Corethrella (Corethrella) nanoantennalis 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 : 9-10

Corethrella (Corethrella) nanoantennalis Borkent & Grafe , new species

( Figs. 3 A, 4C, 6C, 8C, 9C, 12C, 13C, 14A)

DIAGNOSIS: Male adult. Unknown. Female adult. Only extant species of Corethrella in the Palaearctic, Oriental, Oceanian and northern Australasian Regions with the combination of no pigmentation distal to a single distinct midlength wing band (no subapical band) ( Fig. 12C ), flagellomeres 1–4 short, each notably shorter than flagellomere 5 ( Fig. 8 C), with non-discrete darker pigmentation on the basal 0.5 of the midfemur and basal 0.3–0.4 of the hind femur, uniformly yellow or light brown hind tibia, and abdominal tergites each with an anterior darker band ( Fig. 9C ). Only extant species in Borneo with the combination of flagellomeres 1–4 short ( Fig. 8 C) and palpal segments 1–2 dark brown and contrasting with pale segments 3–4 (5 grading from pale to medium brown) ( Fig. 6 C).

DESCRIPTION: Male adult. Unknown. Female adult. Descriptive statistics: See Tables 1 –5. Head: Outline in anterior view somewhat circular ( Fig. 6 C). Coronal suture elongate, extending ventrally past ommatidia. Two large setae on frons between ventromedial area of ommatidia. Antenna uniformly medium brown; pedicel without distinctive elongate, stout setae. Antennal flagellomeres as in Fig. 8 C; sensilla coeloconica on flagellomeres 1–2, 9–13, only flagellomere 1 with more than one; flagellomere 13 with well-developed apical bifurcation. Clypeus ( Fig. 6 C) somewhat square. Mandible with very small, pointed teeth. Palpus ( Fig. 6 C) with segments 1–2 dark brown, very base of segment 3 dark brown or pale, most or all of segment 3, segments 4 light brown, segment 5 grading from light to medium brown apically; segment 3 swollen apically. Thorax ( Fig. 9C ): Scutum, scutellum mostly light to medium brown, contrasting with darker brown pleura; 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, uninterrupted, extending to near 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 not thick. Wing ( Fig. 12C ): Apex of R2 slightly distal to apex of M1. Anterior margin with differently, discretely pigmented scales (indicating anterior margin of midlength band), with midlength band, with darker more basal scales restricted to vein C, Sc, slightly in more posterior veins, with basal scales on posterior margin of wing dark; veins (other than costa and wing margin) with well-developed scales. Halter medium brown, equal to scutellum. Legs ( Fig. 9C ): Light brown, with about basal 0.5 of forefemur slightly darker, about basal 0.5 of midfemur darker, about basal 0.2–0.3 of hind femur darker; with darker pigmentation not discrete. 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 thick. Abdomen ( Fig. 13C ): Tergites 2–7 pale with anterolateral corners more darkly pigmented, sternites light brown with sternites 2–6 with posterior margin pale. Segments 8–9 medium brown. Cercus pale.

Immature stages. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella nanoantennalis is known from female specimens collected in Ulu Temburong National Park in Brunei at 110 m and Lanjak Entimau, Sarawak, Malaysia at 80 m ( Fig. 14A ). Habitats are found in steep terrain in mature mixed dipterocarp forest (as in Fig. 1 F). One female was collected with a frog-call trap broadcasting 4 kHz, the maximum frequency (Hz) attractive to any Corethrella species (Grafe et al. unpublished). The others were collected feeding on calling males of two species of frogs (Table 7).

TAXONOMIC DISCUSSION: We have placed C. nanoantennalis in the drakensbergensis species group based on the presence of synapomorphies 21–23 and its plesiomorphic complete prescutal suture (character 28) ( Fig. 19 ). It could equally form an earlier lineage anywhere between the nodes defined by Borkent (2008: fig. 141) by "21–23" and "26, 28–30". Discovery of the male will help resolve its phylogenetic position.

TYPES: Holotype, female adult on microscope slide, labeled " HOLOTYPE Corethrella nanoantennalis Borkent and Grafe ", "Sungai Mata Ikan, Ulu Temburong National Park, Brunei, 10-VII-2008; on M. nasuta, U. Grafe ; 11n1", "11n1 050109 " (CNCI). Paratypes on microscope slides: 4 Ƥ, Lanjak Entimau, Sarawak, Malaysia, 112° 4'E, 1° 28'N, 80 m, 24-VI-2008 (CNCI); 1 Ƥ, from previous locality but 18-VI-2008 (UBD). Paratypes on pins: 11 Ƥ, Lanjak Entimau, Sarawak, Malaysia, 112° 4'E, 1° 28'N, 80 m, 24-VI-2008 (9, CNCI; 2 UBD); 1 Ƥ, from previous locality but 18-VI-2008 (CNCI).

DERIVATION OF SPECIFIC EPITHET: The name nanoantennalis (small, antenna) refers to the relatively short flagellomeres 1–3 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 3. Female adult Corethrella feeding on calling male frogs in Borneo. A. C. nanoantennalis on thorax and legs of Ansonia longidigita (Inger) (Lanjak Entimau, Sarawak, Malaysia; photograph by second author). B. C. mitra on area surrounding nares of Limnonectes leporinus (Andersson) (30 km NE Kalabakan, Sabah, Malaysia; photograph by Oliver Konopik; note reddish abdomens of engorged females).

FIGURE 6. Head capsules of female Corethrella, anterior view.

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 19. Phylogenetic relationships of Corethrella from Borneo to other species and showing their distributions. Numbers refer to character states given in Borkent (2008). Evidence for cladistic relationships given in Borkent (2008).

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

FIGURE 9. A – D. Thoraces and legs of female Corethrella, lateral view; slide-mounted.

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

FIGURE 14. A – B. Distributions of species of Corethrella from Borneo.