Stenochironomus atlanticus Pinho & Mendes

Pinho, Luiz Carlos De, Mendes, Humberto Fonseca & Marcondes, Carlos Brisola, 2005, A new Brazilian species of Stenochironomus Kieffer mining decayed leaves in bromeliads (Diptera: Chironomidae), Zootaxa 1046, pp. 37-47 : 38-44

Stenochironomus atlanticus Pinho & Mendes new species

Type material: Holotype male with larval and pupal exuviae, BRAZIL: Santa Catarina State, Florianópolis, Unidade de Conservação Ambiental Desterro ( UCAD), 27°31’50,8”S, 48°30’44,3”W, 15.IX.04, in Canistrum lindenii (Regel) Mez, L.C. Pinho & M.H. Moraes. Paratypes: 1 male with larval and pupal exuviae, same data as holotype except 24.IV.05, in Vriesea vagans (L.B. Smith) L.B. Smith, L.C. Pinho ; 7 males, same data as holotype except 09.I­10.II.04, in Nidularium innocentii Lemaire, L.C. Pinho ; 1 male, same data as holotype except 19.IX­03.X.03, in N. innocentii, L.C. Pinho ; 1 male, same data as holotype except 0 3–24.X.03, in N. innocentii, L.C. Pinho ; 1 male, same data as holotype except 20.VIII–17.IX.04, in Neoregelia laevis (Mez) L.B. Smith, L.C. Pinho ; 1 male, same data as holotype except 20.VIII–17.IX.04, in Vriesea philippocoburgii Wawra ; 1 female with larval and pupal exuviae, same data as holotype except 24.IV.05, in Vriesea vegans (L.B. Smith) L.B. Smith, L.C. Pinho ; 2 females, same data as holotype; 2 females, same data as holotype except 09.I–10.II.04, in N. innocentii, L.C. Pinho ; 1 female, same data as holotype except 17.IX–17.X.04, L.C. Pinho; 1 female, same data as holotype except 20.VIII–17.IX.04, in N. laevis, L.C. Pinho ; 8 larvae and 3 pupae, same data as holotype.

Diagnostic characters: The male imago can be separated from all other Stenochironomus species by the combination of a very long inferior volsella; pale, rounded apex of tergite IX; AR 0.96–1.08; and slightly bulbous apex of the anal point. The female imago can be distinguished by the lack of dark pigmentation; dorsomesal lobes joined along the margin; and triangular ventrolateral lobe of gonapophysis IX. The pupa is distinguished by T VIII lacking shagreen; an interrupted row of hooklets on tergite II; the anal segment with an anterior pair of shagreen patches; the frontal apotome not elongated; and the large, deltoid­tipped anal lobe extending beyond the swim paddles. The larva can be separated from other Stenochironomus species by having the labral lamella with two groups of spicules arranged comblike; pecten epipharyngis with simple spicules arranged in a row; and procercus with about 8 filaments.

Etymology: The name atlanticus refers to Mata Atlântica, the Brazilian Atlantic Rain Forest, where the new species was collected.

Male. (n = 10, except when otherwise stated).

Total length 3.19–3.96, 3.58 mm. Wing length 1.46–1.77, 1.56 mm. Total length/wing length 2.08–2.42, 2.30. Wing length/length of profemur 1.49–1.63, 1.58. Coloration: body, wings and legs completely pale to yellowish.

Head ( Fig. 1 A). AR 0.96–1.08, 0.99. Thirteenth flagellomere 458–561, 492 µm long. Temporals 14–18, 17 in single row. Clypeus with 11–18, 14 setae. Tentorium, stipes, and cibarial pump as in Fig. 1 B. Tentorium 113–152, 135 µm long; 27–44, 34 m wide at sieve pore; 12–16, 15 µm wide at posterior tentorial pit. Stipes 147–174 (2) µm long; 5–8, 7 (3) µm wide. Palp segment lengths (in µm): 36–53, 44; 41–57, 49; 156–196, 171; 117–155, 134; 209–255, 235 (9).

Thorax ( Fig. 1 C). Acrostichals 10–19, 15; dorsocentrals 11–16, 13 in single row; prealars 4–6, 5. Scutellum with 9–14, 11 setae in single row. Anterior edge of scutum slightly rounded in lateral aspect.

