18.VIII.1952, leg. W.R. Mason, CNC no. 19627 . Paratype: 1 adult male, U.S.A., Michigan, Epoufette , 15.V.1955, leg. J.R. Vockeroth . 1 adult male (reared), exuviae of pupa and larval skin, U.S.A., Wisconsin, 11 miles East, 4 miles South of Siren, Burnett County, cold stream ( Spring Brook ), 22.I.–28.II.1967, leg. D. Hansen, slide DH 69-182 ; 2 adult males, same location, light trap, 1–2.V.1968, leg. D. Hansen ; 2 adult males, same location, 21.IX.1968, leg. D. Hansen ; 7 larvae, same location, Spring Brook , drift trap, 7–8.IX.2014, leg. D. Hansen ; 13 larvae, same location, Spring Brook , 24.I.2016, leg. D. Hansen . 1 adult male, 16 pupal exuviae, U.S.A.: South Dakota, Lawrence County, 3 miles West, 10 miles South of Spearfish, Spearfish Creek , alt. 1585 m, 29.IX.1968, leg. D. Hansen . 7 pupal exuviae, U.S.A., Minnesota, Washington County, first order, summer-cool stream, Valley Creek , drift trap, 9–10.V.2015, leg. D. Hansen.

Adult male (n = 5).

Total length 3.8–5.3 mm. Total length/wing length 1.42–1.57.

Coloration. Head, thorax, legs, and abdomen brown to dark brown; antennae light brown or yellowish-brown; wings greyish.

Head. Eyes bare and extended dorsomedially. Temporal setae consisting of 4 coronals, 1–3 orbitals, 8–13 verticals, and 6–12 postorbitals. Clypeus with 11–21 setae. Antenna with 13 flagellomeres and a well developed plume; pedicel with 2 setae 52–60 μm long; terminal flagellomere with 1 subapical setae 20–60 μm long. AR 1.58–1.95. Palpomere lengths (in μm): 40–48; 80–92; 156–196; 148–188; 168–200. Distal part of palpomere 3 with sensilla capitata of 8–12 μm diameter. Palpomeres 1–5 length/head width 0.99–1.04.

Thorax. Antepronotum with 4–5 dorsomedial setae and 5–7 ventrolateral setae. Acrostichals 5–32 (40–68 μm long, in 1–2 rows), dorsocentrals 10–19 (in 1–2 rows), prealars 7–15, scutellars 11–29 (in 2–3 rows).

Wing. Length 2.48–3.60 mm; width 0.72–0.96 mm. Membrane usually without setae, very rarely with several setae near the tip of the wing. R with 16–24 setae, R 1 with 6–14 setae; R 4+5 with 12–18 setae; other veins without setae. Costa extension 57–115 μm long. RM length/MCu length 2.0–2.2. Anal lobe developed, rounded and slightly protrude. Squama with 42–46 setae in 2–3 rows. Alula without setae. VR 0.90.

Legs. Spur of fore tibia 48–100 μm long; spurs of mid tibia 52–76 μm and 60–80 μm long; spurs of hind tibia 64–80 μm and 72–92 μm long. Hind tibial comb with 10–13 setae. Lengths and proportions of leg segments as in Table 2.

Hypopygium ( Figs. 7–13 , 21 ). Tergite IX with 16–26 setae on each side and with an anal point 70–100 μm long, parallel-sided, with rounded apex and sometimes with a pore in apical part ( Fig. 12 ). Laterosternite IX with 7–14 setae. Transverse sternapodeme narrow, arcuate or trapezoidal, 204–252 μm long. Phallapodeme 116–148 μm long. Median aedeagal lobe absent; lateral aedeagal lobe 120–140 μm long. Gonocoxite 260–328 μm long. Gonostylus 168–188 μm long, with megaseta 12–20 μm long. HR 1.50–1.74.

Pupa (n=5). Total length 4.8–5.4 mm. Exuviae range from yellow to grayish to light brown.

