Indosialis siamensis, Piraonapicha & Sangpradub & Jaitrong & Liu, 2020

Piraonapicha, Kanyakorn, Sangpradub, Narumon, Jaitrong, Weeyawat & Liu, Xingyue, 2020, The alderfly genus Indosialis Lestage, 1927 (Megaloptera: Sialidae) in Thailand and Laos, with a description of a new species, Zootaxa 4786 (2), pp. 233-253 : 246-250

Indosialis siamensis sp. nov.

( Figs. 10–15 )

Type material. Holotype, male, northeastern Thailand, Huai Lek Stream, Wang Saphung District , Loei Province, 17°21’9.76”N, 101°39’23.78’’E, 336 m a.s.l., 30.III.2020, K. Piraonapicha leg., THNHM-I-16801 ( THNHM, Pinned specimen) . Paratypes. Three males (THNHM-I-16802 to THNHM-I-16804, THNHM), 1 female (THNHM- I-16805, THNHM), same locality and collector as holotype, 13. V.2019; 1 female (THNHM-I-16806, THNHM), same locality and collector as holotype, 28. V.2019; 1 male (KKUM-001, KKU) and 2 females (KKUM-002 to KKUM-003, KKU), same locality and collector as holotype, 30. VI.2019; 1 male (KKUM-004, KKU), same locality and collector as holotype, 14.II.2020 . The paratypes are preserved in absolute ethanol.

Diagnosis. Head and prothorax brown in both sexes. Male. Inner margin of left mandible without small setae; inner margin of right mandible with distinct apical tooth followed by long and sharp preapical tooth and broad basal tooth; gonocoxite 9 in lateral view broadly rounded, with apex slightly narrowed and curved dorsad; ectoproct in lateral view subtriangular, with convex apex.

Description. Male (holotype and paratypes, Figs. 10 , 12 , 13 , 15 ). Body length 7.5 mm; right forewing length 7.0 mm; right forewing width 2.5 mm, right hind wing length 6.5 mm; right hind wing width 2.5 mm.

Head brown, subquadrate, almost as long as broad; dorsum of head with dense brownish irregular raised scars on posterior half; labrum brown, elliptical, clearly shorter than broad, anterior margin weakly concave, and covered with dense long erect setae; mandibles asymmetrical, smooth and shiny; left mandible with long and blunt apical tooth, followed by broad preapical tooth and small triangular basal tooth; basal margin of left mandible feebly concave; without setae on inner margin of mandible; outer margin of left mandible feebly convex ( Fig. 12A ); right mandible with distinct (small and sharp) apical tooth, followed by large, long and sharp preapical tooth and broad basal tooth on inner margin; outer margin of right mandible convex ( Fig. 12B ); clypeus yellowish brown, relatively short, and its anterior margin concave medially; compound eye dark, relatively large and roundly convex, located anterior to mid-length of head; scape and pedicel yellowish brown, scape almost twice as long as pedicel, flagellum dark brown.

Thorax brown; pronotum (excluding anterior and posterior membranes) in dorsal view, subrectangular, clearly shorter than broad, with almost parallel lateral margins; setae on pronotum brown; mesonotum in dorsal view, subrectangular, almost as long as metanotum. Wings grayish brown; veins brown; forewing about 2.80 times as long as broad; costal region with 6–8 distinct cross-veins; hindwing slightly shorter than forewing, about 2.60 times as long as broad; costal region with 3 distinct costal crossveins; wings entirely covered with dense erect long setae mixed with dense short setae. Legs covered with decumbent setae (setae on legs clearly longer than on wings); coxae yellowish brown; femora, tibiae and tarsi brown (tarsi darker than former two), pretarsal claws pale brown.

Abdomen brown, abdominal segments 1–8 each with a pair of yellow spots medially.

Genitalia. Tergum 9 in dorsal view, subtrapezoidal, with its anterior margin weakly convex and posterior margin extensively concave; sternum 9 in ventral view, as long as broad, with anterior margin almost straight and posterior margin extensively convex; gonocoxite 9 in lateral view, broad, ventral margin convex, dorsal margin weakly sinuate with posterodorsal corner slightly produced; ectoproct in lateral view, subtriangular, convex distal and curved inward; fused gonocoxites 11 in lateral view, with narrowed, gonostyli 11 directed posteriorly; in dorsal view, gonostyli 11 present as a pair of relatively stout spines, which are narrowed gradually to apex. Large sac-like structure present in male genitalia ( Fig. 13 ).

Female (paratypes, n = 3, Fig. 11 , 12 , 14 ). Body length 7.5–8.5 mm; right forewing length 8.5–9.5 mm; forewing width 2.5–3.0 mm; right hindwing length 7.5–9.0 mm; right hindwing width 3.0– 3.5 mm.

