Stenochironomus messias, Reis, Emiliano De Angelis, Filho, Arlindo Serpa & Ferreira-Keppler, Ruth L., 2013

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: 454-458

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Stenochironomus messias

sp. n.

Stenochironomus messias   sp. n.

Figs 4–6 View FIGURE 4 View FIGURE 5 View FIGURE 6

Type material. Holotype, BRAZIL, Amazonas State, Presidente Figueiredo, BR 174, Km 107, Hotel Fazenda Marupiara, 02º 03’ 38,6 ”S, 60 º 06’ 60 ’’W, 19.X. 10, collected in submerged leaf, adult male with pupal and larval exuviae, 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: wedge-shaped apex of tergite IX, with two lateral robust protuberances covered with fine setae. The pupa is distinct by the presence of rounded small frontal warts; TVIII spur with four teeth, and the second internal teeth has more than twice the length of the remaining teeth.

Etymology. This species is honourably named after Dr. Maria Conceição Messias   , who was the first author’s supervisor and for her contribution to the knowledge of Brazilian Chironomidae   . The name should be treated as a noun in apposition.

Description. Adult male (n = 1)

Total length 5.00 mm. Wing length 2.33 mm. Wing length/length of profemur 1.52 mm.

Colour. Eyes markedly metallic green, whether kept alive or in ethanol. Antenna with light brown bristles and flagellomeres. Dark brown Postnotum in the ⅔ basal region, dark brown stripe at base of lateral vitae, dark brown median anepisternum, posterior anepisternum and mesepimeron, preepisternum with dark brown stripe in anterior region. Dark brown fore legs with apex to femur; fore tibia with dark brown spot in basal and apical region, fore tarsus 1 with a brown stripe in apical region, tarsus 2–5 damaged; mid legs with apex and basal regions of femur with dark brown stripes, mid tibia with a dark brown spot in the basal region, tarsus 1–5 without markings and hind legs with apex and posterior basal region of femur with dark brown stripes, hind tibia with dark brown marking in basal region, hind tarsus 1–5 damaged. Light brown wings with a large spot in middle region. Abdomen with dark brown spots on tergite I, located in laterodorsals region extending medially from the distal margin, forming a design of "U" (in dorsal view); tergites II –IV: brown band on posterior region; dark brown hypopygium dark in region of tergite IX, with inferior volsella and gonostylus varying from pale to brownish.

Head (as Figs. 1 View FIGURE 1 A; 1 B). AR 2.23, ultimate flagellomere 1038 µm long. Temporal setae 22. Clypeus with 27 setae. Tentorium 152 µm long; 9 µm wide at sieve pore; 11 µm wide at posterior tentorial pit. Stipes 53 µm long; 4 µm wide. Palpomere lengths (in µm): 72; 59; 207; 145; 242.

Thorax (as Fig. 1 View FIGURE 1 C). Ac 0; Dc 26; Pa 9; Scts 17 in two rows. Anterior edge of scutum slightly rounded in lateral aspect.

Wing (as Fig. 1 View FIGURE 1 D). VR 1.14. Brachiolum with 3 setae. R: 54 setae; R 1: 62 setae; R 4 + 5: 83 setae; remaining veins and bare squama.

Legs. Scale of fore tibia 59 µm long; spurs of mid tibia 50 µm; spurs of hind tibia 59 µm. Apex of fore tibia 73 µm wide, mid tibia 72 µm, hind tibia 69 µm. Lengths (in µm) and proportions of legs as in Table 2.

Hypopygium ( Figs. 4 View FIGURE 4 A; 4 B). Anal point short and wide, with a slightly narrowed apex, 148 µm long; 48 µm wide at base; 21 µm wide at apex. Tergite IX: 43 median setae, wedge-shaped apex, with 8 setae on each side of anal point, bearing two lateral dark brown protuberances covered with fine setae. Laterosternite IX: 3 setae. Phallapodeme 113 µm long; transverse sternapodeme 21 µm long. Gonocoxite 225 µm long; inferior volsella slender, 262 µm long, with 6 setae and single apical strong bristle; superior volsella 91 µm long. Gonostylus widest subapically, 274 µm long. HR 0.82; HV 1.82.

Pupa (n = 1, exuviae)

Total length 5.04 mm (wing sheath damaged). Colour: light brown cephalothorax and abdomen.

Cephalothorax. Elongated frontal apotome with two small rounded warts at lateral ends of frontal apotome ( Fig. 5 View FIGURE 5 A), absent wing tubercle. Wing sheath damaged; precorneals, dorsocentrals and median suture not visible.

Abdomen ( Fig. 5 View FIGURE 5 B). TI bare; TII –V: median, large field of shagreen; TVI: field of shagreen restricted to two patches on anterior and posterior regions; TVII –VIII: bare. TII: posterior row of continuous hooklets in posterior middle with 327 µm long. Abdominal setation: SI: no L setae; SII –IV: 3 L setae; SV –VII: 4 LS setae; SVIII: 5 LS setae. Pedis spurii B absent. Spur on SVIII with 4 brownish teeth ( Fig. 5 View FIGURE 5 C). Genital sac with 211 Μm long, not exceeding apex of anal lobe; apex of anal lobe rounded, with a fringe of 45 filaments.

Fourth-instar larva (n = 1, exuviae)

Head. Head capsule 0.47 mm long. Lengths of antennal segments (in Μm): 64; 28; segments 3–5 damaged. Labrum damaged. Mandible ( Fig. 6 View FIGURE 6 B) 164 Μm long, containg 4 inner teeth. Mentum ( Fig. 6 View FIGURE 6 A) 251 Μm wide and convex, with 10 blackish teeth; micropore not observed; paralabial plate with a light concavity next to the mentum, absent striae. Base of dorsolateral strip originating from the base of dorsomedian strip. Labiohypopharynx damaged.

Female unknown.

Distribution and habitat. This species is only known to north of Brazil, Amazonas State, municipality of Presidente Figueiredo. The larva was collected in a submerged leaves in a rocky bottom stream of a permanent water flow.

Remarks. Adult males of Stenochironomus messias   sp. n. and Stenochironomus oliveirai   sp. n. resemble in having the same pattern of colour of the thorax and abdomen, and by the presence of well-produced posterolateral protuberances of tergite IX. These structures do not occur in any other species of the genus. These two species can be separated by colour of the fore and hind leg tibiae, shape of protuberances and apex of tergite IX and the width of anal point (see diagnoses).

Pupae of the two new species can be easily separated by the shape of the spur on tergite VIII, the length of genital sacs and the pattern of shagreen. These species were not placed in any of the subgenera proposed by Borkent (1984). The larva of Stenochironomus oliveirai   sp n. shows dorsolateral strip originating from near the half of dorsomedian strip. This feature was suggested as the main diagnostic character for wood trunk miners (subgenus Stenochironomus   ), however, is not confirmed in this case.

TABLE 2. Lengths (in µm) and proportions of leg segments of Stenochironomus messias sp. n., male (n = 1).