Rhagophthalmus nanus, Packova & Kundrata, 2023

Packova, Gabriela & Kundrata, Robin, 2023, A new species of Rhagophthalmus Motschulsky, 1854 (Coleoptera, Rhagophthalmidae) from Laos represents the smallest known member of the genus, ZooKeys 1184, pp. 81-89 : 81

Rhagophthalmus nanus sp. nov.

Figs 1 , 2 , 3

Type material.

Holotype, male, "Laos-NE, Houa Phan prov., 20°13'09-19"N, 103°59'54"-104°00'03"E, 1480-1510 m, Phou Pane Mt., 22.iv.-14.v.2008, Vít. Kubáň leg." (NMPC).

Type locality.

Laos: Houaphanh [Houa Phan] prov., Phou Pan-Gnai [Phou Pane] Mountain.

Diagnosis and comparison.

Rhagophthalmus nanus sp. nov. represents by far the smallest known species in Rhagophthalmus and can be easily recognized based on the following combination of characters: body small (3.50 mm), elongate, 3.50 times as long as wide; pronotum darker than elytra; elytra elongate, both combined 2.55 times as long as wide and 4.55 times as long as pronotum; aedeagus with parameres slightly longer than median lobe, and with phallobase about 1.35 times as long as wide, ventrally partly covering parameres, and with its anterior margin medially deeply emarginate. Two relatively small Rhagophthalmus species in the region, i.e., R. minutus Kawashima & Satô, 2001 (Thailand) and R. tonkineus Fairmaire, 1889 (Vietnam, China,?Laos), are still larger than R. nanus sp. nov., with the body length of 5.80 mm or more. Additionally, R. minutus is much darker, having the pronotum blackish and elytra dark brown (pronotum generally reddish dark brown and elytra light brown to brown in R. nanus sp. nov.), and the aedeagus with a median lobe distinctly longer than parameres and a phallobase relatively shorter, about 1.20 times as long as wide, not covering the significant portion of parameres in ventral view, and with its anterior margin rounded. Rhagophthalmus tonkineus has both the pronotum and elytra of roughly similar dark brown coloration, and the median lobe of the aedeagus distinctly longer than parameres. Another species from Laos, R. laosensis Pic, 1917, is much larger (9.00 mm), has relatively shorter and wider elytra (about twice as long as wide), and the median lobe of aedeagus distinctly longer than parameres.

Description.

Body (Fig. 1A-D ) 3.50 times as long as wide (3.50 mm long, 1.00 mm wide at humeri); light brown to brown, with head mostly black; pronotum medially reddish dark brown to blackish, with edges lighter, reddish brown; body surface covered with short light brown setae.

Head (Fig. 2A-C ) including eyes 1.25 times as wide as pronotum, with short semi-erect setae; area between eyes with surface smooth, shallowly depressed, very sparsely and finely punctate; area in between upper and lower portion of eye sparsely and coarsely punctate. Eyes large, their frontal distance 0.40 times eye diameter, laterally divided into a smaller upper portion and a larger lower portion (Fig. 2B ); eyes ventrally contiguous (Fig. 2C ). Mouthparts rather small, labrum transverse, partially membranous. Mandibles rather small, narrow, unidentate, sickle-shaped, strongly curved; basally covered with long setae, apical part bare. Maxillary palpi short, 4-segmented, basal palpomere shorter than wide, transverse, palpomere 2 slightly longer than wide; palpomere 3 short, distinctly transverse; ultimate palpomere longest, about twice as long as wide, apically pointed. Labial palpus minute, 3-segmented; palpomere 2 transverse, shorter than basal palpomere; ultimate palpomere similar in shape to ultimate maxillary palpomere, longer than wide, apically pointed. Antenna (Fig. 2A-C ) minute, short, surpassing anterior margin of pronotum (when positioned backwards), very slightly serrate, with 12 antennomeres (right antenna without ultimate antennomere); scape and pedicel robust, each slightly longer than wide, pedicel slightly longer than scape; flagellum (antennomeres 3-12) distinctly narrower than scape and pedicel; antennomere 3 longest, distinctly elongate, gradually widened toward apex; antennomeres 4-11 relatively short and subequal in length; antennomere 12 longer than wide, distinctly narrowed apically.

