Pagastia (P.) donoliveri Makarchenko et Hansen, 2020

Makarchenko, Eugenyi A. & Hansen, Dean C., 2020, Pagastia (P.) donoliveri sp. nov. - a new Nearctic alpine stream chironomid species (Diptera: Chironomidae: Diamesinae) from the Beartooth Mountains, Wyoming U. S. A., Zootaxa 4755 (1), pp. 171-176 : 171-175

Pagastia (P.) donoliveri Makarchenko et Hansen , sp. nov.

( Figs. 1–9 )

urn:lsid:zoobank.org:act:9E21409F-D361-41D5-B5A6-FF0857DC8C56

Material. Holotype: adult male, U.S.A.: Wyoming, Park County, Beartooth Pass region, Malaise trap over small stream feeding Frozen Lake , alt. 3127 m above sea level, N 44°57’42.12”, W 109°29’08.12”, 30–31.VIII.2017, leg. Dean C. Hansen. Paratype: 1 adult male, same data as holotype .

Derivatio nominis. The species is named in honour of the Canadian chironomid taxonomist Donald Raymond Oliver.

Adult male (n = 2).

Total length ca 5.4–5.6 mm.

Coloration (specimens in Euparal). Head, thorax, legs, and abdomen brown to dark brown; antennae light brown; wings greyish.

Head. Eyes bare and strongly extended dorsomedially ( Fig.1 ). Temporal setae 33–52, including 4 coronals, 8– 14 preoculars, 14–22 verticals, and 7–11 postorbitals. Clypeus with 23–24 setae. Antenna with 13 flagellomeres and developed plume, these setae 328–590 μm long; pedicel with 3 setae 56–64 μm long; terminal flagellomere with 1 subapical setae 50–52 μm long; flagellomeres lengths (in μm): 72–76; 28; 24–28; 32; 36–40; 36–40; 40–44; 40–42; 42–44; 44; 44–52; 44–48; 592–636; AR 1.22–1.26. Palpomere lengths (in μm): 60–68; 96–100; 192–196; 168–208; 260. Palpomere 3 distally with sensilla capitata (diameter 12 μm). Palpomeres 1–5 length/head width 0.95–1.24.

Thorax. Antepronotum with 6–7 dorsal and 13–18 lateral setae. Acrostichals 19–26 (60–92 μm long), dorso- centrals 41–43 (in 1–2 rows in anterior 2/3 and in 3 rows in posterior 1/3), prealars 22–24, scutellars ca 55 ( Figs. 2–3 ).

Wing. Length 4.28–4.36 mm; width 1.16 mm. Membrane with setae 20–24 μm long on wing apex. R and R 1 with 59–64 setae in 1–2 rows; R 4+5 with 34–35 setae. Setae on R, R 1, R 4+5 40–52 μm long. Costa extension 49–66 μm long. RM length/MCu length 2.5–3.3. Anal lobe developed, outline rounded. Squama with 40–46 setae 48–152 μm long, in 1–2 rows. VR 0.84–0.93.

Legs. Spur of fore tibia 88–92 μm long; spurs of mid tibia 68–72 μm and 72–76 μm; of hind tibia 112–116 μm and 72 μm long. Hind tibial comb with 10 setae. Lengths and proportions of leg segments as in Table 1.

Hypopygium ( Figs. 4–9 ). Tergite IX with 20–25 setae on each side 64–120 μm long. Anal point almost parallelsided in dorsal view, 72–88 μm long, with narrow seta-like apical peg 28 μm long ( Fig. 8 ). Laterosternite IX with 7– 11 setae. Transverse sternapodeme narrow, anterior margin nearly straight. Phallapodeme with lateral aedeagal lobe only ( Fig. 5 ), these 172–196 μm long, elongate and tapering to thin rounded apex. Gonocoxite 320–328 μm long, with basal plate and lobe-like median field. Gonostylus 196–224 μm long, narrow and ribbed, with rounded basal lobe in outer side and with lobe-like “heel” apically; megaseta 16–20 μm long ( Figs. 4 , 6–7, 9 ). HR 1.46–1.63.

Pupa and larva unknown.

Diagnosis. The male of the new species is most closely related to the Japanese species P. (P.) hidakamontana Endo , but it may be clearly distinguished from later by the shape of the gonostylus and some other features, namely the gonostylus with a rounded basal lobe in its outer side and a lobe-like “heel” apically; anal point of tergite IX 72–88 μm long, with narrow seta-like apical peg 28 μm long ( Figs. 4 , 6, 7, 9 ); AR 1,22–1,26. Gonostylus of P. (P.) hidakamontana with small basal lobe in outer side, apically rounded, without “heel”; anal point 100–116 μm long and apical peg broad, 24–33 μm long ( Endo 2004, Figs. 1–6 ); AR 1.56–1.75. See also key below.

Figures

FIGURES 1–3. Pagastia (P.) donoliveri sp. nov., male. 1, head in frontal view; 2, pronotum and mesonotum in dorsal view; 3, part of thorax in lateral view.

FIGURES 4–5. Pagastia (P.) donoliveri sp. nov., male. 4, hypopygium in dorsal view; 5, lateral aedeagal lobes. Scale bars: 50 µm.

FIGURES 6–9. Pagastia (P.) donoliveri sp. nov., male. 6–7, parts of hypopygium in dorsal view; 8, apex of anal point with peg; 9, gonostylus.