Macrostemum siemreapensis Laudee & Malicky, 2020

Laudee, Pongsak, Kong, Chamroeun & Malicky, Hans, 2020, New species of caddisflies (Trichoptera: Psychomyiidae, Hydropsychidae Leptoceridae) from Mekong tributaries, Cambodia, Zootaxa 4853 (1), pp. 133-138 : 135-136

Macrostemum siemreapensis Laudee & Malicky n. sp.

Figs 2 A–2G

Type material. Holotype male ( PSUNHM). Cambodia: Siem Reap Province, Siem Reap River , 13°24’09”N, 103°52’48”E, ca. 22 m a.s.l., 6.v.2019, leg. Pongsak Laudee.

Paratypes. Same data as holotype, 1 male ( PSUNHM), 1 male ( CHM) .

Etymology. The species is named for the type locality, Siem Reap Province.

Description. Length of each male forewing 8.0–10.0 mm (n = 3); Head and thorax dark brown dorsally. Each antenna with scapus and pedicellus light brown, some adjacent segments of antenna dark brown, remaining antennal segments pale yellow. Coxae of forelegs brown, distal ends of tibiae and claws brownish, remaining parts of legs yellow. Abdomen brown dorsally, yellow ventrally except sternum VIII brown. Forewings dark brown with yellowish white pattern same as in M. fenestratum Albarda 1887 (e.g., Malicky 2010, page 189)

Male genitalia ( Figs 2 A–2F). In dorsal view ( Fig. 2A ), segment IX rectangular with rectangular incision for half of its length anteriorly; posterolateral lobes of segment IX triangular; in lateral view ( Fig. 2B ), ventral 3/4 of segment IX oval with irregularly convex anterolateral margins and rounded posterolateral lobes, apicolateral margins with numerous setae; in ventral view ( Fig. 2C ), segment IX dumbbell-shaped. Segment X in dorsal view ( Fig. 2A ), long, with parallel-margined incision nearly as deep as pair of resulting trapezoidal lobes; in lateral view ( Fig. 2B ) somewhat triangular and slightly longer than basal segments of inferior appendages. Inferior appendages tubular, long; each with basal segment tubular, about 1.2 times as long as apical segment; apical segment (harpago) tubular, with round apex; curving slightly mesad in ventral view ( Fig. 2C ). Phallus axe-shaped, broadest basally, bulbous subapically with protruding structure apicodorsally in lateral view ( Fig. 2D ); bulbous subapical part of phallus with knot-like apex in ventral view ( Fig. 2E ) and with looped structure in dorsal view ( Fig. 2F ).

Diagnosis. The new species is very similar to M. fenestratum and M. dion Malicky and Chantaramongkol 1998 (in Malicky 1998), all three of which have forewings dark brown with a pale yellowish pattern. However, the dorsal apex of the phallus of the new species has no curved hooklet but instead a knot-like protruding structure in ventral view and a looped structure in dorsal view. Macrostemum seba Malicky & Prommi 2009 (in Malicky 2009) is also very similar to the new species, but the phallus of that species has no protruding structure.

Figures

FIGURES 2A–2F. Male genitalia of Macrostemum siemseapensis n. sp. 2A, dorsal; 2B, left lateral; 2C, ventral; 2D, phallus, with apex enlarged in inset, left lateral; 2E, phallus apex, ventral; 2F, phallus apex, dorsal. Seg IX = segment IX, Seg X = segment X, Inf = inferior appendage (paired).