Similar to the male in structure, sculpture, color, wing venation and pilosity, with the following condition that should be noted: Body slightly larger; mandibles symmetrical, each with large and blunt apical tooth, followed by medium-sized of blunt tooth and small triangular basal tooth ( Fig. 12C ); sternum 7 broadly pentagonal in ventral view; gonocoxites 8 separated into a pair of subrectangular lobes, partly concealed under sternum 7; gonapophysis 8 subtrapezoidal, clearly shorter than broad, with some setae; gonocoxites 9 present a pair of broad ovoid valves, with small gonostyli 9 at tip; ectoprocts paired, small, and ovoid ( Fig. 14 ).

Etymology. The specific name is an adjective meaning ‘of siam (a historic name of Thailand)’.

DNA barcode data. In the maximum likelihood and neighbor-joining analyses, the adult males and females of I. siamensis from Loei Province were genetically distinct from I. bannaensis ( Fig. 16 ), being consistent to the morphological identification. The COI intraspecific divergence ranged from 0 to 0.023, while the interspecific divergence between the two Thai Indosialis species ranged 0.043 to 0.062 (GenBank Accession Numbers: MN087710 – MN0815).

Habitat. The adults of I. siamensis were collected by light traps close to a slow-flowing or sluggish stream which is usually covered by C. esculenta (Araceae) . The new species coexists with I. bannaensis in Loei Province.

Distribution. Thailand (Loei) ( Fig. 17 ).

Remarks. The new species can be distinguished from I. bannaensis as well as the other two Indosialis species by the following characteristics: 1) head and pronotum brown (orange in I. bannaensis and other species); 2) apical tooth of right mandible in male sharply produced (obtusely prominent in I. bannaensis ); 3) inner margin of left mandible in male without short setae (with small setae in I. bannaensis ); 4) presence of large sac-like structure in male genitalia (indistinct or absent in I. bannaensis and other species); 5) male gonocoxite 9 in lateral view with posterodorsal corner slightly produced (male gonocoxite 9 in lateral view with apex distinctly narrowed and curved dorsad in I. bannaensis ); 6) male gonostyli 11 relatively stout (much more slender in I. bannaensis ); 7) male ectoprocts not distinctly narrowed distad and incurved (male ectoprocts distinctly narrowed distad and incurved in I. bannaensis and other species) ( Fig. 15 ).

Figures

FIGURE 10. Indosialis siamensis sp. nov. (Holotype, THNHM-I-16801), male, A, B. dorsal view; C. lateral view. Scale bars: 5.00 mm.

FIGURE 11. Indosialis siamensis sp. nov. (paratype), female in lateral view. Scale bar: 5.00 mm.

FIGURE 12. Indosialis siamensis sp. nov., dorsal view. A. left mandible of male; B. right mandible of male; C. right mandible of female. Scale bar: 0.20 mm.

FIGURE 13. Indosialis siamensis sp. nov., male genitalia (paratype), A. dorsal view; B. ventral view; C. lateral view; D. caudal view. Sac.: sac-like structure. Scale bar: 0.20 mm.

FIGURE 14. Indosialis siamensis sp. nov., female abdominal apex (paratype), A. ventral view; B. gonapophysis 8, ventral view; C. lateral view. Scale bar: 0.50 mm (A, C); 0.25 mm (B).

FIGURE 15. Indosialis spp. Indosialis siamensis sp. nov. (A, C, E, G); Indosialis bannaensis (B, D, F, H). A, B. dorsal view; C, D. ventral view; E, F. lateral view; G, H. caudal view. Scale bar: 0.20 mm (A, C, E, G); 0.50 mm (B, D, F, H).

FIGURE 16. Molecular species delimitation of Sialidae using maximum likelihood (ML) and neighbor-joining (NJ) using partial COI sequences. Tree was inferred from 472 base pair of 19 species of Sialidae and a species of Corydalidae as the outgroup. Nodal support values are bootstrap values (percentage of 1000 replicate, left: ML; Right: NJ). Only nodes with bootstrap> 50% are indicated. Scale bar indicates 0.05 nucleotide substitutions. M: male adult; F: female adult; P: pupa; L: larva.

FIGURE 17. The map shows the geographical distribution of two Indochina Indosialis species. Indosialis bannaensis Liu, Yang & Hayashi, 2006 (●); Indosialis siamensis sp. nov. (■). The records from Phitsanulok, Kalasin Provinces (Thailand) are from Bowles & Contreras-Ramos 2016 and China and Vietnam (Liu et al. 2008).