New species of caddisflies (Trichoptera, Ecnomidae, Polycentropodidae, Psychomyiidae) from Mekong tributaries, Laos

Abstract Four new species of caddisflies are added to the fauna of Mekong River, Laos. Described and illustrated are Ecnomus petchanaaesp. nov. and E. boonsawaengaesp. nov. (Ecnomidae), Polyplectropus proukaewisp. nov. (Polycentropodidae), and Psychomyia srichanaisp. nov. (Psychomyiidae) from tributaries of the Mekong River, Laos. Ecnomus petchanaaesp. nov. can be distinguished by the characters of the superior appendages, which are slender and club-shaped in lateral view. In E. boonsawaengaesp. nov., the inferior appendages are tubular with a concave incision subapically and truncated apex. Polyplectropus proukaewisp. nov. has the distal process of the dorsal branch of the inferior appendage close to the base of the inferior appendages and the length of the process is half of inferior appendages. Psychomyia srichanaisp. nov. can be distinguished by the structure of the dorsal branches of the harpagones and apical sclerite. The outer branches of the harpago in the latter species are bifurcated and bent 90° degrees outward, and the inner dorsal branches of harpago are curved outward. The apical sclerite is indiscernible.


introduction
The Mekong River, with a length of 5,400 km is the 12 th longest river in the world and passes through six countries, originating from China, through Myanmar, Laos, Thailand, Laos, Cambodia, and finally Vietnam (Mekong River Commission 2010a, 2010b. Its river basin is among the most diverse riverine systems of the world, where 367 new species were recently found, including 24 new species of fish and 21 new species of amphibians (World Wild Fund 2014). The Mekong River is in the Oriental Region where diversity of Trichoptera is gener ally high (de Moor and Ivanov 2008), however, so far this aquatic insect order has not been intensively studied along its course.
Considering the overall diversity of the Mekong River and its tributaries and the under-investigated caddisfly fauna of this region, many new species records and descriptions are expected. This article adds four new species from the Mekong River and its tributaries to the list of Trichoptera in Laos.

