Demicryptochironomus (Irmakia) dividuus Mukherjee et Hazra, 2022

Mukherjee, Bindarika & Hazra, Niladri, 2022, Two new species of Demicryptochironomus Lenz, 1941 from India with tentative phylogenetic relationship and a revised world key to known males (Diptera: Chironomidae), Zootaxa 5175 (1), pp. 88-100 : 92-95

Demicryptochironomus (Irmakia) dividuus Mukherjee et Hazra , sp. n.

urn:lsid:zoobank.org:act:860D8812-98E8-4B14-ADBB-9E15BF1BFE63

GenBank Accession No. ON881144

Material examined. Holotype male, labelled ‘ Holotype Demicryptochironomus (Irmakia) dividuus sp. n., India, West Bengal, Darjeeling [26.7095° N, 88.3542° E], 04.ix.2021, Coll. G. Pal’ . Paratype 1 male, labelled ‘ Paratype Demicryptochironomus (Irmakia) dividuus sp. n., India, West Bengal, Burdwan [23.2393° N, 87.8512° E], 26.ii.2021, Coll. N. Hazra’ .

Diagnostic characters. The species can be separated from other species of the genus Demicryptochironomus (Irmakia) by the following combinations of features: partially divided superior volsella at apex, and apically pointed gonostylus with strong concavity.

Etymology. The name “ dividuus ’’, a Latin word, refers to the partly divided superior volsella at apex.

Male (n=2)

Total length 2.4–3, 2.7 mm. Wing length 1.85–1.87 mm. Costal length 1.78 mm. Antennal length 0.8 mm.

Colouration. Thorax yellowish brown, leg colour light brown, abdomen yellow to light brown.

Head. Head width 500–540 µm. Temporal setae 8–10 (IV 1, OV 6–7, Po 0–2). Clypeal setae 9–10. Frontal tubercles present, 4.6–5 µm long. Eyes bare with dorsomedial extension of 115–130 µm. Ultimate flagellomere 490 µm long; AR 1.58. Length of palpomeres (I–V) (µm): 23: 46: 92: 105: 149. CA 0.63–0.68.

Thorax. Acrostichals 4, dorsocentrals 12–14, prealars 3, supraalars 1–2 and scutellars 6–8.

Wing ( Fig. 3A ). VR 1.14. R with 17 setae, R 4+5 with 18 setae. Brachiolum with 2 setae. Squama with 4 fringed setae. FCu distinctly distal to RM. Anal lobe moderately developed.

Legs. Fore tibia with 2–3 setae. Mid legs with 2 tibial spurs; 16–18.4 and 20.7 µm long, comb with 36–40 teeth. Hind leg with 2 tibial spurs; 23 µm and 25.3 µm long, comb with 48–50 teeth. Lengths (µm) and proportions of legs shown in table 2.

Hypopygium ( Figs. 3B–D ).Anal tergite band Y shaped.Anal point 76–80.5 µm long, 9.2–11.5 µm wide, slightly widened sub apically, apically rounded, bearing 3–4 lateral setae on each side. Transverse sternapodeme 23–30 µm long. Digitiform superior volsella 18.34–20.7 µm long, 6.9–9.2 µm wide ( Fig. 3D ), partially bifurcated apex bearing 2 setae. Inferior volsella absent. Gonocoxite 138 µm long. Gonostylus 156–166 µm long, widest medially, apically pointed and strongly curved in middle with strong longitudinal keel. HR 0.84–0.88; HV 2.17.

Distribution ( Fig. 4 ). West Bengal, India (present record).

Remarks. The new species shows closeness with D. (I). concavus Yan, Tang et Wang, 2005 in having somewhat similar shaped gonostylus but differs in the shape of superior volsella. Small thumb–like superior volsella is possessed by the new species and D. (I). fastigatus ( Townes, 1945) , but superior volsella is apically bisected in the new species while it is undivided apically in the latter species.

Figures

FIGURES 3. Adult male Demicryptochironomus (Irmakia) dividuus sp. n. A. wing, B. hypopygium, C. hypopygium scale 0.01 mm, D. superior volsella scale 0.01 mm.

FIGURE 4. Distribution map of Demicryptochironomus (Irmakia) dividuus sp. n.