Dasyhelea (Dasyhelea) trigona, Brahma & Chatterjee & Hazra, 2023

Brahma, Shubhranil, Chatterjee, Somnath & Hazra, Niladri, 2023, Five new Indian species of the genus Dasyhelea Kieffer (Diptera, Ceratopogonidae) with a key to the adult males, Evolutionary Systematics 7 (1), pp. 51-66 : 51

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Dasyhelea (Dasyhelea) trigona

sp. nov.

Dasyhelea (Dasyhelea) trigona sp. nov.

Type material.

Holotype ♂, India, West Bengal, Birbhum, Boidhora [24°14'59.4"N, 87°44'20.2"E], 25.XII.2016, Coll. S. Chatterjee. Paratype: 1♂, India, West Bengal, South 24 Parganas, Bali Island [22°05'19.6"N, 88°45'25.7"E], 15.V.2017, Coll. S. Brahma.


The only species in the subgenus Dasyhelea Dasyhelea having tubercles on the frontal sclerite, femora with infuscation beyond the mid region and an aedeagus with ventral triangular basal arms.


Male adult (n = 2) (Figs 5A-K View Figure 5 , 8C View Figure 8 ). Total body length 2-2.1 mm.

Head. Dark brown in colour. Eyes separated by half of diameter of ommatidium. Frontal sclerite (Fig. 5A View Figure 5 ) 57.5 μm long, 55 μm wide, with oval base, small dome shaped apical portion ending in a threadlike projection and base containing sclerotised tubercles. Antennal flagellum (Fig. 5B View Figure 5 ) brown, 0.9 mm long; flagellomere XIII with a distinct apical projection; length ratio of flagellomeres (I-XIII): 17: 14: 11.5-12: 12: 15-15.5: 14-14.5: 14: 15: 15: 29-29.5: 23.5-24: 20: 38.5-39; AR 1.00; flagellomeres III-XIII (visible) with sensilla basiconica. Clypeus (Fig. 5C View Figure 5 ) with 4 pairs of setae. Palpus (Fig. 5D View Figure 5 ) pale brown; length ratio of palp segments (I-V): 6: 10-10.5: 13: 11-11.5: 14; PR 2.16; palp segment III with 6 capitate sensilla at proximal half.

Thorax (Fig. 5E View Figure 5 ). Brown in colour without any prominent infuscation. Acrostichals 11-12 pairs, biserial; dorsocentrals 10-11 pairs, biserial and 7, uniserial; 13 prealars; scutellum with 6 setae.

Wing (Fig. 5F View Figure 5 ). Wing margin with short, prominent macrotrichia; anterior margin of r5 with microtrichia. WL 0.95-1.00 mm, WW 0.35 mm, CR 0.5. Cubital fork lying well before costal extremity.

Legs (Fig. 5G View Figure 5 ). Pale brown in colour. Femora infuscated at mid region, mid tibia with diffused infuscation, proximads of tibiae dark brown. Hind tibial comb (Fig. 5H View Figure 5 ) with 7 spines, third one from inner longest. TRI 3.14-3.18, TRII 3.14 and TRIII 2.94.

Abdomen. Brown in colour.

Genitalia (Figs 5I View Figure 5 , 8C View Figure 8 ). Tergite 9 broad apically, 100.5-101 μm long and 172-173 μm wide. Apicolateral processes (Fig. 5J View Figure 5 ) short with basal notch, 11-12 μm long, with one prominent apical seta, cercus with three setae. Sternite 9 2 × wider than length, with convex margin. Gonocoxite stout, elongated, 78 μm long, greatest width 46-57.5 μm, having 3-4 setae dorsally. Gonostylus stout, long, gradually tapering, 92-94 μm in length, 23-30 μm wide basally, 9 μm wide subapically, 7-8 μm wide apically; 2 long setae present at about proximal one fourth and one third length dorsally and 1 long seta at about proximal one third, all directed outwardly; one prominent, seta from about half distance from base, directed inward, 2 prominent setae subapically and 2 at apex. Left basal arm of parameres (Fig. 5I View Figure 5 ) 103.5 μm long, and right basal arm 90-92 μm long, both thin, highly sclerotised, joined broadly with 92 μm long, 16-18.5 μm wide, moderately sclerotised, and pointed tipped posteromedian projection of parameres terminating at level of gonocoxite-gonostylus junction. Aedeagus (Fig. 5K View Figure 5 ) broad, 50.5-57.5 μm long, 94-99 μm wide, basal arm 18.5-19 μm long, highly sclerotised, directed slightly posterolaterad, ending in triangular projection ventrally, basal arch 32-44 μm long, posterolateral arm 34.5-39 μm long, stout, ending in point; bifurcated, tubular ventromedian projection.

Female adult. Unknown.

Pupa and Larva. Unknown.


The name " Dasyhelea trigona " derived from Latinised version of triangle, referring to triangular ventral region of the basal arm of the aedeagus of male genitalia.


The new species Dasyhelea (D.) trigona bears similarities with D. (D.) fulcillata Yu in Yu et al. 2005 (China) in the shape of the gonocoxite and basal arms of the parameres, but differs in the apicolateral process, absence of setae at the basal half of gonostylus, and the overall structure of the parameres and the aedeagus. It is also close to Dasyhelea (D.) abdita Yu in Yu et al. 2005 (China) in the structures of parameres and aedeagus, but the basal arm of aedeagus, the apicolateral process and the apex of gonostylus are different. The present species owes resemblances with D. (D.) actita Yu in Yu et al. 2005 (Taiwan) in the structure of the posterolateral arms of the aedeagus and the basal arms of the parameres, but the overall structure of parameres and apicolateral processes are dissimilar. The new species and D. (D.) ampullariae Macfie, 1934 (Malaysia, and China) look alike in parameres but the structure of the gonostylus, the apicolateral process and the aedeagus disagree. The combination of characters provided in the diagnosis validates D. (D.) trigona as a new member of this subgenus.


The materials were collected from the Deltaic Proper of Gangetic of West Bengal at an altitude of 6-60 meters above sea level - new species from India.

Ecological notes.

Adults of Dasyhelea (D.) trigona sp. nov. were trapped around a paddy field adjoining a freshwater river (Fig. 2C View Figure 2 ); the air temperature and relative humidity were 15-17 °C and 70-75% respectively.

Subgenus Dasyhelea Sebessia Remm, 1979