Corethrella (Corethrella) bicincta Borkent, Grafe

Borkent, Art & Grafe, Ulmar, 2012, The Frog-Biting Midges of Borneo — From Two to Eleven Species (Corethrellidae: Diptera), Zootaxa 3279, pp. 1-45 : 16-17

Corethrella (Corethrella) bicincta Borkent, Grafe & Miyagi, new species

( Figs. 5 D, 7C, 8J, 11A, 12J, 13I, 15B)

DIAGNOSIS: Male adult. Unknown. Female adult. Only extant species of Corethrella in the Palaearctic, Oriental, Oceanian and northern Australasian Regions with the combination of a subapical band on the wing ( Fig. 12J ), a uniformly brown abdomen ( Fig. 13I ), and with the hind tibia with darker pigmentation at base and apex ( Fig. 11A ). Only extant species in Borneo with the combination of a subapical band on the wing ( Fig. 12J ) and a uniformly brown abdomen ( Fig. 13I ).

DESCRIPTION: Male adult. Unknown. Female adult. Descriptive statistics: See Tables 6 –11. Head: Outline in anterior view laterally somewhat elongate ( Fig. 7C ). Coronal suture elongate, extending to midheight to ventrally past ommatidia. Two large setae on frons between ventromedial area of ommatidia. Antenna uniformly medium brown; pedicel with distinctive, more elongate, stout, dorsal or dorsolateral setae; flagellomeres as in Fig. 8 J; sensilla coeloconica on flagellomeres 1, (8), 9–13, flagellomeres 1 with several, 9–13 with 2 sensilla; flagellomere 13 with well-developed apical bifurcation. Clypeus ( Fig. 7C ) wide. Mandible with moderately small, pointed teeth. Palpus ( Fig. 7C ) brown; segment 3 swollen subapically. Thorax ( Fig. 11A ): Uniformly medium to dark brown but scutum with anterolateral darker patch of darker pigmentation, pale sclerites around base of wing. Posterior portion of dorsocentral row with 2 elongate setae situated somewhat lateral to one another. Prescutal suture elongate, thick, interrupted by area of pale cuticle, extending nearly to dorsocentral row of setae. Anterior anepisternum divided diagonally by sinuous suture, dorsal portion about equal to ventral portion. Ventral portion of posterior anepisternum triangular, uniformly brown, with anterodorsal margin thick. Wing ( Fig. 12J ): Apex of R2 equal to apex of M1. Anterior margin with differently, discretely pigmented scales (indicating anterior margin of wing bands), basal band with dark scales on C, Sc, R, subbasal band with dark scales on R, M, A1, midlength band entire, subapical band with dark scales but R4+5 pale; veins (other than costa and wing margin) with well-developed scales. Halter as dark as scutellum. Legs ( Fig. 11A ): Uniformly pigmented dark brown, except for poorly defined lighter pigmentation on apex of forefemur, base of foretibiae in some, in all apical 0.3 of hind femur pale, hind tibiae pale but with basal and apical bands of dark pigmentation. With only slender setae, lacking scales. Midleg with thick, subapical setae on each of at least tarsomeres 1–3. Claws of each leg equal to those of others; equal on each leg, simple (without inner teeth). Empodia slender. Abdomen ( Fig. 13I ): Uniformly medium brown, with segments 8–9. Cercus darker brown.

Immature stages. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella bicincta is known from Brunei and eastern Sarawak, Malaysia ( Fig. 15B ) at elevations of 30–1083 m. Habitats include mid-elevation peat swamps or a nearby river ( Fig. 1 G) and steep terrain in lowland mature mixed dipterocarp forest. They were collected with frog-call traps and on a calling male of one species of frog (Table 7).

TAXONOMIC DISCUSSION: The specimens from Brunei and Gunung Mulu National Park (low elevations) were smaller (wing length less than 1.3 mm) than those from the Bario highlands (wing length more than 1.4 mm). Corethrella bicincta may be the first Old World species of the quadrivittatus species group. It has all the synapomorphies of the lineage identified by characters 39–44 ( Borkent 2008: fig. 141) although character 44 could not be scored (present only in the currently unknown male). Corethrella bicincta lacks, however, both the apomorphic state of characters 33 and 68 and must be considered as unplaced until other life stages and character states become available.

TYPES: Holotype, female adult on microscope slide, labeled " HOLOTYPE Corethrella bicincta Borkent, Grafe and Miyagi", "Gunung Mulu National Park, Sarawak, Malaysia, Headquarters, 14-XI-2009; on Hylarana glandulosa, U. Grafe ;" (CNCI). Paratypes on microscope slides: 1 Ƥ, labeled as for holotype (CNCI); 10 Ƥ, Bario, Sarawak, Malaysia, 1060 m, on several dates: 2-VIII-2007, 6,7-IX-2007, 29-VIII-2008 (9, CNCI; 1, UBD). Paratypes on pins: 1 Ƥ, Pa Umor, 5 km E. Bario, Sarawak, Malaysia, 1083 m, 25-XI-2010 (CNCI); 1 Ƥ, 0.5 km E Pa Umor, 03°44' N 115°30'E, Sarawak, Malaysia, 1083 m, 27-XI-2010 (CNCI); 11 Ƥ, Sungai Ingei, 8.2 km S. Melilas, Brunei, 50 m, VII-2010 (10, CNCI; 1 UBD); 12 Ƥ, from previous locality but 10-VII-2010 (11, CNCI; 1 UBD); 5 Ƥ, Gunung Mulu National Park, Sarawak, Malaysia, Headquarters, 30 m, 14-XI-2009 (CNCI).

DERIVATION OF SPECIFIC EPITHET: The name bicincta (two belts) refers to the presence of both a midlength and subapical band on the wing of females of this species.

Figures

FIGURE 1. Habitats from which Corethrella adults were collected with a frog-call trap in Brunei (species collected given in parentheses). A. 12 km S. Liang, Brunei (C. tigrina, C. lutea, C. calathicola, C. pauciseta, C. gilva) (authors, for scale). B. Nepenthes ampullaria, 12 km S. Liang, Brunei (C. calathicola). C. 12.5 km S. Liang, Brunei (same species as for A) (first author, for scale). D. 20 km N. Labi, Luagan Lalak Forestry Rec. Site, Brunei (C. lutea). E. Belalong River, Kuala Belalong Field Studies Centre, Brunei (C. lutea, C. bipigmenta, C. mitra). F. Sungai Esu, Ulu Temburong NP, Brunei (C. tigrina, C. bipigmenta, C. mitra) (first author's wife Annette, for scale). G. Pa Umor, 5 km E. Bario (C. bicincta, C. unizona).

FIGURE 5. Habitus of adult female Corethrella, in lateral view, all in alcohol.

FIGURE 8. Antennae and male genitalia of Corethrella. A – K. Antennae of female Corethrella. L. Antenna of male C. tigrina. M. Male genitalia of C. tigrina, dorsal view; parts drawn in proportion to each other.

FIGURE 12. A – K. Wings of female Corethrella.

FIGURE 13. A – J. Abdomens of female Corethrella, ventral view.

FIGURE 11. A – B. Thoraces and legs of female Corethrella, lateral view; slide-mounted. C. Portion of midfemur of female C. calathicola, at about distal third of femur, showing scales, dorsal view (with leg extended laterally from body).

FIGURE 7. A – D. Head capsules of female Corethrella, anterior view. E – H. Antennal flagellomeres 1 – 4 of female.

FIGURE 15. A – B. Distributions of species of Corethrella from Borneo.