Corethrella (Corethrella) brunnea Borkent

Borkent, Art & Grafe, Ulmar, 2012, The Frog-Biting Midges of Borneo — From Two to Eleven Species (Corethrellidae: Diptera), Zootaxa 3279, pp. 1-45 : 11-13

Corethrella (Corethrella) brunnea Borkent

( Figs. 4 E, 12E, 14B)

Corethrella brunnea Borkent 2008:56 . Type locality: 1st Div., Semongoh Forest Reserve, 1° 25' N 110° 17'E, Sarawak, Malaysia. Holotype Ƥ (BMNH).

DIAGNOSIS: Male adult. Unknown. Female adult. Only extant species of Corethrella in the Palaearctic, Oriental, Oceanian and northern Australasian Regions with the combination of about 23 setae on the clypeus, a plain wing (no pattern) ( Fig. 12E ), wing with well-developed scales on all the wing veins, and an entirely dark brown thorax. Only extant species in Borneo with the combination of about 23 setae on the clypeus, a plain wing (no pattern) ( Fig. 12E ), and an entirely dark brown thorax ( Fig. 4 E).

DESCRIPTION AND TAXONOMIC DISCUSSION: This species, known only from the female adult holotype from Sarawak, Malaysia ( Fig. 14B ), was described and interpreted by Borkent (2008). It is a member of the drakensbergensis species group ( Fig. 19 ). The type locality is in lowland mixed dipterocarp forest.

Corethrella (Corethrella) mitra Borkent & Grafe , new species ( Figs. 3 B, 4F, 6E, 8F, 10A, 12F, 13E, 16B)

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 plain wing ( Fig. 12F ), flagellomeres 1–4 elongate ( Fig. 8 F) and the scutum a lighter brown, contrasting with darker pleura ( Fig. 10A ). Only extant species in Borneo with the combination of a plain wing ( Fig. 12F ) and the scutum a lighter brown, contrasting with a uniformly darker pleura ( Fig. 10A ).

DESCRIPTION: Male adult. Unknown. Female adult. Descriptive statistics: See Tables 1 –5. Head: Outline in anterior view somewhat circular ( Fig. 6 E). 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 F; sensilla coeloconica on flagellomeres 1–2 (3), 7–13, only flagellomere 1 with more than one; flagellomere 13 with well-developed apical bifurcation. Clypeus ( Fig. 6 E) somewhat square. Mandible with moderately small, pointed teeth. Palpus ( Fig. 6 E) brown; segment 3 swollen apically. Thorax ( Fig. 10A ): Scutum mostly light to medium brown, contrasting with darker brown pleura; scutellum, mediotergite, most of pleura dark brown, 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. 12F ): Apex of R2 slightly distal to apex of M1. Plain, without pattern of pigmented veins and/or scales; veins (other than costa and wing margin) with slender scales. Halter dark brown, equal to scutellum. Legs ( Fig. 10A ): Light brown, with about basal 0.5 hind femur slightly darker. 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. 13E ): Medium brown, with tergites and sternites uniformly medium brown or at least tergites 2–5 with posterior margins pale, sternites medium brown, segments 8–9 medium brown. Cercus medium brown.

Immature stages. Unknown.

DISTRIBUTION AND BIONOMICS: Corethrella mitra is known from female specimens collected in Ulu Temburong National Park in Brunei and the Malaysian states of Sabah and Sarawak 60–340 m ( Fig. 16B ). Habitats are in steep terrain in mature mixed dipterocarp forest ( Fig. 1 E, F). They were collected feeding on calling males of three species of frogs and have not yet been collected with a frog-call trap (Table 7).

TAXONOMIC DISCUSSION: Female adults have variably pigmented abdomens with some from Kuala Belalong Field Study Centre or nearby Sungai Esu in Ulu Temburong NP, Brunei having uniformly pigmented abdomens and others, like C. mitra from elsewhere, with at least tergites 2–5 brown anteriorly and pale posteriorly. We initially thought these two forms represented two species (the feature separates other species) but could find no other differences. The two forms were collected together on a single evening at Sungai Esu and we presently consider this to be intraspecific variation.

Corethrella mitra is placed in the drakensbergensis species group for the same reasons and with the same limitations as indicated for C. nanoantennalis ( Fig. 19 ). The uniform wing of C. mitra (synapomorphy 25) indicates that it belongs further within the group ( Fig. 19 ). This uniform wing, however, is susceptible to homoplasy and is, at best, a weak indicator of relationship. Overall, C. mitra is otherwise quite similar to C. nanoantennalis and C. bipigmenta .

TYPES: Holotype, female adult on microscope slide, labeled " HOLOTYPE Corethrella mitra Borkent and Grafe ", "lower Sungai Apan, Ulu Temburong National Park, Brunei, 4-vii-2008; on L. leporinus, U. Grafe; 6" (CNCI). Paratypes on microscope slides: 2 Ƥ, labeled as for holotype but 1-vii-2008 (1, CNCI; 1 UBD). Paratypes on pins: 2 Ƥ, 0.5 km S. Kuala Belalong Field Studies Centre, along Sungai Esu, Brunei, 60 m, 12-XI-2010 (CNCI); 2 Ƥ, Kuala Belalong Field Studies Centre, Brunei, 50 m, 16-17-XI-2010 (CNCI); 1 Ƥ, lower Sungai Apan, Ulu Temburong National Park, Brunei, 110 m, 19-VII-2008 (CNCI); 2 Ƥ, from previous locality but 1-VII-2008 (CNCI; UBD); 2 Ƥ, from previous locality but 8-VII-2008 (CNCI; UBD); 1 Ƥ, SMI, Belalong, Ulu Temburong NP, Brunei, 26-VI-2010 (CNCI); 1 Ƥ, 34 km NE Kalabakan, Sabah, Malaysia, 340 m, 26-VIII-2011 (CNCI); 4 Ƥ, 30 km NE Kalabakan, Sabah, Malaysia, 300 m, 17-V-2011 (CNCI); 1 Ƥ, Lanjak Entimau, (112° 4'E, 1° 28'N), Sarawak, Malaysia, 80 m, 25-VI-2008 (CNCI).

DERIVATION OF SPECIFIC EPITHET: The name mitra (crown) refers to the relatively paler scutum compared to the darker pleura 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 4. Habitus of adult female Corethrella, in lateral view, A – D, F in alcohol, E on microscope slide. C, F, with blood meal apparent in abdomen.

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

FIGURE 10. A – D. Thoraces and legs of female Corethrella, lateral view; slide-mounted.

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

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