Wing ( Fig. 1 D). VR 1.20–1.30, 1.25. Brachiolum with 2 setae. R with 28–48, 34; R1 with 26–36, 32; R4+5 with 48–70, 60; RM with 0–2, 1; M with 0–5, 2 setae; remaining veins bare. Squama with 3–5, 4 setae.

Legs. Scale of front tibia 32–50, 40 (4) µm long, with 2–3, 2 strong and 1–2, 2 weak setae; spurs of middle tibia 32–40, 35 (4) µm and 40–43, 41 (4) µm long; spurs of hind tibia 32–40, 35 (4) µm and 40–47, 44 (4) µm long. Apex of fore tibia 50–54, 53 (4) µm wide, of mid tibia 50–58, 56 (4) µm wide, of hind tibia 65–72, 67 (4) µm wide. Lengths (in µm) and proportions of legs as in Table 1.

Hypopygium ( Fig. 1 E–F). Anal point 91–114, 107 µm long; 6–8, 7 (8) µm wide 1/3 from apex; 10–13, 12 (8) µm wide at apex. Tergite IX with 18–25, 22 strong setae, caudal apex slightly rounded. Laterosternite IX with 3–5, 4 setae. Phallapodeme 76–93, 83 (9) µm long; transverse sternapodeme 20–25, 23 (9) µm long. Gonocoxite 136–164, 150 µm long; inferior volsella 149–192, 167 µm long, with 4–5, 5 setae; superior volsella 34–46, 42 µm long. Gonostylus 134–169, 154 µm long. HR 0.86–1.08, 0.98; HV 2.05–2.66, 2.33.

Female (n = 5, except when otherwise stated).

Total length 3.04–4.23, 3.64 mm. Wing length 1.50–2.27, 1.87 mm. Total length/wing length 1.70–2.31, 1.94. Wing length/length of profemur 1.40–1.47, 1.44. Coloration as in male.

Head. Flagellomere lengths (in µm): 135–183, 155; 93–129, 113; 86–120, 108; 69–105, 92; 84–159, 132. Longest seta 299–389, 337 µm long. AR 0.22–0.31, 0.28. Temporals 13–20, 17 in single row. Clypeus with 15–25, 20 setae. Tentorium 131–177, 151 µm long; 28–33, 30 µm wide at sieve pore; 14–18, 15 µm wide at posterior tentorial pit. Stipes 147–174 (2) µm long. Palp segment lengths (in µm): 36–58, 44; 51–67, 58; 162–234, 196 (4); 101–191, 151 (4); 216–329, 267 (4).

Thorax. Acrostichals 19–48, 31; dorsocentrals 14–26, 19 in single row; prealars 7–8, 7. Scutellum with 10–22, 15 setae in single row.

Wing. VR 1.20–1.29, 1.25. Brachiolum with 2 setae. R with 31–52, 42; R1 with 43–80, 57; R4+5 with 86–123, 94; RM with 1–4, 2; M with 3–10, 7 setae; remaining veins bare. Squama with 5–8, 6 setae.

Legs. Lengths (in µm) and proportions of legs as in Table 2.

fe ti ta1 ta2 ta3 ta4 ta5 LR BV SV BR

1065­1548, 779­1164, 1183­1706, 592­868­ 493­720, 434­621, 148­ 227, 1.41­ 1.52, 1.74­1.82, 1.54­1.64, 2.86­5.75, p1 1302 978 1436 740 609 529 191 1.47 1.80 1.59 3.91

878­1292, 779­1114, 513­730, 247­375, 187­286, 118­168, 0.64­0.72, 3.43­3.57, 2.99­3.39, 3.33­4.26, p2 59­79, 71

1089 953 633 316 231 142 0.66 3.52 3.22 3.81

986­1390, 937­1371, 690­1006, 375­562, 286­424, 167­237, 0.73­0.78, 2.79­2.91, 2.64­2.79, 4.09­5.91, p3 69­ 88, 83

1203 1148 862 477 361 205 0.75 2.85 2.72 4.96 Abdomen. Number of setae on tergites I–VIII as follows: 49–90, 62; 44–105, 71; 40–93, 67 (4); 47–89, 68; 38–99, 60; 24–92, 49; 21–72, 40; 11–32, 24. Number of setae on sternites I–VIII as follows: 5 (1); 6–12 (2); 6–59, 31 (4); 31–64, 44; 29–70, 46; 23–55, 41; 32–60, 44; 60–82, 72.

