Simulium curtatum, Jitklang, Sanae, Kuvangkadilok, Chaliow, Baimai, Visut, Takaoka, Hiroyuki & Adler, Peter H., 2008

Jitklang, Sanae, Kuvangkadilok, Chaliow, Baimai, Visut, Takaoka, Hiroyuki & Adler, Peter H., 2008, Cytogenetics and morphotaxonomy of the Simulium (Gomphostilbia) ceylonicum species group (Diptera: Simuliidae) in Thailand, Zootaxa 1917, pp. 1-28 : 14

Simulium curtatum n. sp.

(Figs. 6B, 7B, 9B, 11B, 12)

Diagnosis: This species is distinguished morphologically from all other cytoforms of the group by having the stalk of the ventral pair of gill filaments longer than the stalk of the middle triplet, and from all other cytoforms, except S. inthanonense , by having a small postgenal cleft.

This species differs morphologically from S. asakoae as follows:

Female. Sensory vesicle ca. 0.6 x as long as 3rd segment of maxillary palp (Fig. 12C); mid tibia and hind basitarsus darker. Male. Upper eye of 13 vertical columns and 16 horizontal rows of large facets; anterior and posterior margins of ventral plate slightly convex (Fig. 12I). Pupa. Gill filaments ( Fig. 11 B) (3) or (1 + 2) + (1 + 2) + 2 from dorsal to ventral; terminal hooks each with serrated outer margin. Larva. Head spots faintly positive; postgenal cleft ( Fig. 9 B) ca. 1.1–1.4 x as long as postgenal bridge; abdominal segments I–III with greenish transverse bands, segment V with reddish-brown transverse band dorsally.

Chromosomes. The polytene chromosomes of 23 larvae from two populations (sites 6 and 14) stained well. The centromere regions were not expanded. The banding sequence differed from standard by more than seven fixed inversions: IS-4 (Fig. 2A) IIS-5 (Fig. 4A), IIL-7.8, IIL-9 (Fig. 5A), IIIS-2, and multiple inversions in IIIL (IIIL-complex 2, Fig. 6B). We found two floating inversions, IL-2 (Fig. 2B) and IIIL-9 (Fig. 6B).

Type specimens. Holotype: Male, with associated pupal exuviae and cocoon (in ethanol vial). THAI- LAND, Chiang Mai Province, Siriphum waterfall, Doi Inthanon National Park, 18º32'N 98º30'E, 24.VII.2005, S. Jitklang and C. Kuvangkadilok. Paratypes: 1 male and 1 female (in glycerin vial), 2 pupae, and 4 mature larvae (transferred from Carnoy’s fixative to 95% ethanol), same data as holotype.

Bionomics. Pupae and larvae were collected from fallen leaves in narrow streams (0.2–2.5 m wide) with low conductivity (mean = 25.03 µs/cm) at high altitudes (950–1615 m) ( Table 3 ). This species was collected with S. asakoae , S. chamlongi , S. inthanonense , S. feuerborni , S. doipuiense , and S. yuphae .

Etymology. The specific name curtatum is from Latin, meaning “short”, in reference to the short postgenal cleft of the larva.

Figures

FIGURE 9. Postgenal clefts of larvae of 10 cytoforms of the Simulium ceylonicum species group in Thailand. (A) S. asakoae, (B) S. curtatum n. sp., (C) S. nr. asakoae 2, (D) S. nr. asakoae 3, (E) S. nr. asakoae 4, (F) S. sheilae, (G) S. trangense n. sp., (H) S. doisaketense n. sp., (I) S. nr. sheilae 3, and (J) S. inthanonense. Scale bar = 0.1 mm.

FIGURE 11. Gill filaments of 10 cytoforms of the Simulium ceylonicum species group in Thailand. (A) S. asakoae, (B) S. curtatum n. sp., (C) S. nr. asakoae 2, (D) S. nr. asakoae 3, (E) S. nr. asakoae 4, (F) S. sheilae, (G) S. trangense n. sp., (H) S. doisaketense n. sp., (I) S. nr. sheilae 3, and (J) S. inthanonense. Scale bar = 0.1 mm.