Stenochironomus annulus Song & Qi, 2022

Song, Chao, Zhu, Bin-Qing, Moubayed-Breil, Joel, Lei, Teng & Qi, Xin, 2022, Taxonomic study on the genus Stenochironomus Kieffer from the Baishanzu Nature Reserve, China (Diptera, Chironomidae), ZooKeys 1104, pp. 93-113 : 93

Stenochironomus annulus Song & Qi sp. nov.

Figs 3 , 4 , 5

Type material.

Holotype (BOLD & TZU sample ID: ZJCH220; Field ID: BSZ87) 1 male, China, Zhejiang Province, Lishui City, Qingyuan County, Baishanzu National Nature Reserve, 27.76°N, 119.31°E, 11-12. VIII. 2020, light trap, Qi X & Song C. Paratypes: 2 males, same data as for holotype.

Diagnostic characters.

The adult males of S. annulus sp. nov. can be separated from known Stenochironomus species from China by the following combination of characters: spots on the membrane of wing restricted to RM and FCu areas; posterior portion of median vittae with little pale pigmentation; lateral vittae with stripe markings; postnotum with markings reaching the posterior margin; femur of mid and hind legs with an Stenochironomus annulus medially on each; superior volsella cylindrical, with four long setae; inferior volsella extending beyond apex of anal point, with two or three bristles and one well-developed terminal spine.

Etymology.

The specific name refers to the circular ring markings of the femur of mid and hind legs of the male adult.

Description.

Male imago (N = 3). Total length 3.59-4.17, 3.87 mm. Wing length 1.95-2.03, 2.00 mm. Total length / wing length 1.75-2.05, 1.94. Wing length / length of pro-femur 1.58-1.93, 1.73.

Coloration (Fig. 3 ). Mature adult mostly brownish. Head yellow. Thorax yellowish except for the lateral vittae, postnotum with dark pigmentation and medial lateral with light pigmentation (sometimes difficult to observe). Membrane with 2 dark spots restricted to RM and FCu areas. Legs. Apical 3/5 of femur of P1 dark brown; apical and annulus of femur, and Ta 5 P2-P3 dark brown; basal 1/2 of tibia of P3 dark brown. Abdomen. Tergites V-IX brown.

Head. AR 1.62-1.88 (2), ultimate flagellomere 680-770 µm long; Temporals 10-13, 12 setae including 5-8 inner, and 2-3 outer, verticals, postorbitals 1-3. Clypeus with 15-22, 19 setae. Tentorium 170-205 μm long, 45-53 μm wide at the widest part. Palp 5-segmented, lengths (in μm) of segments: 60-70, 66; 50-70, 60; 193-220, 203; 140-160, 152; 208-288, 248. Palpomere ratio (5th / 3rd) 1.09-1.31, 1.22.

Thorax. Dorsocentrals 16-17, 18; acrostichals 12-15, 14; prealars 5-6, 6; Scutellum with 11-13 setae in 2 rows.

Wing (Fig. 4A ). VR 1.08-1.08, 1.06. Brachiolum with 2-3 setae. Distribution of setae on veins: R, 31-39, 34; R1, 28-40, 34; R4+5, 33-62, 46. Squama with 8-12, 10 setae. Anal lobe normally developed.

Legs (Fig. 4D ). Fore leg: width at apex of tibia 43-50, 46 μm, tibia with blunt scale 35-40, 38 µm long. Mid leg: width at apex of tibia 53-65, 59 μm, tibia with 2 apical spurs 35-38, 37 and 40-45, 43 µm long. Hind leg: tibia 60-73 μm width at apex; tibial spurs 40-43, 42 and 40-43, 42 µm long, slightly fused medially. Lengths (in μm) and proportions of legs in Table 3 .

Hypopygium (Figs 4B, C , 5 ). Anal point straight and parallel-sided in dorsal view, 103-113, 100 μm long and 30-43, 35 µm wide at base, 8-10, 9 µm wide at apex. Tergite IX with 19-22, 20 long setae medially and posterior margin of tergite IX with 6 strong setae and 5 spines. Laterosternite IX with 4-4, 4 setae. Transverse sternapodeme 43-50, 47 μm long; phallapodeme 78-88, 85 μm long. Gonocoxite 173-185, 181 μm long, gonostylus 205-270, 238 μm long. Superior volsella cylindrical, 40-45, 43 μm long, 20-20, 20 μm wide, with 4-5 long setae (Fig. 4C ). Inferior volsella elongate, 203-228 μm long, extending beyond the apex of anal point, with 2-3 long bristles and 1 strong terminal spine. HR 0.64-0.90, 0.77, HV 1.46-1.75, 1.64.

Immature stages and female unknown.

Remarks.

Morphologically, S. annulus sp. nov. shows high similarity to Stenochironomus xianjuensis Zhang, Gu, Qi & Wang, 2016, on the basis of the following similar common characters: membrane of wing with similar spot patterns; cylindrical superior and inferior volsella. However, the new described species could be distinguished in having a straight and parallel-sided anal point and different leg pigmentation patterns. According to the molecular data, S. annulus is sister to S. gibbus (Fig. 1 ), but could be separated by thorax vittate and leg coloration (Table 4 ).

Distribution.

The species is currently known only from Zhejiang Province in Oriental China.

Figures

Figure 1. Neighbour-joining tree for twelve species of Stenochironomus based on K 2 P distance in DNA barcodes. Clade in yellow represents S. annulus sp. nov., red represents S. baishanzuensis sp. nov. Numbers on branches represent bootstrap support (> 75 %) based on 1000 replicates; scale equals K 2 P genetic distance.

Figure 3. Male adult (holotype, in lateral view) of Stenochironomus annulus Song & Qi sp. nov.

Figure 4. Male adult of Stenochironomus annulus Song & Qi, sp. nov. A wing B hypopygium in dorsal view C hypopygium in ventral view D legs.

Figure 5. Male adult (holotype) of Stenochironomus annulus Song & Qi sp. nov. A hypopygium in dorsal view B hypopygium in ventral view C superior volsella.