Orthocladius (Orthocladius) nitidoscutellatus

Saether, Ole A., 2005, A new subgenus and new species of Orthocladius van der Wulp, with a phylogenetic evaluation of the validity of the subgenera of the genus (Diptera: Chironomidae), Zootaxa 974, pp. 1-56 : 50-51

Orthocladius (Orthocladius) nitidoscutellatus

( Figs. 29, 30 , 39, 40 )

Orthocladius nitidoscutellatus Lundström, 1915: 11

Orthocladius trigonolabis Edwards, 1924: 170 .

Orthocladius aquilonaris Goetghebuer, 1940: 63 .

Trichocladius thienemanni Thienemann 1941: 217 , not Goetghebuer 1940: 69. Orthocladius (Orthocladius) nitidoscutellatus Lundström ; Saether 2004 c: 14.

Material examined

NORWAY: Svalbard, Danskøya, Lake Arresjøen, 2 ɗ reared from pupa, 1 mature ɗ pupae, 2 prepupa larvae, 14 viii 1993, Ø. A. Schnell ( ZMBN); Svalbard, Vasa Peninsula, Lake Birgersjøen, ɗ reared from pupa, 15 viii 1993, Ø. A. Schnell ( ZMBN); Svalbard, Ny Friesland, Lake N. Mosselvatn, pupal exuviae, 27 viii 1977, H. A. Støen ( ZMBN); Oppland, Vågå, Lake Nedre Sjodalsvatn, 1 mature ɗ pupa reared from larva, 26 v 1990, Ø. A. Schnell ( ZMBN).

Male imago

The description in Soponis (1977: 96) can be supplemented by the presence of about 6 sensilla chaetica at the base of ta1 of the mid leg and sensilla chaetica apparently absent from the hind leg.

Pupa (n = 3)

The description in Soponis (1977: 99) and Langton & Visser (2002) and Rossaro et al (2003: 234) can be supplemented by:

Total length about 4.7–5.7 mm.

Cephalothorax. Frontal setae 94–120 mm long. Thoracic horn with sparse points over most of its length [bare according to Soponis (1977), with a few apical points according to Langton & Visser (2002), with points in apical half according to Rossaro et al. (2003)], 195–218 µm long; 32–41 µm wide; 4.73–6.82 times as long as wide; 10.88–1.02 times as long as anal macrosetae. Precorneal setae 114–188 µm long. Anterior dorsocentral (Dc1) 83–90 µm long, Dc2, 75–94 µm, Dc3 68–79 µm, Dc4 34–49 µm long. Distances (in µm): Dc1–Dc 2 30–86, Dc2–Dc3 83–109, Dc3–Dc 4 28–41.

Abdomen. With 31–62 caudal hooklets on tergite II in 4–5 rows in specimens from Lake Arresjøen, only two rows in the other specimen. Segments II–VI each with 3 L setae , VII with 4, VIII with 5 L setae . Lengths of L1–L5 on segment VIII in µm as: 64–94, 75–94, 79–86, 124–128, 131–154.

Anal lobe 329–371 µm long. Anal macrosetae 214–225 µm long. Male genital sac conspicuous, overreaching anal lobe by 56–68 µm, about 86 µm wide at apex.

Fourth instar larva (n = 2–3 except when otherwise stated)

Total length about 5.0– 6.1 mm. Head capsule 0.43–0.45 mm long. Postmentum 195– 199 µm long. Head capsule yellowish brown.

Head. Antenna as in Fig. 29 . Length of antennal segments (in µm): 57–62, 14–17, 6–8, 4–6, 4–6. AR 1.36–2.08. Ring organ 7–9 µm from base, basal setal mark 14–19 µm from base, apical setal mark 50 µm (1) from base. Basal antennal segment 19–21 µm wide, blade 21–31 µm long, accessory blade 12–20 µm long. Lauterborn organs well developed, 7–8 µm long, style 7–9 µm long. Labrum ( Fig. 30 ) with 12–14 chaetae and 6 spinulae. Chaetulae laterales apparently all smooth. Premandible ( Fig. 30 ) simple with distinct apical notch, 92–95 µm long, brush absent. Mandible ( Fig. 39 ) 169–173 µm long, seta interna of about 7 smooth branches. Mentum ( Fig. 40 ) 150–161 µm wide, median tooth 11–12 µm wide, about twice as wide as first lateral tooth; ventromental plate 6 µm wide.

Abdomen. Claws of anterior parapods strongly serrated. Posterior parapods 284–331 µm long. Procercus 38–41 µm high, 30–38 µm wide. Anal setae 578–614 µm long, supraanal seta 131–143 µm long, 0.58 times as long as anal setae . Longer anal tubules 150–169 µm long, 71–86 µm wide at base.

Remarks. The larva from Lake Nedre Sjodalsvatn has a considerably longer antennal flagellum than the ones from Svalbard, resulting in a lower antennal ratio. In other details, however, it is nearly identical.

Figures

FIGURES 28 – 34. Orthocladius spp., larvae, 28: Orthocladius (Mesorthocladius) frigidus (Zetterstedt) labrum, epipharyngeal area and premandible, 29, 30: Orthocladius (Orthocladius) nitidoscutellatus Lundström, 29: antenna, 30: labrum, epipharyngeal area and premandible, 31, 32: Orthocladius (Mesorthocladius) lamellatus sp. n., 31: antenna, 32: labrum, epipharyngeal area and premandible, 33 – 34: Orthocladius (Mesorthocladius) nimidens sp. n., 31: antenna, 32: labrum, epipharyngeal area and premandible.

FIGURES 35 – 40. Orthocladius spp., larvae, 35, 36: Orthocladius (Mesorthocladius) lamellatus sp. n., 35: mandible, 36: mentum, 37 – 38: Orthocladius (Mesorthocladius) nimidens sp. n., 37: mandible, 38: mentum, 39 – 40: Orthocladius (Orthocladius) nitidoscutellatus Lundström, 39: mandible, 40: mentum