Ecnomus sakishimensis, Kuhara, Naotoshi, 2016

Kuhara, Naotoshi, 2016, Revision of Japanese species of the genus Ecnomus McLachlan (Trichoptera: Ecnomidae), with descriptions of two new species, Zootaxa 4114 (5), pp. 561-571 : 568-570

Ecnomus sakishimensis sp. nov.

( Figs. 5 A–G, 6)

Diagnosis. The male of this species is somewhat similar to that of E. ramayana Malicky & Chantaramongkok 1993 described from Thailand, but can be distinguished from the latter and also other Ecnomus species by the unique shape and structure of the inferior appendages which are short and subtriangular in lateral aspect and have a mesal projection. The female is characterized by the ventral plates of segment VIII, which are relatively small and constricted in the basal half.

Description. Adult ( Fig. 5 ). Length of each forewing of male 3.5–5.0 mm (mean = 4.3 mm, n = 13), female 3.7–5.1 mm (mean = 4.5 mm, n = 8). General appearance similar to E. japonicus .

Male genitalia ( Fig. 5 A–E). Tergum IX short, about 1/2 to 2/3 as long as sternum IX ( Fig. 5 A); anterodorsal margin deeply notched ( Fig. 5 B); sternum IX without longitudinal median line; anteroventral margin shallowly excised; posterior margin nearly straight ( Fig. 5 C). Segment X represented by pair of short, broad plates, each with 3 setae along posteromesal margin ( Fig. 5 B). Superior appendages slender, long, almost parallel-sided with round apices in lateral aspect ( Fig. 5 A), weakly curved inward in dorsal aspect ( Fig. 5 B); inner surfaces concave, bearing black peg-like stout setae along dorsal and apical margins in distal 1/3 ( Fig. 5 B); finger-like projection arising from each ventrobasal corner, with 2 setae apically ( Fig. 5 B). Inferior appendages short, as long as high, not reaching posterior end of superior appendages, subtriangular in lateral aspect ( Fig. 5 A); each with inner projection curved dorsomesad, tapered to apex ( Figs. 5 A, 5C); basal plate semisclerotized, with pair of small lateral projections at midlength ( Fig. 5 C). Phallus bulbous basally, acute apically, sclerotized laterally and membranous dorsally, including pair of sclerites; parameres moderately screlotized, flattened, subtriangular in lateral aspect, directed posterodorsad; dorsobasal lobe distinct ( Fig. 5 E).

Female genitalia ( Figs. 5 F, 5G). Ventromesal plate of sternum VII absent. Ventral plates of sternum VIII relatively small, constricted in lateral aspect ( Fig. 5 F) and projecting anterad laterally at basal 1/3rd to 1/2nd; each with basal part adhering to main body of segment; distal part flap-like, each with 3 long setae along posterior margin ( Figs. 5 F, 5G). Segment X with small sclerites on posterior unpigmented portion ( Fig. 5 F). Segment XI setose, well pigmented ( Figs. 5 F, 5G).

Holotype. male (in alcohol), Japan, Ryûkyû Islands, Iriomote-jima, Taketomi-chô, Ômijya-gawa, Ômijyabashi, 24.39ºN, 123.86ºE, 24.iii.1999, TI & AO ( SEHU).

Paratypes. 4 males, (in alcohol), same data as holotype ( CBM); 5 males, Iriomote-jima, Taketomi-chô, Airagawa, nr. R. 217, 28–30.x.2012, TI ( SEHU); 3 males (in alcohol), Iriomote-jima, Taketomi-chô, Aira-gawa, 13– 17.iii.2002, T. Yoshida & H. Sugaya ( CBM).

Other specimens. [Ryûkyû Islands] Ishigaki-jima: 6 males, 3 females, Ishigaki-shi, Hakusui, Nagura-gawa, el. 3–28 m, 13–21.x.1999, K. Konishi; 2 males, 1 female, ibid, 11–15.iv.2005, TI; 1 female, ibid, 22.iii.2009, TI. 1 male, ibid, 11.iii.2011, TI; 1 female, ibid, 12.iv.2011, TI; 3 males, 14 females, ibid, 25–26.x.2012, TI; 1 male, Ishigaki-shi, Nagura-gawa, el. 95 m, 26.x.2012, TI; 1 male, 3 females, Ishigaki-shi, tributary of Nagura-gawa, el. 9 m, 11–13.iv.2011, TI; 2 males, 1 female, Ishigaki-shi, stream nr. Nagura-dam, el. 70 m, 11.iv.2011, TI. Iriomotejima: 1 male, Taketomi-chô, Aira-gawa, 24.iii.1999, TI & AO; 1 male, 2 females, ibid, 13–17.iii.2002, T. Yoshida & H. Sugaya; 2 females, ibid, 1.xii.2013, TI; 1 male, Taketomi-chô, Ôtomi, Nishifunatsuki-gawa, 23.iii.1999, TI & AO; 1 female, ibid, 30.x.2012, TI; 2 males, same data as holotype; 1 male, type locality, 13.iv.2005, TI; 4 females, type locality, 9.x.2012, TI.

Etymology. Named for its distribution in the Sakishima Islands, which is the southern part of the Ryûkyû Islands, including Ishigaki-jima and Iriomote-jima.

Distribution. Japan: Ryûkyû Islands (Ishigaki-jima, Iriomote-jima).

Habitat. The above specimens were collected beside streams and rivers, mainly in the middle reaches.

Remarks. This species belongs to the E. connatus Group of Li & Morse (1997), because the phallus is bulbous basally and acute apically, the superior appendages are elongate, and sternum IX lacks a longitudinal median line. The Ryûkyû Islands, except the northern part, are usually considered to be included in the Oriental region ( Toda et al. 2003), hence this is an Oriental species.

Figures

FIGURE 5. Ecnomus sakishimensis sp. nov. (type locality; 5 A – 5 C, holotype). 5 A – 5 C, male genitalia: 5 A, left lateral; 5 B, dorsal; 5 C, ventral; 5 D, male phallus and inferior appendages, dorsal; 5 E, phallus, left lateral; 5 F – 5 G, female genitalia: 5 F, left lateral; 5 G, ventral.