Cephalothorax. Frontal apotome with 2 setae 252–260 µm long. Thorax granulated, with 4 dorsocentral setae; anterior Dc 1 and Dc 2 36–40 µm long, Dc 3 12 µm long, Dc 4 44 µm long. Distance between Dc 1 and Dc 2 76 µm; between Dc 2 and Dc 3 72 µm; between Dc 3 and Dc 4 300 µm. Antepronotum with 2 median setae 120–232 µm long and 1 lateral seta 156–168 µm long. Precorneal setae lengths (μm): Pc 1 120–160, Pc 2 168–220, Pc 3 160–188. Bases of the three precorneals form a triangle.

Abdomen. Tergite I without shagreen or with only very fine shagreen of pale spinules along posterior edge. Tergite II with easily visible fine shagreen in anterior ¼ and more extensive shagreen of larger spinules along posterior edge; middle part of tergite with very small and sparsely located spinules. Tergites III–VIII fully covered with shagreen of spinules which become larger near the posterior edge ( Fig. 26 ). Spinules of the shagreen of tergites III–VII along posterior edge are directed anteriorly, and these spinules arise from dark spots ( Figs. 27–28 ). Tergite IX with fine shagreen only anteriorly. Tergites I–VIII with 5 D setae, of which D 3 seta is the longest (116–148 μm) and is split into 2–3 branches; very rarely the D 3 seta can be simple ( Fig. 30 ). Sternites without shagreen. Segment I with 3 pairs of lateral setae, with L 1 simple, L 3 divided into 2 branches, and L 4 divided into 4–5 branches. Segments II–VIII with 4 pairs of lateral setae, most of which are divided into several branches ( Figs. 31–32 ). Lateral setae of segment VII are located in posterior half ( Fig. 27 ), lateral setae of segment VIII are located in posterior 1/3. More characteristics on abdominal lateral seta are provided in Table 3 . Anal lobe 402–426 µm long, with triangular apical tubercle in apical part, and with 3 hair-like anal macrosetae 312–992 µm long and 1–2 simple median setae 64–76 µm long ( Fig. 29 ). Male genital sac not or only slightly extending beyond anal lobe.

Larva was described by Oliver & Roussel (1982), Namayandeh & Culp (2016) and Namayandeh et al. (2016).

Remarks. P. orthogonia is closely related to the Palaearctic species P. (P.) lanceolata (Tokunaga) . Males can be distinguished only by features given in the key below. Pupae and larvae of these two species cannot as yet be distinguished.

Distribution. Japan: Hokkaido; Russian Far East: Amur River basin (lower part); Canada: Nunavut, Prince Edward Island; U.S.A.: Alaska, Georgia, Michigan, Minnesota, North Carolina, North and South Dakota, Ohio, Tennessee, Wisconsin.

Figures

FIGURES 7–13. Pagastia (P.) orthogonia Oliver, males from Alaska (holotype) (7–9) and South Dakota (10–13). 7, 10, hypopygium in dorsal view; 8, gonocoxite and gonostylus in ventral view; 9, inner structures of hypopygium; 11, gonostylus; 12, anal point; 13, gonocoxite and gonostylus in dorsal view. Scale bars: 50 µm.

FIGURES 21–25. Pagastia (P.) orthogonia Oliver from South Dakota (21) and P. (P.) partica (Roback) (22–25), males. 21, 23, 25, hypopygium in dorsal view; 22, part of hypopygium without tergite IX; 24, anal point.

FIGURES 26–40. Pagastia (P.) orthogonia Oliver (26–32) and P. (P.) partica (Roback) (33–40), pupae. 26, 33, tergite IV; 27, tergite VII; 28, spinules of posterior shagreen of tergite IV; 29, 40, male genital sacs and apex of anal lobes with median setae; 30, D3 seta of tergite IV; 31, L2 seta of segment VII; 32, L3–L4 setae of segment VIII; 34, Dc1 setae of thorax; 35, Dc3 seta of thorax; 36, tergite VIII; 37, L1 seta of segment VIII; 38, L4 seta of segment IV; 39, L2 seta of segment VIII. Ms, median setae of anal lobes.