Compteromesa biramosa Tang et Niitsuma, 2021

Shi, Jianyu, Niitsuma, Hiromi & Tang, Hongqu, 2021, Compteromesa Sӕther (Diptera, Chironomidae, Prodiamesinae) newly recorded in China with the description of a new species, Zootaxa 5082 (2), pp. 169-176 : 174-176

Compteromesa biramosa Tang et Niitsuma , sp. n.

( Figure 4 ) http://zoobank.org/ urn:lsid:zoobank.org:act:BA335A9F-D189-427D-A76B-C650ECCC0B5E

Type material. Holotype, M ( EJNU), CHINA: Yunnan Province, Xishuangbanna Prefecture, Mengla County, Bubang country, Xishuangbanna Tropical Rainforest National Park , Wangtianshu Scenic Area , 21°37′26.88″N, 101°35′18.43″E, alt. 730 m, 25.iv.2017, H.Q. Tang and J. Chen.

Etymology. From Latin biramosus (biramous), referring to the gonostylus.

Description. Male (n = 1). Total length 4.0 mm, wing length 2.2 mm.

Coloration. Body predominantly yellowish brown; thorax brown on episternum, epimeron, scutellum and postnotum, with deep yellow scutal vittae; brown pigments present around humeral pit. T II–VII each with distinctly brown band on anterior 1/10–1/5; T VIII and hypopygium brown.

Head. Eyes bare; dorsomedial extensions short, triangular, separated by twice length of extension. Terminal flagellomere 560 μm long; AR 1.04. Lengths of palpomeres 1–5 (μm): 25, 25, 90, 90, 140. Temporals 12, forming line close to dorsal margin of eye. Clypeus with 25 setae.

Thorax ( Fig. 4A ). Scutum remarkedly projected over antepronotum, incision between apices of scutum and antepronotum deep in lateral view. Humeral pit ( Fig. 4B ) elongated, 60 μm long, 20 μm wide, consisting of many small pits. Antepronotals 5; dorsocentrals 12, uniserial in anterior half and biserial in posterior half; supraalrs absent; prealars 3. Scutellum with 22 setae.

Wing ( Fig. 4C ). Membrane without setae, anal lobe slightly developed. R with 19 setae, R 1 with 17 setae and R 4+5 bare. VR 1.10. Squama with 5–6 setae. Distance along M from RM to FCu 50 μm; RM 80 μm long, and MCu 100 μm long. Costal extension 70 μm long.

Legs. Foretibia with one spur, 45 μm long; mid tibia with 2 spurs subequal, 50–55 μm long; hind tibia with 2 spurs, 50 μm and 70 μm long, respectively. These spurs with side teeth appressed tightly to shaft. Hind tibial comb with 6–7 spiniform bristles. All tarsi without pseudospurs. Pulvilli reduced. LR 1 0.84, LR 2 0.55, LR 3 0.58; BV 1 2.36, BV 2 3.53, BV 3 3.14; SV 1 2.21, SV 2 3.67, SV 3 3.21; BR 1 2.33, BR 2 2.29, BR 3 2.67.

Hypopygium ( Figs 4D, E ). T IX with 8–10 setae on each posterolateral portion. Anal point semicircular, entirely covered with microtrichiae. Gonocoxite 310 μm long. Superior volsella absent. Inferior volsella small, with many strong setae arising from tubercles. Median volsella reduced to swelling covered with relatively long microtrichiae, with long apodeme and basal transverse bar. Gonostylus bilobed; inner lobe plate-like, almost 0.7 times as long as outer lobe; megaseta ( Fig. 4F ) simple, 10 μm long, shorter than distal thickness of gonostylus. HR 2.1.

Remarks. The male resembles those of Compteromesa oconeensis and C. haradensis in the thoracic humeral pit consisting of small pits and the hypopygium with small inferior volsellae, and median volsellae reduced to apodemes, but differs from them in the eye with a short and wedge-shaped dorsomedial extension, the wing membrane without setae, the semicircular anal point and the bilobed gonostylus with a simple, short megaseta in the hypopygium. In the latter two species, the male has eyes with long and parallel-sided dorsomedial extensions, wing membrane with setae, an elongated anal point and simple gonostyli with a slender, slightly sinuate and longer megaseta ( Saether 1981, Niitsuma & Makarchenko 1997). Further, the male is characterized by the completely reduced superior volsellae in the hypopygium, too. It is unique in the subfamily Prodiamesinae , since usually the males of the subfamily have more or less developed superior volsellae ( Saether 1989). Therefore, the status of this species in this subfamily is tentative, which will be confidently assigned into the accurate generic status when the immature stages are available to us.

Figures

FIGURE 4. Compteromesa biramosa Tang et Niitsuma sp. n., male. A–B, Thorax, lateral view; C, wing; D, hypopygium, dorsal view; E, hypopygium, ventral view; F, apex of gonostylus with megaseta.