Rhyacophila langkawia, Ivanov, Vladimir D. & Melnitsky, Stanislav I., 2013

Ivanov, Vladimir D. & Melnitsky, Stanislav I., 2013, New data on Rhyacophila (Trichoptera: Rhyacophilidae) from West Malaysia and Indonesia (Lombok and Bali) with descriptions of two new species, Zootaxa 3635 (4), pp. 476-484 : 479-480

Rhyacophila langkawia , new species

Fig. 3

Holotype. Male forewing average length 7.2 mm (n=7), body length 6.6 mm (n=7). Head light brown; abdomen, thorax and legs yellowish. Wings dark brown, with lighter speckles at basal anterior part of each forewing. Long projection from each pheromone gland on abdominal segment V. Abdomen with stout, short, sharp sternal process on segment VII in both sexes.

Male genitalia ( Fig. 3 ). Segment IX with narrow lateral parts having sinuous anterior and posterior margins and elongate posterodorsal and posteroventral parts; its posterolateral margins concave dorsally and convex ventrally; posterior margin incised medially in dorsal view. Preanal appendages fused with segment X, making complex structure with pair of compressed, membranous, ventral parts and longer, sclerotized, dorsal part consisting of two pairs of processses; two dorsolateral processes of this dorsal part (probable preanal appendages) gradually curved downward, truncate and possessing small teeth apically; two ventromedial processes of this dorsal part gradually curved upward, rounded apically. Proximal segment of each inferior appendage (gonocoxite) long with enlarged basal half in lateral and ventral views. Distal segment of each inferior appendage (gonostyle) semicircular and concave mesally in caudal view, 1/4th as long as gonocoxite, with attenuated apicoventroal angle. Phallic structures: Phallobase fused with aedeagus, resulting in single long structure; its apical part obliquely truncate in lateral view; ventral acute projection of aedeagus with faint subapicolateral ridges; parameres sclerotized, very slender, acute, and slightly shorter than phallic structure.

Diagnosis. This species is also in the R. curvata Group and closely resembles Rhyacophila tantichodoki Malicky & Chantaromongkol 1993 from South Thailand, but differs from it in the structure of male genitalia. Rhyacophila langkawia has a uniformly straight phallic structure, but in R. tantichdoki its apex is curved upwards so that the parameres are longer than the aedeagus in R. tantichodoki and shorter in R. langkawia . The ventral part of segment IX is longer in R. langkawia , making an apparent ventral projection of the segment; this projection changes the orientation of the inferior appendages, turning them upwards when at rest in R. langkawia , and the shorter sternal part of segment IX in R. tantichodoki results in a more nearly horizontal position of the inferior appendages. The dorsolateral processes of the dorsal part of segment X are nearly straight, separated basally, and truncate with small teeth apically and ventromedial processes are well developed in R. langkawia , whereas in R. tantichodoki the dorsolateral processes are slightly curved inwards, acute, not separated basally and have no teeth apically, and the ventromedial processes are not well developed.

Holotype male: Malaysia, Kedah, NW part of Langkawi, Temurun waterfall, 06º 26' 06" N, 99º 42' 30" E, h= 60 m, 29 January 2011, at light, leg. Melnitsky.

Paratypes: Same data as holotype except leg. Ivanov, 6 males with 7 females possibly of this species.

Distribution. West Malaysia (Kedah).

Etymology. The species name is derived from the name of its homeland island Langkawi.

Biology. Rhyacophila langkawia has been found in a single locality ( Fig. 4 B) of 6 collecting sites in Langkawi, so we suppose that it occurs very locally. It was sampled in the canyon approximately 50 m downstream of the largest waterfall of the island. The adults were found in a few light traps and apparently were absent in the close proximity of the waterfall. The stream has variable strength depending on the rainfalls; in the moment of collecting it had rather low water level and slow current speed because of the dry season. The stream waters were transparent and clean, with temperatures lower than those in the nearby streams.

Figures

FIGURE 4. Characteristic biotopes for Rhyacophila schmidirossia, new species (4 A) and Rhyacophila langkawia, new species (4 B). 4 A, Malaysia, Pahang, Cameron Highlands, small left tributary brook of River Barum (2 km SW Brinchang), 4 February 2011; 4 B, Malaysia, Kedah, NW part of Langkawi, near Temurun waterfall, 28 January 2011.

FIGURE 3 A – D. Rhyacophila langkawia, new species, male terminalia. 3 A, abdominal segments IX and X, left inferior appendage, and phallus apex, left lateral; 3 B, abdominal segments IX and X and inferior appendages, dorsal; 3 C, abdominal segments IX and X, inferior appendages, and phallus apex, ventral; 3 D, phallic structures, dorsal.