Corethrella (Corethrella) calathicola Edwards

Borkent, Art & Grafe, Ulmar, 2012, The Frog-Biting Midges of Borneo — From Two to Eleven Species (Corethrellidae: Diptera), Zootaxa 3279, pp. 1-45 : 14-15

Corethrella (Corethrella) calathicola Edwards

( Figs. 5 B, 7A, F, H, 8H, 10C, 11C, 12H, 13G, 18)

Corethrella calathicola Edwards 1930:529 . Type locality: Singapore, Malaysia. Lectotype male (BMNH). Mogi and Yong 1992:180; Borkent 2008:145.

DIAGNOSIS: Male and female adults: Only extant species of Corethrella in the Oriental, Australasian, and Oceanic Regions with the combination of a pale or light brown palpus (contrasting with dark brown clypeus) ( Fig. 7A ), patterned wing (with a midlength band, darker where R1 joins the costa) ( Fig. 12H ), uniformly dark brown midfemur, hind tibia with dark pigmentation at base and apex ( Fig. 10C ), and with abdominal tergites 2–6 uniformly brown ( Fig. 13G ). Only extant species in Borneo with the combination of well-developed scales on midfemur ( Fig. 11 C); also only species with palpus entirely pale and contrasting with a dark clypeus ( Fig. 7A ) and with distinct dark pigmentation at both base and apex of hind tibia ( Fig. 10C ).

DESCRIPTION: This species was redescribed by Borkent (2008), but see Taxonomic Discussion below.

DISTRIBUTION AND BIONOMICS: Corethrella calathicola is known from Singapore, Malaysia, Indonesia and Brunei ( Fig. 18 ) at altitudes ranging from 1–1083 m. In Borneo, it has been recorded only from Brunei, Sarawak, Malaysia and eastern Kalimantan, Indonesia. This is the only species of Corethrella recorded from and restricted to species of Nepenthes . Its biology has been summarized by Borkent (2008). Habitats include lowland and mid-elevation peat swamp in Brunei ( Fig. 1 A). Previously recorded from N. ampullaria (Jack) , there were earlier records of an unnamed Corethrella species from N. bicalcarata (Hook) . Here we confirm that C. calathicola occurs in N. bicalcarata in Brunei as well as in N. veitchii (Hook) in the Bario highlands of Sarawak. We have found it commonly in N. ampullaria in Brunei as well ( Fig. 1 B). Immatures of C. calathicola were found in these three species of Nepenthes only when they were on or near the ground (both authors, pers. obs.; Miyagi pers. comm.).

We reared nine males and five females from 14 larvae collected from N. ampullaria and N. bicalcarata . Aside from rearings, we examined female adults collected with frog-call traps in Brunei and Lanjak Entimau, Sarawak, as well as feeding on a calling male of one species of frog (Table 7). We examined the specimens reared from N. ampullaria at Matang, Sarawak, Malaysia noted by Miyagi et al. (2009).

TAXONOMIC DISCUSSION: Borkent (2008) described the pigmentation of the male abdomen as having "segments 1–7, 9 light to medium brown, segment 8 pale". Some of our fresh slide-mounted material matches this description but at least some fresh material in alcohol or pinned (from Brunei, some from Bario, Sarawak) had tergites 2–7 pale and contrasting with a dark tergite 1 and darker sternites. Upon treatment with KOH, some specimens with lighter tergites had tergites and sternites appeared uniformly medium brown but in others, the lighter tergites were discernible. We are puzzled as to why there was this difference between alcohol and slidemounted material when this is not the case with other Corethrella specimens studied by Borkent (2008). The abdomens of all females were entirely medium to dark brown, so that there is a clear sexual dimorphism in pigmentation of the abdomen in at least some members of C. calathicola . More study and specimens are needed to further interpret this variation.

There was significant variation in the relative sizes of flagellomeres 1–3 in the female C. calathicola we examined. In specimens from Brunei they were relatively short ( Fig. 7 F), compared to those from Matang, Sarawak ( Fig. 7 H) and other sites recorded and illustrated by Borkent (2008, fig. 30H).

Borkent (2008) designated the lectotype for C. calathicola and listed the paralectotypes known to him. There are an additional two larvae that should be considered paralectotype specimens on separate slides in the BMNH. Both are from Singapore and taken from a "pitcher plant" (Zoe Adams, pers. comm.).

Corethrella calathicola belongs to the appendiculata species group, a group that otherwise includes only New World species occupying treeholes and is the sister species of the Neotropical C. melanica Lane and Aitken ( Borkent 2008) .

MATERIAL EXAMINED: In addition to the material listed by Borkent (2008), we examined the following on microscope slides: 1 3, 12 km S. Liang, Brunei, 30 m, 9-VIII-2009, from Nepenthes ampullaria ( CNCI);1 Ƥ, from previous locality but 18-V-2007 ( CNCI); 2 Ƥ, 15 km S. Liang, Brunei, 40 m, 12-V-2007 (1, CNCI; 1, UBD); 2 Ƥ, from previous locality but 5-VI-2207 ( CNCI); 3 Ƥ from previous locality but 22-V-2207 ( CNCI); 2 Ƥ, 17 km S. Liang, Brunei, 40 m, 6-IV-2009 (1, CNCI; 1, UBD); 2 3, Bario, Sarawak, Malaysia, 1060 m, 6-IX-2009, reared from Nepenthes veitchii ( CNCI); 1 3, from previous locality but 17-IX-2006 ( CNCI); 1 3, Pa Umor, 5 km E.

Bario, 03°44.118' N 115°30.404'E, 1083 m, Sarawak, Malaysia, 17-IX-2006, reared from 'pitcher plant' ( CNCI); 2 3, 2 Ƥ, Matang, Sarawak, Malaysia, 200 m, 28-VIII-2006, reared from 'pitcher plant' (1 3, 2 Ƥ, CNCI; 1 3, UBD). Pinned specimens:1 Ƥ, 12.5 km S. Liang, Brunei, 33 m, 10-I-2009 ( CNCI); 2 3, 12 km S. Liang, Brunei, 30 m, 9- VIII-2009 ( CNCI); 1 3, 2 Ƥ, previous locality but 23-VII-2009 (2 Ƥ, CNCI; 1 3, UBD); 1 3, 1 Ƥ, previous locality but 20-VII-2009 ( CNCI); 2 3, from previous locality but 30-VII-2009 (1, CNCI; 1 UBD); 2 Ƥ, from previous locality but 9-VIII-2009 ( UBD); 1 Ƥ, from previous locality but 15-V-2007 ( CNCI); 2 3, from previous locality but 25-VII-2009 ( CNCI); 4 Ƥ, 15 km S. Liang, Brunei, 40 m, 22-V-2007 ( CNCI); 1 Ƥ, 17 km S. Liang, Brunei, 40 m, 17-V-2007 ( CNCI); 1 Ƥ, Lanjak Entimau, Sarawak, Malaysia, 80 m, 28-II-2011 ( SMKM).

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 18. Distribution of Corethrella calathicola.

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

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).