Materials and methods
Adult caddisfly specimens were collected with a UV pan light trap (12 V, 10 W) operated along streams and the river overnight at the locations indicated below. Collected specimens were preserved in 70% ethanol, and caddisflies were later manually sorted from other insects. For species-level identifications, the male genitalia were observed under a stereomicroscope. For this purpose, the male genitalia from a specimen from each new species were dissected out. Muscle tissue was macerated by heating in 10% KOH at 60 °C for 30-60 minutes and then soaking in a detergent solution. Drawings were initially made in pencil using a compound microscope equipped with a drawing tube and used to produce the final vector graphics in Adobe Illustrator software.
Holotypes and paratypes are stored in 70% ethanol and deposited in Princess Maha Chakri Sirindhorn Natural History Museum, Prince of Songkla University, Hat Yai Campus, Hat Yai District, Songkhla Province, Thailand (PSUNHM). Some paratypes are deposited in the collection of Hans Malicky (CHM), the Clemson University Arthropod Collection (CUAC), and the National Museum, Prague, Czech Republic (NMPC). Terminology for genitalic structures for different genera follows that of Cartwright (1994) for the genus Ecnomus, Schmid (1997) for the genus Psychomyia and Chamorro and Holzenthal (2011) for the genus Polyplectropus. Diagnosis. The male genitalia of E. petchanaae sp. nov. are similar to Ecnomus gapit Cartwright, 1994, E. yuleae Cartwright, 1994, E. dares Malicky, 2000, and E. perseis Malicky, 2008 described from Borneo. The superior appendages of all these species, including the new species, are particularly large and the subapical part of the superior appendages is covered by numerous spiny setae. However, E. petchanaae sp. nov. can be distinguished by the shape of its superior appendages, which, in lateral view, are slender and club-shaped, but basally broad in E. gapit, E. yuleae, E. dares, and E. perseis. In addition, in ventral view of the outer surface of the inferior appendages of the new species is crescent-shaped, whereas they are curved and claw-shaped in E. gapit, E. yuleae, E. dares, and E. perseis.
Description. Adult, male, length of each male forewing 5.6-6.0 mm; color in alcohol of head, thorax, forewings, abdomen, and legs brown. Male genitalia as in Figure 1A-D. Tergum IX somewhat square, anterior margin truncated, posterior margin bilobed in dorsal view (Fig. 1A); trapezoid and rounded anterodorsally in lateral view (Fig. 1B). Sternum IX ovoid in lateral view (Fig. 1B); rectangular with ¼ concave incision posteriorly, bilobed and rounded anteriorly in ventral view (Fig. 1C). Superior appendages long, slender, with expanded base, curved inward posteriorly with numerous long spiny setae subapically in dorsal view ( Fig 1A); in lateral view, superior appendages, relatively large, long, slightly curved upward, bulb-like apically, with numerous spiny setae (Fig. 1B). Inferior appendages tubular, bent inward, beak-like apically in lateral view (Fig. 1B); in ventral view, crescent-shaped, with a submediate knot, overlapping each other subapically (Fig. 1C). Phallus long, tubular, curved upward, pointed apex with dorsal process in lateral view (Fig. 1B); in ventral view, bulb-like, with pointed apex (Fig. 1D). Diagnosis. The male genitalia of E. boonsawaengae sp. nov. are similar to E. aktaion Chantaramongkol, 1997 andE. uttu Malicky &Chantaramongkol, 1993. In these species, the superior appendages are particularly long and slender with a basoventral process on the superior appendage. However, E. boonsawaengae sp. nov. can be easily distinguished by the shape of the inferior appendages. In lateral view, the inferior appendages are tubular with a subapical concave incision and truncated apex in E. boonsawaengae sp. nov., but in E. aktaion and E. uttu the inferior appendages are somewhat triangular and trapezoidal, respectively, and with a pointed apex. In addition, each inferior appendage in E. boonsawaengae sp. nov. has a process, in ventral view, which is lacking in E. aktaion and E. uttu.
Description. Adult, male, length of each male forewing 4.0 mm; color in alcohol of head, thorax, forewings, abdomen, and legs grayish brown. Male genitalia as in Figure 2A-D. Tergum IX in dorsal view bilobed posteriorly, U-shaped ½ incision anteriorly (Fig 2A); in lateral view, tergum IX narrow, expanded dorsally (Fig. 2B). Superior appendages tubular, base with lateral lobe, slightly bent apically to form beaklike apex in dorsal view (Fig 2A); in lateral view, tubular, truncated apically (Fig. 2B). Basoventral projection of superior appendage tubular with setae apically in lateral view. Sternum IX in lateral view chicken-drumstick-like and rounded apically (Fig. 2B); in ventral view, trapezoid, slightly expanded apically, with shallow U-shaped incision anteriorly and shallow V-shaped incision posteriorly (Fig. 2C). In lateral view, the inferior appendages tubular, with concave incision subapically, truncated apex ( Fig 2B); in ventral view, claw-like, with process basodorsally (Fig. 2C). Phallus sickle-like, with lobe mesodosally in lateral view (Fig. 2D). Diagnosis. The male genitalia of P. proukaewi sp. nov. are similar to those of P. daimong Oláh & Johanson, 2010 from Vietnam. In both species, the dorsal branch of the inferior appendages forms a hooked-like process. However, P. proukaewi sp. nov. can be distinguished by the considerably shorter distance of the distal processes of the dorsal branch of the inferior appendages to their bases compared to P. daimong, in which this distance is considerably longer. Additionally, in the new species, the length of the distal processes in lateral view equals half of the length of inferior appendages, whereas the length of the distal processes equals the length of inferior appendages in P. daimong.
Etymology. The species epithet honors Dr Nitat Proukaew, Assistant Professor in the Faculty of Science and Industrial Technology, Prince of Songkla University, Surat Thani Campus.

Discussion
Ecnomus petchanaae sp. nov., E. boonsawaengae sp. nov. and P. proukaewi sp. nov. were collected from a stream and waterfall on Bolaven Plateau, southern Laos. Here, forest type is montane evergreen rainforest. The three new species are rhithral species, which live in small streams where the substrate is dominated by boulders and cobblestones ( Fig. 5A-C). Along with the eight previously recorded species of Ecnomus, there are now 10 species belonging to this genus are now known in Laos; of these, four species, including the new species, are apparently endemic to the country (Malicky 2010;Laudee and Malicky 2017). Ecnomus species not only occur in rhithron stream zones but also are found in potamon stream zones . Three species of Polyplectropus, including the new species, are now recorded from Laos. Among these, two species are reported only from Laos (Malicky 2010). Psychomyia srichanai sp. nov. was collected from main river channel of the Mekong River in Luang Prabang Province, northern Laos (Fig 5D). This is a potamon species that lives in main Mekong River. Psychomyia srichanai sp. nov. is in P. capillata species group according to the charecters of the group as diagnosed by Malicky and Chantaramongkol (1993). In total, eight species of Psychomyia have been reported from Laos, of which four species, including the new species, are reported only from Laos (Malicky 2010).