Chironomus lundstroemi, Saether, Ole A., 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 : 3-6

Chironomus lundstroemi sp. n.

( Figs. 1, 2, 7 )

Chironomus staegeri Lundb. sensu Lundström (1915: 6) , not Lundbeck, 1898

Type material. Holotype ɗ: RUSSIA: Chara­Ullach Mts., 30 vi 1902, M. I. Brussnew. Paratype: Ψ, Jana area, Seljach river, 3–7 vi 1908 [21 (8) vi 1908 in Lundström], K. A. Wollosowitsch. Both deposited at Zoological Institute, Russian Academy of Science, St. Petersburg.

Diagnostic characters. The male imago is characterised by a broad anal point tapered from base to tip; large frontal tubercles with conspicuous microtrichia with distinct bases, frons also densely microtrichiose; superior volsella tapering to a point, but with a distinct apical fold; fore leg ratio about 1.14; antennal ratio about 5.0; about 80 dorsocentrals and about 60 scutellars. The female imago has about 98 sensilla chaetica on mid ta1 and at least 75 on hind ta1; gonocoxite with 8 setae, tergite IX with 114 setae and segment X with 16 setae.

MALE IMAGO (n = 1)

Total length 8.33 mm. Wing length 5.15 mm. Total length/wing length 1.62. Wing length/length of profemur 3.01. Coloration brown with darker markings; abdomen with darker longitudinal, median band on all tergites.

Head. AR 5.00. Ultimate flagellomere 1843 m long. Dorsal interocular distance 189 m, ventral interocular distance 340 m. Frontal tubercle 45 m high, 15 m wide, with conspicuous microtrichia with distinct bases. Frons with dense and long microtrichia only posterior near tubercles, shorter and more scattered anteriorly. Temporal setae 36, consisting of 12 inner verticals, 12 outer verticals and 12 postorbitals. Clypeus with about 75 setae. Tentorium 360 m long, 94 m wide; stipes 345 m long, 180 m wide. Palpomere lengths (in m): 105, 113, 360, 311, 420. Third palpomere with 4 thin, lanceolate, 38 m long sensilla clavata.

Thorax. Antepronotal setae apparently absent. Acrostichals not countable, dorsocentrals about 80, prealars 19, supraalars 2. Scutellum with about 60 setae.

Wing. VR 1.01. Brachiolum with 4 setae, R with 26, R1 with 34, R4+5 with 7 setae, other veins bare. Squama with 39 setae.

Legs. Scale of front tibia 63 m long, spurs of mid tibia 94 and 49 m long including combs, hind leg lost. Width at apex of front tibia 116 m, of mid tibia 135 m. Lengths (in m) of fe to ta2 of front leg: 1713, 1900, 2170, 1096. LR of front leg 1.14, SV of front leg 1.66. Length of fe of mid leg 2018 m, of mid tibia 1947 m.

Hypopygium ( Fig. 1 ). Tergite IX with about 12 median setae and about 32 setae lateral to and underneath anal point; laterosternite IX with 10 setae. Anal point 131 m long, 75 m wide. Phallapodeme 300 m long, transverse sternapodeme 75 m long. Gonocoxite 300–341 m long; superior volsella 188 m long, 38 m wide (maximum width) about 1/ 3 from apex, with 8 basal setae; inferior volsella 319 m long, with 30 strong setae. Gonostylus 338 m long. HR 1.17, HV 2.46.

FEMALE IMAGO (n = 1)

Total length 7.98 mm. Wing length 4.62 mm long. Total length/wing length 1.73. Wing length/length of profemur 2.81. Coloration as in male, but abdomen without distinct median longitudinal band.

