Derotanypus limbatus (Lundström) Lundstrom, 2004

Saether, Ole A., 2004, The chironomids (Diptera, Chironomidae) described by Lundström (1915) from arctic Siberia, with a redescription of Derotanypus sibiricus (Kruglova & Chernovskii), Zootaxa 595, pp. 1-35 : 27-30

Derotanypus limbatus (Lundström) , comb. n.

(Figs. 24–26)

Ablabesmyia limbata Lundström, 1915: 24 .

Ablabesmyia quadrinotata Lundström, 1915: 25 , syn. n.

Type material. Lectotype ɗ, here designated: RUSSIA: New Siberian Islands, "Holzgebirge”, 24 vi 1902, A. A. Birula. Paralectotypes: RUSSIA: New Siberian Islands, west coast, beach of the river Bolschaja, and Kotelnyj Islands, 1 ɗ, 2 Ψ, 18 vi, 2 vii 1903 [24 (11) vi 1903 in Lundström]; M. I. Brussnew. Holotype ɗ of A. quadrinotata : RUSSIA: New Siberian Islands, north coast at a lake, 4 vii (21 vi) 1902, A. A. Birula.

MALE IMAGO (n = 1–3)

Total length 7.08–7.86 mm. Wing length 3.94–4.60 mm. Total length/wing length 1.71–1.80. Wing length/length of profemur 2.38. Coloration yellowish brown to brownish black with darker vittae. Legs uniformly dark brown or, in A. quadrinotata , pale brown. Wing with dark spot over both cross­veins.

Head. AR 2.71–2.88. Penultimate flagellomere 1210–1332 m long, ultimate flagellomere 123–132 m long. Temporal setae 58–65, including 14–18 inner verticals, 18–30 outer verticals, and 14–29 postorbitals. Clypeus with 38–58 setae. Tentorium 311– 326 m long, 64–86 m wide. Stipes 285–311 m long, 86 m wide. Palpomere lengths (in m): 90–94, 206–225, 319–424, 300–339, 319.

Thorax. Antepronotum with 78 setae. Acrostichals about 65–75, dorsocentrals about 65–100, prealars 50–61, median anepisternum II with 20–30 setae, preepisternum with 16– 22 setae. Scutellum with about 65–100 setae.

Wing. VR 0.94. Costal extension 120–150 m long, RM 188–195 m long, MCu 94– 120 m long, distance between MCu and RM 8– 19 m. Wing membrane with numerous setae in apical half. Cell m and anal lobe bare, cell r with 14–16 apical setae, r1 with 4, r2+3 with 7 setae, numerous setae each in cells r4+5, m1+2 and m3+4. Subcosta, RM, M and postcubitus bare, brachiolum with 8–12 setae, R with 58–78, R1 with 72–84, R2+3 with 7–15, R2 with 2–5, R3 with 12–16, R4+5 with 98–103 setae, costal extension with 14–20 non­marginal setae, M1+2 with about 35–55, M3+4 with about 50, Cu1 with about 20, An with about 30–50 setae. Squama with about 75–90 setae.

Legs. Spur of front tibia 109–128 m long, with 16–18 lateral teeth; spurs of middle tibia 98–109 and 79–94 m long, with 16 and 18 teeth, respectively; of hind tibia 109–146 and 86–109 m long, each with about 18 teeth. Width at apex of front tibia 120–131 m, of middle tibia 120–128 m, of hind tibia 135– 143 m. Hind tibial comb absent. Sensilla chaetica apparently absent. Lengths (in m) and proportions of legs:

– Derotanypus spp., 24–26: D. limbatus (Lundström) , comb. n., 24: male hypopygium, 25: female genitalia, ventral view, 26: female genitalia, dorsal view, 27–29: D. sibiricus (Kruglova & Chernovskii) , 27: male hypopygium, 28: female genitalia, ventral view, 29: female genitalia, dorsal view.

Hypopygium (Fig. 24). Tergite IX without posterior setae. Phallapodeme in two sclerotized, overlapping parts 161–173 m and 124–150 m long. Gonocoxite 428–506 m long. Gonostylus 278–323 m long, basal part 75–98 m wide, apical part 53–60 m wide in middle, tapering in apical third; megaseta 15–17 m long. HR 1.47–1.57, HV 2.43– 2.57.

