Corethrella (Corethrella) gilva 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 : 17-18

Corethrella (Corethrella) gilva Borkent & Grafe , new species

( Figs. 5 E, 7D, 8K, 11B, 12K, 13J, 16A)

DIAGNOSIS: Male adult. Unknown. Female adult. Only extant species of Corethrella in the Palaearctic, Oriental, Oceanian and northern Australasian Regions with the combination of the palpus and clypeus equally dark brown ( Fig. 7D ), a single, midlength wing band ( Fig. 12K ), tergites 2–6 uniformly brown ( Fig. 13J ), midfemur either uniformly brown or lighter apically (non-discrete), and hind tibia with, at most, very light pigmentation at apex ( Fig. 11B ). Only extant species in Borneo with the combination of the palpus and clypeus equally dark brown ( Fig. 7D ), a single, midlength wing band ( Fig. 12K ), hind tibia with, at most, very light pigmentation at apex ( Fig. 11B ), and tergites 2–6 uniformly brown ( Fig. 13J ).

DESCRIPTION: Male adult. Unknown. Female adult. Descriptive statistics: See Tables 1 –5. Head: Outline in anterior view somewhat circular ( Fig. 7D ). Coronal suture elongate, extending ventrally nearly past ommatidia. Two large setae on frons between ventromedial area of ommatidia. Antenna uniformly medium brown; pedicel with distinctive elongate, stout setae. Antennal flagellomeres as in Fig. 8 K; sensilla coeloconica on flagellomeres 1–2, 8–13, only flagellomere 1 with more than one; flagellomere 13 with well-developed apical bifurcation. Clypeus ( Fig. 7D ) somewhat square. Mandible with very small, pointed teeth. Palpus ( Fig. 7D ) medium brown; segment 3 swollen near midlength. Thorax ( Fig. 11B ): 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. 12K ): Apex of R2 equal or slightly distal to apex of M1. Anterior margin with differently, discretely pigmented scales (indicating anterior margin of midlength band), with midlength band, with poorly defined basal band; veins (other than costa and wing margin) with well-developed scales. Halter medium brown, equal to scutellum. Legs ( Fig. 11B ): Medium brown, with about apical 0.3 of midfemur, basal 0.5 of midtibia, apical 0.5 of hind femur, all of hind tibia pale other than slightly darker pigmentation on apical 0.2 of hind tibia; 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. 13J ): Tergites 1–6 pale, sternites 1–6 light brown, segments 7–9 medium brown. Cercus medium brown.

Immature stages. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella gilva is known from Brunei at 30–110 m ( Fig. 16A ). Habitats include lowland peat swamps (including standing water and very slow moving streams) and steep terrain in mature mixed dipterocarp forest ( Fig. 1 A, as in Fig. 1 F). Females have been collected with frog-call traps and on calling males of three species of frogs (Table 7).

TAXONOMIC DISCUSSION: Borkent (2008: 237) noted three species attracted to the taped call of Hyla gratiosa (LeConte) in Brunei and C. gilva was one of them (included as a paratype here).

We are uncertain of the phylogenetic placement of C. gilva because it is known only as female adults and there were few synapomorphies present to interpret. Corethrella gilva has synapomorphies 21–23 and lacks synapomorphy 28. It has a banded wing but plain brown abdomen. It may belong to the drakensbergensis group but, as presently understood, the loss of wing pigmentation occurred before loss of abdominal pigmentation pattern, which would conflict with what is present in C. gilva . In addition, C. gilva has synapomorphy 40 (pedicel with strong setae), which would place it higher up in the phylogeny of the Corethrellidae . The discovery of the male of this species would help in its placement.

TYPES: Holotype, female adult on microscope slide, labeled " HOLOTYPE Corethrella gilva Borkent and Grafe ", " 12 km S. Liang, Brunei, 15-V-2007; on Hylarana glandulosa ; U. Grafe; 34-1/1, DNA extracted", "34-1/1 231007 " (CNCI). Paratypes on microscope slides: 1 Ƥ, from type locality, but 10-V-2007 (CNCI); 1 Ƥ, from type locality but 15-V-2007 (CNCI);1 Ƥ, from type locality but 23-V-2007 (CNCI); 1 Ƥ, from type locality but 9-VI- 2007 (UBD); 7 Ƥ, from type locality but 11-XII-2007; 1 Ƥ, from type locality but 28-V-2007 (UBD); 1 Ƥ, 15 km S. Liang, Brunei, 40 m, 9-V-2007 (CNCI); 1 Ƥ, from previous locality but 22-V-2007 (CNCI); 1 Ƥ, lower Sungai Apan, 0.9 km E. headquarters, Ulu Temburong National Park, Brunei, 110 m, 9-II-2010 (CNCI); 1 Ƥ, tributary of Sungai Belalong, Temburong, Brunei, 110 m, 115° 09'E, 4° 33'N, 7-VIII-2006 (CNCI). Paratypes on pins: 3 Ƥ, lower Sungai Apan, Ulu Temburong NP, Brunei, 110 m, 5-II-2010 (2 CNCI; 1 UBD); 1 Ƥ, from previous locality but 13-VII-2008 (CNCI); 2 Ƥ, Temburong, Ulu Temburong NP, Brunei, 7-VII-2008 (CNCI); 1 Ƥ, 12 km S. Liang, Brunei, 30 m, 11-VI-2007 (CNCI); 1 Ƥ, from previous locality but 11-VI-2011 (CNCI); 1 Ƥ, from previous locality but 28-V-2007 (CNCI); 2 Ƥ, from previous locality but 4-VI-2007 (CNCI; UBD); 1 Ƥ, from previous locality but 23-V-2007 (CNCI); 1 Ƥ, from previous locality but 9-VI-2007 (CNCI); 4 Ƥ, from previous locality but 15-V-2007 (CNCI); 1 Ƥ, from previous locality but 4-XI-2010 (CNCI); 1 Ƥ, 12.5 km S. Liang, Brunei, 33 m, 21-II-2009 (CNCI); 1 Ƥ, from previous locality but 3-I-2009 (CNCI); 1 Ƥ, 15 km S. Liang, Brunei, 40 m, 5-VI-2007 (CNCI); 2 Ƥ, from previous locality but 12-V-2007 (CNCI); 1 Ƥ, from previous locality but 22-V-2007 (CNCI); 1 Ƥ, 17 km N. Labi, Brunei, 40 m, 14-V-2007 (CNCI); 1 Ƥ, Sungai Ingei, 8.2 km S. Melilas, Brunei, 50 m, VII-2010 (CNCI); 1 Ƥ, from previous locality but 10-VII-2010 (CNCI).

DERIVATION OF SPECIFIC EPITHET: The name gilva (yellow) refers to the lightly pigmented hind tibiae 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 7. A – D. Head capsules of female Corethrella, anterior view. E – H. Antennal flagellomeres 1 – 4 of female.

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 16. A – B. Distributions of species of Corethrella from Borneo.