Pagastia (P.) partica (Roback), 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 : 121-123

Pagastia (P.) partica (Roback)

( Figs. 14–17 , 22–25 , 33–38 )

Syndiamesa partica Roback, 1957: 4 .

Pagastia partica (Roback) Oliver 1959: 52 ; Oliver & Roussel 1982: 853; Makarchenko & Makarchenko 2000: 174; Ashe & O’Connor 2009: 296.

Material. 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 ; 1 adult male, 1 pupa, 1 pupal exuviae, U.S.A., Washington, Yakima River , 26.III.1995, leg. V. Teslenko ; 14 larvae, U.S.A., Wyoming, Park County, Beartooth Pass region, small stream feeding Frozen Lake , alt. 3133 m, 11.IX.2002, leg. D. Hansen.

Adult male (n = 2).

Total length 5.6–6.1 mm. Total length/wing length 1.20–1.33.

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

Head. Eyes bare and extended dorsomedially. Temporal setae consisting of 4 coronals, 5 preoculars, 12–14 verticals, and 3–4 postorbitals. Clypeus with 23–40 setae. Antenna with 13 flagellomeres and a well developed plume; pedicel with 1 seta 32–40 μm long; terminal flagellomere with 1–2 subapical setae 36–56 μm long. AR 2.35–3.40. Palpomere lengths (in μm): 60; 129–152; 256–260; 220–276; 208–268. Distal part of palpomere 3 with sensilla capitata 12 μm in diameter. Palpomeres 1–5 length/head width 1.04–1.19.

Thorax.Antepronotum completely covered with 40–63 setae.Acrostichals 14–16 (40–54 μm long, in 1–2 rows), dorsocentrals 26–27 (in 1–2 rows), prealars 31, scutellars ~ 45.

Wing. Length 4.2–5.1 mm; width 1.04–1.2 mm. Membrane without setae. R and R 1 with 32–33 setae; R 4+5 with 16–18 setae; other veins without setae. Costa extension 115–123 μm long. RM length/MCu length 3.1–3.3. Anal lobe developed, protrudes forward. Squama with ~ 40 setae in 2 rows. Alula without setae. VR 0.89–0.91.

Legs. Spur of fore tibia 96–136 μm long; spurs of mid tibia 60–92 μm and 68–92 μm long; spurs of hind tibia 100–136 μm and 76–92 μm long. Hind tibial comb with 13–14 setae. Lengths and proportions of leg segments as in Table 4 .

Hypopygium ( Figs. 14–17 , 22–25 ). Tergite IX with 19–25 setae on each side and with an anal point 132–140 μm long apically with peg 36–38 μm long ( Fig. 24 ). Laterosternite IX with 9–11 setae. Transverse sternapodeme 336–340 μm long. Phallapodeme 152–172 μm long. Median aedeagal lobe 144–180 μm long, widest medially, then tapering abruptly and with the apex forming a sharp hook; lateral aedeagal lobe 168–188 μm long ( Figs. 16–17 ). Gonocoxite 340–400 μm long. Gonostylus 248–280 μm long, with megaseta 10–12 μm long. HR 1.35–1.43.

Pupa (n=5). Total length 6.0– 7.1 mm Exuviae yellowish-brown or light brown.

Cephalothorax. Frontal apotome with 2 setae 276–308 µm long. Thorax granulated, with 4 dorsocentral setae: Dc 1 20–44 µm long, divided into 3–7 branches ( Fig. 34 ); Dc 2 52–60 µm long, simple; Dc 3 20–28 µm long, divided into 2–3 branches ( Fig. 35 ); Dc 4 52–58 µm long, simple. Distance between Dc 1 and Dc 2 68–88 µm; between Dc 2 and Dc 3 56–88 µm; between Dc 3 and Dc 4 380–448 µm. Antepronotum with 2 median setae 304–356 µm long and 1 lateral seta 208–264 µm long. Precorneal setae lengths (μm): Pc 1 160–284, Pc 2 348–360, Pc 3 196–210. Bases of the three precorneals usually form a triangle but in some cases form a nearly straight line.

Abdomen. Tergite I with fine shagreen of spinules posteriorly. Tergites II–VI with shagreen of spinules in anterior, middle and posterior areas but without shagreen laterally ( Fig. 33 ). Tergites VII–VIII fully covered with shagreen of spinules but shagreen becomes finer in lateral areas ( Fig. 36 ). Tergite IX with fine shagreen only anteriorly. Spinules of shagreen of tergites III–VII along posterior edge are directed anteriorly and are stronger than those of remainder of tergites. Tergites I–VII with 5 D setae, with D 3 seta longest (120–192 μm) and in most cases simple, only occasionally divided into 2 branches. Sternites without shagreen. Segment I with 2 pairs of lateral setae, with L 1 simple and L 4 divided into 2–3 branches. Segments II–VIII with 4 pairs of lateral setae, these setae on more posterior segments are divided into two ( Fig. 38 ) to several branches ( Figs. 37, 39 ). Lateral setae of segment VII are located in posterior half, lateral setae of segment VIII are located in posterior 1/3 ( Fig. 36 ). More detailed characteristics on abdominal lateral seta are provided in Table 5 . Anal lobe 607–689 µm long, with triangular apical tubercle, with 3 hair-like anal macrosetae 410–492 µm long and 1 median setae 6–80 µm long, this divided into 3–4 branches ( Fig. 40 ). Male genital sac not or only slightly extending beyond anal lobe.

Larva in detail was described by Oliver & Roussel (1982).

Remarks. Pupae and larvae cannot be distinguished from P. nivis (Tokunaga) based on the present information.

Distribution. Canada (Yukon Territory), U.S.A. (Alaska, Utah, Wyoming, South Dakota, Washington).

Figures

FIGURES 14–18. Pagastia (P.) partica (Roback) (14–17) and P. (H.) sequax (Garrett) (lectotype) (18), males. 14, 18, hypopygium in dorsal view; 15, gonostylus; 16, aedeagal lobes; 17, part of hypopygium without tergite IX. MAl, median aedeagal lobe. 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.