FEMALE IMAGO (n = 1–2)

Total length 6.59–7.77 mm. Wing length 4.86–4.97 mm. Total length/wing length 1.36–1.56. Wing length/length of profemur 2.13. Coloration as in male.

Head. AR 0.19–0.22. First flagellomere (=Fm1) 71– 70 m long, Fm2 56 m, Fm3–12 each 68–86 m, Fm13 98–124 m, Fm14 188–225 m long. Temporal setae 68–69, consisting of 18–25 outer verticals; 25–29 inner verticals, and 18–22 postorbitals. Clypeus with 50–52 setae. Tentorium 349–364 m long, 45–73 m wide; stipes 263–338 m long, 14 m wide. Palpomere lengths (in m): 90–109, 176–188, 356, 330–356, 356.

Thorax. Antepronotum with 20–27 lateral setae. Acrostichals not countable, dorsocentrals about 115, prealars 80–85, median anepisternum II with 16–37 setae, preepisternum with 26–40 setae. Scutellum with about 100 setae.

Wing. VR 0.95. Costal extension 131–154 m long, RM 281–285 m long, MCu 105– 128 m long, distance between MCu and RM 8– 15 m. Wing membrane with numerous setae over whole wing, including anal lobe and costal cell. Cell r with 39–80 setae, cell m with 12–13 setae. Subcosta apparently bare, brachiolum with 10–14 setae, costal extension with 12–13 non­marginal setae, R with about 80–100, R1 with about 95–105, R2+3 with 27– 42, R2 with 13, R3 with 20–30, R4+5 with about 165–185, postcubitus with 5–6 setae, M with 0–1, M1+2, M3+4, Cu1 and An each with numerous setae. Squama with about 80–100 setae.

Legs. Spur of front tibia 113–116 m long, with 16–18 lateral teeth; spurs of mid tibia 124 m and 98 m long, with 20 and 17–18 teeth, respectively; one spur of hind tibia 113 m long with 20–22 teeth, the other spur lost. Hind tibial comb absent. Width at apex of front to hind tibiae (in m) as: 128–131, 131, 146. Sensilla chaetica about 45 in apical third of ta1 of mid leg, about 25 in apical third of ta1 of hind leg. Lengths (in m) and proportions of legs:

fe ti ta1 ta2 ta3 ta4 ta5 LR BV SV BR Genitalia (Figs. 25, 26). Sternite VIII with about 200 setae. Gonotergite IX bare, rudiments of gonocoxite weak to very weak. Segment X bare. Cercus 225–255 m long. Seminal capsule 225–236 m long including triangular neck, 169–199 m wide. Notum 338– 349 m long.

Remarks

The holotype of A. quadrinotata is considerably more pale than the specimens of D. limbatus . This is partly since the specimen is somewhat teneral. However, no significant differences could be found in any measurements.

The higher leg ratios all belong to the holotype of A. quadrinotata . The measurements of the front leg include only the lectotype of D. limbatus (the higher measurements except for ta4) and the lectotype of A. quadrinotata (the lower measurements). The higher BV and SV on the front leg belong to the lectotype of D. limbatus . Lundström gives the relative leg lengths of the two species. According to his measurements A. limbata should have a foreleg ratio of 0.59 and a SV of 3.27, A. quadrinotata a leg ratio of 0.65 with a SV of 2.92. However, not much confidence can be given to measurements made on unmounted specimens. According to Lundström A. limbata should be the smaller species when in fact it contains both the smallest and the largest specimen. The discrepancies between the dates concern the paralectotypes and thus do not effect the validity of the primary types.

Murray & Fittkau (1989, fig.5.13 F) illustrate a species which they call Derotanypus sp. nr. aclines (Sublette) . However, that species is lacking the transverse row of setae present posterior on tergite IX diagnostic for D. aclines and the nominal subgenus. Their species, however, could be conspecific with D. limbatus in the subgenus Merotanypus of Roback (1971).