Chironomus (Lobochironomus) bifidus Pal et Hazra, 2017

Pal, G. & Hazra, N., 2017, Description of Chironomus bifidus sp. n. and first record of Ch. crassiforceps (Kieffer, 1916) from India (Diptera: Chironomidae: Chironominae), Far Eastern Entomologist 338 (338), pp. 10-15 : 11-14

Chironomus (Lobochironomus) bifidus Pal et Hazra , sp. n.

Figs 1–9

TYPE MATERIAL. Holotype: male with pupal exuviae [reared] India: West Bengal:

Malda, Gour [24°90´N, 88°11´E], 04.I 2016, leg. G. Pal (Type no. B. U. Ent. 293). Para-

types: 5 males, the same data as holotype .

DESCRIPTION. MALE (n = 6) ( Figs 1–4 ). Total length 4.38–5.69 mm; wing length

2.68–2.9 mm; total length/wing length 1.66–2.12; wing length/length of profemur 2.22–2.28.

Coloration. Thorax brown. Abdomen brown with few setae. Wing transparent.

Head. Eyes bare with 65–73 μm long dorsomedian parallel sided extension. Temporal setae 11–14 (IV 2–4, OV 2–3, Po 3–4). Frontal tubercle present. Clypeus with 11–16 setae on each side. Tentorium 100–166 μm long and 33–42 μm wide at sieve plate. AR 3.75–4.5;

ultimate flagellomere 1056–1220 μm long; total antennal length 1300–1545 μm. Length ratio of palpomeres (I–V) (μm): 81–130, 81–114, 81–114, 97–114, 49–81. CA 0.51–O.55, CP

1.61–2.04.

Thorax. Acrostichals 10–12; antepronotals 6–10. dorsocentrals 5–6 setae; prealars 4–7;

scutellum 8–10 setae.

Hypopygium ( Fig. 3 ). Base of anal point broad, apex moderately swollen, 85–97 μm long and 33–35 μm wide. Anal tergite band T–shaped. Lateral sternapodeme 81–114 μm long,

transverse sternapodeme 163–295 μm long. Gonocoxite 123–244 μm long bearing 6–8 setae at outer side. Gonostylus 144–195 μm long with 18–20 inner subapical setae arranged in two parallel rows, few of which apically split. Superior volsella ( Fig. 4 ) 123–195 μm long,

moderately projected posteriorly, swollen apically without any seta, microtrichiose; beaklike apicomedian projection 56–88 μm long, 1.5–2 times as long as the average width of basal portion. Inferior volsella 185–195 μm long, parallel–sided with 10–12 dorsal split setae. HR

0.85–1.25, HV 2.9–3.1.

FEMALE. Unknown.

PUPA (n = 1) ( Figs 5–9 ). Total length of exuviae 6.8 mm. Colouration. Light brown.

Dark brown margin at wing sheath, origin of antenna and margin of tergites.

Cephalothorax. Frontal apotome ( Fig. 5 ) 405 μm long and 324 μm wide. Cephalic tubercle not prominent with 8 μm long one apical seta. Frontal wart absent. Thoracic horn plumose arising from kidney shaped basal ring ( Fig. 6 ), 113 μm long and 82 μm wide.

Antennal sheath 1.78 mm long. Wing sheath 1.77 mm long.

Abdomen ( Fig. 7 ). Tergites I, VII and VIII bare. T II–VI with uniform shagreen. Con-

junctive III/IV with L setae. T II with 3 pairs of L setae at 0.2, 0.4 and 0.6 of segment length.

T II with hookrow consisting of ca 54–56 hooklets occupying 0.75 of segment width. Pedes spurii A and B present. T III with 4 pairs of L setae at 0.2, 0.4, 0.6 and 0.8 of segment length.

T IV with 4 pairs of L setae at 0.2, 0.4, 0.6 and 0.8 of segment length. T V with 4 pairs of LS

setae at 0.1, 0.2, 0.3 and 0.7 of segment length. T VI with 4 pairs of LS setae at 0.2, 0.3, 0.6

and 0.8 of segment length. T VII with 4 pairs of LS setae at 0.2, 0.43, 0.6 and 0.8 of segment length. TVIII ( Fig. 8 ) with 5 LS setae placed 0.2, 0.3, 0.4, 0.6, and 0.8 of segment length.

Caudolateral comb ( Fig. 9 ) deep brown with 3–4 stronger spines, none dominant.

Approximately 80 taeniae on anal lobe ( Fig. 8 ) and dorsal seta absent.

DIAGNOSTIC CHARACTERS. The new species can be distinguished by the following characteristics: Male. i) Anal point with broad base tapering to moderately swollen apex, ii)

gonostylus with inner subapical setae arranged in two parallel rows, few of which apically split, iii) superior volsella with microtrichia moderately projected posteriorly, swollen apically,

iv) beaklike apicomedian projection of superior volsella without any seta and v) inferior volsella parallel sided with dorsal split setae; Pupa. i) Cephalic tubercle not prominent with one apical seta and ii) caudolateral comb with 3–4 stronger spines, none dominant.

ETYMOLOGY. The name “ bifidus ” refers to Latinized version of dorsal split setae of inferior volsella.

DISTRIBUTION. Known only from India.

REMARKS. The new species bears similarity with Chironomus (Lobochironomus)

dorsalis Meigen (1818) in the shape of anal point and inferior volsella, but differs in the shape of gonostylus and superior volsella in adult male. It also shows similarity with C. (Lobochironomus) austini Beck and Beck (1970) in the shape of anal point and inferior volsella, but differs in the shape of gonostylus and superior volsella of adult male; the shape of caudolateral comb of pupa also differs.

NEW RECORD

Figures

Figs. 1–4. Chironomus bifidus sp. n., adult male. 1 – wing; 2 – fore tibial scale; 3 – hypopygium; 4 – superior volsella.

Figs. 5–9. Chironomus bifidus sp. n., pupa. 5 – frontal apotome; 6 – basal ring; 7 – tergites I–VII; 8 – tergite VIII with anal lobe and male genital sac; 9 – caudolateral comb.