Genitalia ( Fig. 2 A–E): Tergite IX with 37–50, 43 setae; gonocoxite IX with 3–4, 4 setae. Cercus 86–114, 98 µm long. Gonapophysis IX notum 179–217, 200 µm long. Coxosternapodeme IX 68 –93, 80 µm long.

Pupa (n = 4, except when otherwise stated). Total length 3.88–5.38, 4.61 mm. Coloration: cephalothorax and abdomen transparent, except for first leg sheath and wing sheath brownish; base of wing sheath, prothoracic and metathoracic areas with brown spots; medial portion of T I and lateral portions of T II–VIII brownish.

Cephalothorax. Frontal apotome not elongated ( Fig. 3 A). Precorneal setae 2–3, 3; lamelliform; 26–65, 45 µm long ( Fig. 3 B). Dorsocentrals (Dc) 25–58, 41 µm long; lamelliform ( Fig. 3 C). Distance between Dc1 and Dc2 3 (1) µm; between Dc2 and Dc3 243 (1) µm; between Dc3 and Dc4 2 (1) µm.

Abdomen ( Fig. 3 D–E). T I bare; T II–IV with median, large field of shagreen; T V–VI, with anterior and posterior patches of shagreen, separated by fine shagreen; T VI with anterior and posterior patches of shagreen totally separated; T VII with single anteromedian field of shagreen; T VIII without shagreen; anal segment with anterior pair of shagreen patches. T II with interrupted row of hooklets. Abdominal setation: S I without L setae; S II–IV with 4 L setae; S V–VII with 4 LS setae; S VIII with 5 LS setae. Spur on S VIII with 1–3, 2 teeth (3), longest tooth 32– 45, 26 (3) µm long. Apex of anal lobe deltoid, extending beyond swim paddles; with 18–26, 23 filaments in fringe. Genital sac 107–120, 113 (3) µm long; anal lobe 205 (1) µm long.

Fourth­instar larva (n = 9, except when otherwise stated). Total length 6.92–8.27, 7.44 (8) mm. Head capsule ( Fig. 4 A–B), 0.38–0.42, 0.40 (7) mm long.

Head. Antenna as in Fig. 4 C; lengths of antennal segments (in µm): 43–54, 49; 14–19, 17; 3–6, 5 (8); 4–8, 6 (7); 1–2, 2 (8). Blade 18–23, 20 µm long. Labrum as in Fig. 4 D. Labral lamella with two groups of spicules arranged comblike, pecten epipharyngis with simple spicules arranged in row. S1 simple, 12–24, 21 (7) µm long; S2 simple to pinnate, 18–25, 21 (6) µm long. Premandible 40–55, 47 (8) µm long, with brush of about 30 setae. Mandible ( Fig. 4 E) 114–144, 128 µm long, with 4 inner teeth. Mentum ( Fig. 4 F) 86–95, 91 (8) µm wide, with median tooth 7–10, 8 (8) µm wide; paralabial plate with cuticular thickening along lateral edge. Labiohypopharynx ( Fig. 4 G) with ligular lobes rounded, with parallel–sided cleft between them.

Abdomen. Procercus with about 8 filaments, associated seta of equal size. Anal papillae ( Fig. 4 H) constricted medially, basal portion 145 (1) µm long, apical portion 222 (1) µm long. Anal hook 32–43, 38 (8) µm long.

Figures

FIGURE 1. Stenochironomus atlanticus Pinho & Mendes new species, male imago. A, head. B, cibarial pump, tentorium, and stipes. C, thorax. D, wing. E, anal point and tergite IX and dorsal aspect of left gonocoxite and gonostylus. F, hypopygium with anal point and tergite IX removed, left dorsal aspect, right ventral aspect.

FIGURE 2. Stenochironomus atlanticus Pinho & Mendes new species, female imago. A, genitalia, dorsal view. B, genitalia, ventral view. C, dorsomesal lobe. D, apodeme lobe of gonapophysis VIII. E, ventrolateral lobe of gonapophysis IX.

FIGURE 3. Stenochironomus atlanticus Pinho & Mendes new species, pupa. A, frontal apotome. B, basal ring of thoracic horn and precorneals. C, thorax. D, tergites I – V. E, tergites VI – IX.

FIGURE 4. Stenochironomus atlanticus Pinho & Mendes new species, larva. A, head capsule, dorsal aspect. B, head capsule, ventral aspect. C, antenna. D, labrum. E, mandible. F, mentum and paralabial plate. G, labiohypopharynx. H, anal end.