Stenochironomus reissi Borkent, 1984

Reis, Emiliano De Angelis, Filho, Arlindo Serpa & Ferreira-Keppler, Ruth L., 2013, Two new species and records of Stenochironomus Kieffer from Brazilian Amazon region, with description of immature stages (Diptera: Chironomidae), Zootaxa 3710 (5), pp. 449-466 : 458-461

Stenochironomus reissi Borkent, 1984

Figs 7–8

Stenochironomus reissi Borkent, 1984: 128 ; Spies & Reiss 1996: 73.

Material examined. BRAZIL, Amazonas State, Presidente Figueiredo, BR 174, Km 107, Hotel Fazenda Marupiara, 02º 03’38,6”S, 60º 06’60’’W, 19.X.10, two adult males with pupal and larval exuviae, collected in submerged leaf, leg. E.D. De-Angelis-Reis (INPA, slide-mounted in Euparal).

Diagnostic characters. The adult male can be separated from all other Stenochironomus species by the following combination of characters: anal point thin and straight in dorsal view; superior volsella with setae restricted to basal half, except for an apical setae; lacking dark pigmentation in the body. The pupa is distinct in having tergite VII with a large pair of spurs on the lateral posterior region.

Pupa (n = 2, exuviae, except when counted differently)

Total length 3.90 (1) mm. TI and anal lobe damage. Colour: Light brown cephalothorax and abdomen.

Cephalothorax. Frontal apotome elongated with rounded frontal warts ( Fig. 7 A), absent wing tubercle. Precorneal damaged. Dorsocentrals (Dc) 21–23 (1) µm long. Distance between Dc1 and Dc2:1 (1) µm; Dc2 and Dc3: 128 (1) µm; Dc3 and Dc4: 1,5 (1) µm; median suture granulose ( Fig. 7 C).

Abdomen ( Fig. 7 B). TI damaged; TII–V: median, large field of shagreen; TVI: field of shagreen restricted to anterior, middle and posteromedian regions; TVII: bare with a large pair of spurs on posterior lateral region; TVIII: bare; anal segment with an anterior pair of rounded shagreen patches. TII: posterior row of continuous hooklets in posterior middle and divided in two groups of hooklets 84 (1) and 68 (1), by a distance of 37 (1) µm. Abdominal setation: SI: with no L setae; SII–IV: 3 L setae; SV: 3 LS setae; SVI–VII: 4 LS setae; SVIII: 5 LS setae. Spur on SVIII with 2–4 brownish teeth ( Fig. 7 D). Genital sac 155 (1) Μm long, overreaching apex of anal lobe by 63 (1) Μm; apex of anal lobe rounded, with a fringe of 16 (1) filaments.

Fourth-instar larva (n = 2, exuviae, except when counted differently).

Head. Head capsule 0.40–0.55 mm long. Antenna ( Fig. 8 A); lengths of antennal segments (in Μm): 44–72; 15– 31; 5–15; 6–12; 3–4. Antennal blade 21–28 Μm long overreaching second segment. Labrum damaged. SI simple, 19 (1) µm; SII palmate, 10 Μm long; SIII simple, 8 (1) Μm long. Mandible ( Fig. 8 B) 101–148 Μm long, with 3 inner teeth and 1 dorsal tooth. Mentum ( Fig. 8 C) 83–125 Μm wide and convex, with 10 blackish teeth; micropore placed posteriorly to setae submenti; paralabial plate with strong concavity next to mentum and a few striae. Base of dorsolateral strip originating next to to the base of dorsomedian strip. Labiohypopharynx ( Fig. 8 D) with rounded ligular lobes, with a narrow cleft between the lobes, nearly parallel-sided to the U-shaped structure. Female unknown.

Remarks. Stenochironomus reissi was, so far, known only to Brazil in the Amazonas and Pará States. The larvae were obtained from mined submerged leaves in a rocky bottom small river, with dense riparian vegetation. The adults were obtained by laboratory rearing. S. reissi is close to S. impendens Borkent, 1984 and S. leptopus Borkent, 1984 showing a similar shape of apex of tergite IX that is square-shaped in dorsal view. Despite these similarities, S. reissi can be separated by the apical setae of inferior volsella, that is short and robust, while in other species it is long and slender. The presence of a broad pair of spurs in posterior lateral region of tergite VII in pupa is known only from this species.

Figures

FIGURE 7. Stenochironomus reissi Borkent, 1984, pupa. A—frontal apotome, B—abdomen: tergites I – IX, C—cephalothorax, D—spur on T VIII. E—basal ring of thoracic horn.

FIGURE 8. Stenochironomus reissi Borkent, 1984, larva. A—antenna, B—mandible, C—mentum and paralabial plate, Dlabiohypopharynx,