Robackia aequilongia, Mukherjee & Hazra, 2022

Mukherjee, Bindarika & Hazra, Niladri, 2022, First records of three genera, Cyphomella Saether, 1977, Olecryptotendipes Zorina, 2007 and Robackia Saether, 1977 of the Harnischia complex from India with description of O. extentus sp. n., O. obtunsus sp. n. and R. aequilongia sp. n. (Diptera: Chironomidae), Zootaxa 5091 (2), pp. 330-340 : 331-333

Robackia aequilongia sp. n.

GenBank Accession no. MZ298127

LSIDurn:lsid:zoobank.org:act: D58B3BF0-FD16-4029-8C15-EA1839B3722A

Material examined. Holotype male, labelled ‘ Holotype Robackia aequilongia sp. n., India, West Bengal, Purulia [23.1481° N, 86.5451° E], 08.iii.2020, Coll. T. Mukherjee’ . Paratype 1 male, labelled ‘ Paratype Robackia aequilongia sp. n., India, West Bengal, Burdwan [23°22ʹN, 87°85ʹE], 15.vi.2020, Coll. N. Hazra’ .

Diagnostic characters. The adult male is distinguished from other species of the genus Robackia by the presence of a distally bilobed superior volsella, rounded posterior ventral margin of tergite IX and absence of strong setae on tergite IX.

Etymology. The name ‘ aequilongia ’, a Latin word, derived from ‘ aequilongi ’, refers to bilobed superior volsella.

Male (n=2)

Total length 3.7 mm. Wing length 1.9–1.93 mm. Costal length 1.81–1.85 mm. Antennal length 0.94–0.97 mm.

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

Head. Head width 510–530, 520 µm. Temporal setae 8–10 (IV 2–3, OV 4–5, Po 2). Clypeal setae 12. Frontal tubercle absent. Eyes bare with dorsomedial extension of 120–130 µm. Ultimate flagellomere 630–660 µm long; AR 2.03–2.13. Length of palpomeres (I–V) (µm): 20: 40: 90: 100: 160. CA 0.53–0.56, 0.54.

Thorax. Antepronotum notched, scutal tubercle absent, antepronotal 0, dorsocentrals 8, scutellars 4. Others not countable.

Wing ( Fig.1A ). VR 1.05. R with 1 seta, R 1 and R 4+5 bare. Brachiolum with 2 setae. Squama with 13 fringed setae. Anal lobe well developed.

Legs. Fore tibia with 1–2 setae. Mid legs with 2 tibial spurs; 23.6–25.3 µm and 23 µm long with 28–30 teeth. Hind leg with 2 tibial spurs; 27.6–29.9 µm and 16.1–18.4 µm long with 42–44 teeth. Lengths (µm) and proportions of leg segments shown in table 1.

Abdomen. Tergite IX with numerous ventral setae. Rounded posterior ventral margin of tergite IX and absence of strong setae on tergite IX.

Hypopygium ( Figs. 1B–E ). Anal tergite band V shaped. Anal point parallel sided, distally rounded; 43.7–46 µm long, 11.5 µm wide. Anal point bearing 3–4 lateral setae on each side. Transverse sternapodeme 34.5–36.8 µm long. Superior volsella ( Fig. 1D ) bilobed, subequal in size; inner part rod like, 50.6 µm long with 1 apical and 1 subapical setae arising from strong base and outer part bare, apically little swollen, 55.2–57.5 µm long, 6.9–9.2 µm wide at base and 13.8 µm wide at apex. Inferior volsella small, disc like, microtrichiose. Gonocoxite 144.9–149.5 µm long. Gonostylus 169.7–172.5 µm long. HR 0.85–0.87; HV 2.47–2.51.

Distribution. West Bengal, India (present record).

Remarks. The new species is closely related to R. parallela Yan et Wang, 2006 , in having more or less similar LR, equal number of dorsocentrals and parallel-sided anal point but differs in the shape of superior volsella (digitiform in C. parallela while it is bilobed in the new species), number of setae on anal point (12 weak setae in C. parallela while 6 weak setae in new one), squamal setae (5 in C. parallela while 13 in new one) and R vein (3 in C. parallela while 1 in new one). Robackia pilicauda Saether, 1977 has a distally swollen superior volsella and nearly parallel-sided anal point, but the combination of characters such as the presence of setae on the inner part of bilobed superior volsella, absence of strong setae on tergite IX, reduced number of seta(e) on R vein and numerous setae on squama can easily distinguish the new species from R. pilicauda .

Figures

FIGURES 1A–E. Adult male Robackia aequilongia sp. n. A. Wing, B. Hypopygium (dorsal), C. Hypopygium (ventral), D. Superior volsella, scale 0.01 mm, E. Hypopygium, scale 0.01 mm.