Head. AR 0.44. Flagellomere lengths (in m): 225, 158, 150, 150, 285. Dorsal interocular distance 180 m, ventral interocular distance 416 m. Frontal tubercle ( Fig. 2 ) 45 m high, 15 m wide, with conspicuous microtrichia as in male. Frons as in male. Temporal setae 45, consisting of 18 inner verticals, 10 outer verticals and 17 postorbitals. Clypeus with 90 setae. Tentorium 311 m long, 83 m wide; stipes 327 m long, 101 m wide. Palpomere lengths (in m): 90, 105, 311, 300, 506. Third palpomere with 5 lanceolate sensilla clavata.

Thorax. Antepronotal setae apparently absent. Acrostichals about 50, dorsocentrals about 80, prealars 12, supraalars 2. Scutellars not countable.

Wing. VR 0.98. Brachiolum with 3 setae, R with 29, R1 with 26, R4+5 with 24 setae, other veins bare. Squama with 37 setae.

Legs. Scale of front tibia 56 m long, spurs of mid tibia both 79 m long including combs, spurs of hind tibia both 90 m long including combs. Width at apex of front to hind tibiae (in m) as 113, 113, 150. Sensilla chaetica about 98 on ta1 of mid leg, at least 75 on ta1 of hind leg. Lengths (in m) and proportions of legs:

Abdomen. Tergite VIII with about 90 setae. Sternite VIII with 120 median setae and apparently no lateral setae.

Genitalia ( Fig. 7 ). Gonocoxite with 8 setae. Tergite IX with 114 setae. Segment X with 16 setae. Cercus 323 µm long. Seminal capsule 225 µm long not including 15 m long neck, 150 µm wide. Notum 304 µm long.

Remarks

The anal point is much wider and shorter than in C. staegeri Lundbeck as redescribed by Wülker et al. (1971). The species keys to couplet 15 in Lindeberg & Wiederholm (1979), but the anal tergite does not have a distinct reticulated pattern laterally. The male and female, although not from the same locality, appear to be conspecific as indicated by the characteristic frontal tubercles and especially the high chaetotaxy even when compared to the large size. The species differs from Chironomus aberratus Keyl , C. sororius Wülker , C. striatus Strenzke ; C. melanotus Keyl , C. lacunarius Wülker and C. riihimakiensis Hirvenoja (Wülker 1973, Wülker & Klötzli 1973, Hirvenoja & Michailova 1991) the species mentioned in couplet 15 of Lindeberg & Wiederholm (1979) as well as from most other species of the genus by the broad anal point. The anal point, however, is not as broad as in Chironomus obtusidens Goetghebuer and C. sp. a in Pinder (1978). C. tuvanicus Kiknadze et al., 1993 , a species in the riihimakiensis group which is said to comprise a number of northern Palaearctic species, including several in Siberia, has a nearly equally broad anal point. However, even taking into consideration a slightly smaller size, a much lower chaetotaxy with, for instance, only 27–36 dorsocentrals. The antennal ratio of C. lundstroemi is higher, the leg ratio lower and the setae of the thorax considerably more numerous than in any of the species mentioned above. The number of sensilla chaetica on the female tarsi is intermediate between the number found in C. melanotus and that found in C. riihimakiensis . The shapes of the ventrolateral and dorsomesal lobes of gonapophysis VIII are very similar to those illustrated by Hirvenoja & Michailova (1991: fig. 5) for C. melanotus .

Figures

FIGURES 1 – 10. Chironomus (Chironomus) spp., imagines, 1: C. lundstroemi sp. n., hypopygium, 2 – 6: frontal tubercles and frons, 2: C. lundstroemi sp. n., female, 3 – 4: C. trabicola Shobanov, Wülker & Kiknadze, female and male, 5: C.? lugubris Zetterstedt, female, 6: C. flavoviridis Lundström, female, 7 – 10: female genitalia, apodeme lobe (shown separately), dorsomesal and ventrolateral lobes, 7: C. lundstroemi sp. n., 8: C.? lugubris Zetterstedt, 9: C. flavoviridis Lundström, 10: C. trabicola Shobanov, Wülker & Kiknadze.