Simulium (Eusimulium) satsumense

Kim, Sam-Kyu, 2020, A new record of the subgenus Eusimulium Roubaud from Korea with an updated key to genera and subgenera of Korean black flies (Diptera: Simuliidae), Journal of Species Research 9 (2), pp. 174-179 : 176-178

publication ID	https://doi.org/ 10.12651/JSR.2020.9.2.174
persistent identifier	https://treatment.plazi.org/id/364287EE-FFCF-FFA3-FCE1-2F16FBD9D26C
treatment provided by	Felipe
scientific name	Simulium (Eusimulium) satsumense
status

Treatment

Takaoka, 1976 ( Figs. 1-3 View Fig View Fig View Fig )

Simulium (Eusimulium) satsumense Takaoka, 1976: 171 View in CoL . Type locality: Nansei Island , Japan.

Simulium (Eusimulium) satsumense View in CoL : Takaoka, 1977: 219 (Japanese key); Ono, 1980: 350 (remark); Takaoka, 2002 (Japanese key); Takaoka & Shrestha, 2010 (remark); Saito, 2015: 15 (Japanese list and names); Al- der, 2019: 45 (world checklist).

Diagnosis. This species can be distinguished from oth- er Korean black flies by the following combination of characteristics: pupa with cocoon slipper-shaped; gill of 4 slender filaments, dorsalmost filament strongly divergent from other filaments, longer than pupal body; head and thorax densely covered with numerous minute tubercles; abdominal segments VI- VIII with small stout spines; terminal hook small; larva with head spot distinctly positive, anteromedial spots as long as posteromedial spots; antenna with proximal article brown; postgenal cleft small, apically rounded, squared or dull pointed; gill histoblast of 4 filaments, inverted P-shaped; ventral tubercle prominent, conical shaped; rectal papillae of 3 simple lobes.

Description. Pupa ( Fig. 1 View Fig ). Body length: 3.2-4.0 mm (n = 9). Body brown to reddish brown ground color. Gill ( Fig. 1A, B, D View Fig ) of 4 slender filaments in 2 + 2 arrange- ment, longer than pupal body length (4.5-4.9 mm); upper pair with short stalk, lower pair sessile; dorsalmost filament directed upward then perpendicularly bending forward, angle between uppermost and lowermost filaments about 90°; upper filament of lower pair (3 rd filament from dorsal to ventral) directed outwardly then forwardly. Cephalic plate and vertex ( Fig. 1E View Fig ) densely covered with small tubercles. Frons with 2 pairs of medium long trichomes (0.08-0.1 mm), simple, as long as or little shorter than facial trichome; face with 1 medium long trichome (0.1-0.12 mm), simple. Thorax ( Fig. 1F View Fig ) densely covered with small tubercles; thoracic trichome ( Fig. 1 View Fig ) in 6 pairs, simple (unbranched), long (0.12-0.17 mm). Abdomen ( Fig. 1C View Fig ). Abdominal tergites III and IV with 4 anteriorly directed spin hooks on posterior margin. Tergites VI- VIII with small spines or spine combs, spines on tergite VI the smallest, tergite VIII the largest. Tergite IX with small spine combs. Terminal hooks distinct, small. Cocoon ( Fig. 1A, B View Fig ) slipper shaped, tight- ly woven, longer than pupa, completely covered pupal body (3.3-4.4 mm).

Larva ( Fig. 2 View Fig ). Body length 6.3-6.7 mm (n = 9). Body ( Fig. 2A- C View Fig ) grayish brown ground color. Gill histoblast ( Fig. 2F View Fig ) 4 filaments, proximal portion of the uppermost filament bent perpendicularly, inverted P-shaped. Head ( Fig. 2D, E View Fig ) with head spots distinctly positive; anteromedial spots 6-7, close together, lying in straight line, as long as posteromedial spots, distinct; first and second anterolateral spots obliquely elongated, close together, distinct; posteromedial spots narrow, lying in straight line, distinct; first and second posterolateral spots separated, distinct. Single spot under ocellus, two spots pos- terolaterally. Antenna ( Fig. 2D View Fig ) pale yellow with proximal and distal article brown, 1.25X as long as labral fan stem, proportional ratio of antennal segments with 1: 1.3-1.4: 0.76-0.9. Labral fan with 53-55 primary rays. Postgenal cleft ( Fig. 2G View Fig ) small, apically rounded, squared or dull pointed, sometime apical portion not well defined, little wider than long, laterally with elon- gate spot and round spot. Hypostoma ( Fig. 2H View Fig ) with 9 teeth, lateral and median teeth prominent, subequal in length, basally with 4-5 hypostomal setae. Subesopha- geal ganglion darkly pigmented. Thorax and abdomen almost bare, with very minute whitish setae posterodor- sally. Rectal papillae ( Fig. 2I View Fig ) of 3 simple lobes. Ventral tubercle prominent, conical shaped ( Fig. 2I View Fig ). Posterior proleg ( Fig. 2J, K View Fig ) with 12-14 hooks (posterior circlet) in 68-72 rows.

Specimens examined. Korea: Gyeonggi-do, Yeoju-si, Gangcheon-myeon, Dojeon-ri , 649-1. 37°20′42″N, 127° 44′54″E, altitude 149 m. 31.v.2019, SK Kim (15 pupae, 9 ultimate, 7 penultimate, 5 early instar larvae) GoogleMaps .

Distribution. Korea (new record), China (Liaoning), Japan (Nansei Islands).

Stream information. The stream ( Fig. 3A View Fig ), the only locality where the larvae and pupae of S. (E.) satsumense were collected so far, adjacent to agricultural fields and small residence area, was medium-sized stream with less than 10 m wide and 15 cm deep with very slow flowing with relatively clean water. The streambed was mainly consisted of small stones and rubble with sandy bottom along with many submerged broad-leaved vegetations where the larvae and pupae were attached themselves to those various substrates. The stream was totally ex- posed to the sun with partly shaded by concrete overhead bridge.

Remarks. All members of the subgenus are multivoltine and spend a portion of the winter in the egg stage ( Adler et al., 2004). Pupa of S. (E.) satsumense is morphologically very similar to that of S. (E.) jomsomense Takaoka & Shrestha from Nepal in many ways, making it unprac- tical to distinguish them from one another. They can be separated by female ovipositor and male legs characteristics ( Takaoka & Shrestha, 2010).

According to Takaoka (1976), larvae and pupae of the species were collected from trailing grasses in a very sluggish ditch for rice fields on 15 Jan. 1974 in Nansei Island (= Ryukyu Island, Okinawa), with normal temperature of January around 14.7℃, assuming its year-round occurrence in Japan, at least in southern part of the Japan. For Korean species, early to ultimate instar larvae along with many pupae were collected only once from a single stream with very slow flowing on 31 May 2019 with average temperature of 16℃. It is premature to assume its multiple occurrences in Korea. More detailed study is warranted to determine its voltinism in Korea. Larvae and pupae were mainly attached themselves to small stones, rubbles or submerged vegetation ( Fig. 3B, C View Fig ) and collect- ed along with other black flies such as, S. (S.) arakawae , S. (S.) bidentatum , S. (S.) iwatense , S. (S.) suzukii , and S. (N.) uchidai . Among the collected specimens, two penultimate instar larvae were patently infected with an unidentified microsporidian fungus.