Diamesa aculeata, Willassen, Endre, 2005

Willassen, Endre, 2005, New species of Diamesa (Diptera: Chironomidae) from Tibet: conspecific males and females associated with mitochondrial DNA, Zootaxa 1049, pp. 19-32 : 25-26

Diamesa aculeata new species

( Figs. 2A–E )

Holotype male: China: Tibet, Rongbuk, 5000 m a.sl., 7.Jul. 1993, leg. T. Solhøy, det. E.Willassen, EW36. In Academica Sinica, Zoological Institute, Beijing.

Etymology: The species name is from Latin aculeatus, sharp­pointed, referring to the cuspidate microtrichia on the mesal edge of the male gonocoxite.

Genetics: Genbank accession number AM 051233 , mitochondrial COII gene for cytochrome oxidase subunit II.

Male imago (n = 1)

Head: Antenna plumose with 13 flagellomeres; longest antennal seta longer than ultimate flagellomere; AR 1.2; pedicel large, with 3 setae. Eyes moderately projecting dorsomesally; with pubescence between ommatidia. Coronal suture complete. Temporal setae including 3 orbitals, 17 verticals, and 9? postorbitals. Clypeus 130 m long, 107 m wide; with 12 setae. Palpomere lengths (m): 37, 85, 133, 126, 211. Tentorium with conspicuous anterolateral projection.

Thorax damaged in DNA preparation.

Wing: Length 3.17 mm. VR 0.88. Membrane without setae, punctuation of microtrichia distinct at 100x magnification. Costa produced beyond R4+5. R with 15 setae, R1 with 12 setae and 2 sensillae campaniformia, R2+3 with 2 sensillae campaniformia, R4+5 with 3 setae and 1 sensilla campaniformia. Alula without setae. Squama with marginal fringe of about 35 setae.

Legs: Comb on ti3 with 15 setae. Tarsi 1–3 respectively with following numbers of apical/preapical pseudospurs: 2/0, 2/0, ­/­ on p1; 2/7, 2/5, 2/0 on p2; 2/10, 2/5, 2/0 on p3. Hind leg with about 25 sensillae chaetica distributed from 0.45 to 0.52 of ta1.

Hypopygium: Sternapodeme arced. Pars ventralis moderately large ( Fig. 2B ); with longitudinal striae, but without microtrichia. Aedeagal lobes sickle­shaped, mesal margin well sclerotised. Basal plate of gonocoxite weakly developed. Basimedial setal cluster absent. Medial field almost completely devoid of microtrichia dorsally; dorsal edge of mesal margin ( Fig.2A ) with ornamentation of thornlike microtrichia that are particularly dense on the ventral side ( Fig.2C ); ventromesal margin of gonocoxite with setae and weak microtrichia ( Fig. 2B ) Gonostyli somewhat flattened and twisted, apex with sclerotised point and 1 megaseta. Tergite IX divided into 2 oval protrusions, each with about 15 moderately long setae. Tergal bands relatively distinct, running from anterior margin of tergite IX to the free base of anal point. Anal point inserted between tergal protrusions; base broad with microtrichia; distal part slender and nude, apex slightly expanded with 1 distal peg­sensilla ( Fig. 2D ).

Female imago (n = 1, putative association)

Head: Antennae partly lost. Pedicel with 5 or 6 setae. Coronal suture complete. Temporal setae more or less contiguous, about 40 on each side, including 9 postorbitals. Eyes pubescent, moderately projecting dorsomesally. Clypeus 167 m long, 152 m wide, with 24 setae. Palps lost. Tentorium with conspicuous anterolateral projection.

Thorax: Antepronotum with 9 lateral setae. Acrostichals absent. Dorsocentrals 16 in 1 row, except anteriorly; 9 prealars behind callus, and about setae on 40 scutellum. Protuberance of epimeron II with 8 setae.

Wing: Length 4.11 mm. VR 0.91. Punctuation of membrane visible at 125x magnification. Costa well produced beyond R4+5. R with 18 setae. R1 with 19 setae and 2 sensillae campaniformia. R2+3 with 2 sensillae campaniformia. R4+5 with 18 setae and 3 sensillae campaniformia. Alula with 5 setae. Squama with marginal fringe of about 60 setae.

Legs: Lost except right hind femur and tibia. Comb of hind tibia with 15 setae.

Genitalia ( Fig. 2E ): Sternite VIII with about 20 short setae on each side. Gonocoxapodeme conspicuous with distinct anteromesal curve. Gonapophysis VIII with flap covering mesal part of ventolateral lobe. Seminal capsules elongate with long neck, capsule surface with weak granulation. Seminal ducts with few bends. Gonocoxite IX with laterally directed knoblike projection; about 15 weak setae confined to knob. Tergite IX completely divided into 2 plates, of which broader lateral parts are slightly more sclerotised; each plate with about 20 relatively short setae. Segment X slightly protruding laterad. Cerci rounded in lateral view.

Remarks: The male of D. aculeata is superficially similar to Diamesa bertrami Edwards and also to the Himalayan Diamesa kasaulica Pagast described by Serra­Tosio (1983). The ornamentation of the mesal edge and otherwise smooth medial field may serve as diagnostic features of male D. aculeata . Both D. bertrami and D. kasaulica have hairy eyes as opposed to the weakly pubescent eyes in D. aculeata . The only female specimen with pubescent eyes in the Rongbuk material presumably also belongs to D. aculeata . Antennae, palps, and most of the legs are lacking and the wings were preserved in a folded state. A short, partial Cox II sequence was recovered from the male of D. aculeata , but sequences were not obtained from the putative female.

Additional material: China: Tibet, Rongbuk, 5000 m a.sl., 9.Jul. 1993, Malaise Trap, leg. T. Solhøy, det. E. Willassen; 1 female ( IZAS).

Figures

FIGURES 2 A – E. Diamesa aculeata new species. A, male genitalia in dorsal view. B, ventral view of pars ventralis, aedeagal lobe, basal plate and ventromesal margin of gonocoxite IX. C, ventral view of cuspidate microtrichia along dorsomesal edge of medial field. D, apex of anal point. E, female genitalia in lateral view.