Pronotum (Fig. 2D ) transverse (0.55 mm long, 0.70 mm wide), about 1.30 times wider than long when width measured anteriorly (pronotum is widest posteriorly but since both posterolateral portions of pronotum are shriveled, the real shape of pronotum cannot be observed), slightly convex, widest at about posterior angles (pronotum shrunken in dry condition, giving the false appearance that it is widest anteriorly). Anterior margin widely rounded; lateral margins slightly rounded, posterior margin almost straight. Anterior angles inconspicuous; posterior angles short, apically rounded. Lateral pronotal carina complete. Surface of disc relatively smooth, sparsely covered with fine punctures and semi-erect setae, which are slightly longer than those on head and elytra. Prosternum distinctly transverse, with prosternal process reduced to short median protrusion. Scutellar shield (Fig. 2D ) tongue-shaped, almost twice as long as wide; sides shallowly and widely emarginate, apex widely rounded; sparsely covered with fine punctures and short semi-erect setae. Mesoventrite short, with median depression. Metaventrite with distinct long discrimen. Elytra (Fig. 1A-C ) elongate, subparallel-sided (2.55 mm long, 1.00 mm wide at humeri), both combined 2.55 times as long as wide, 4.55 times as long as pronotum, with apices strengthened, separately rounded, surface rather rough and sparsely covered with short, sub-erect setae. Leg (Fig. 1D ) slender; coxa elongate; femur elongate, flattened, obliquely attached to trochanter, distinctly wider than tibia; tibia shorter than femur, gradually slightly narrowed towards apex, apical tibial spurs short and thin; tarsus slender, simple, relatively long, subequal in length to tibia; pro- and mesotarsomeres 1 and 2 subequal in length, metatarsomere 1 longer than metatarsomere 2; in all legs tarsomere 3 shorter than respective tarsomere 2, tarsomere 4 shortest and tarsomere 5 distinctly longest; claw simple, slightly curved.

Abdomen (Figs 2F , 3A, B ) soft, tergites and sternites connected with extensive membranes, very sparsely and finely punctate, with sparse short setae, all tergites except the last one and all ventrites except the last one about subequal in length; tergite X (Fig. 3A, B ) free, elongate, narrowed, conical; sternite IX (i.e., last ventrite; Fig. 3C ) elongate, about 2.5 times as long as wide, basally narrowed, apically widened and very slightly emarginate. Male genitalia (Fig. 3D-F ) about 1.80 times as long as maximum phallobase width; median lobe relatively short, 2.50 times as its maximum width at base, widest at base, abruptly narrowed near middle, then subparallel-sided towards apex, apically rounded, basal struts relatively long, slender and divergent; parameres slightly longer than median lobe, curved, basally joint, medially with short tooth, apically narrowed and sharp; phallobase U-shaped, partly covering parameres in ventral view, about 1.35 times as long as wide and about 1.40 times as long as median lobe, anterior part medially gradually and relatively deeply emarginate, posteriorly slightly narrowed and rounded.

Female and immature stages unknown.

Etymology.

The specific epithet “nanus” refers to the small size of this species.

Distribution.

Laos (Houaphanh Province).

Figures

Figure 1. Rhagophthalmus nanus sp. nov., holotype, male A habitus, dorsal view B habitus, dorsolateral view C habitus, lateral view D habitus, ventral view. Scale bars: 1.0 mm (A-D).

Figure 2. Rhagophthalmus nanus sp. nov., holotype, male A head, frontal view B head, lateral view C head, ventral view D pronotum, dorsal view E thorax, ventral view F abdomen, lateral view. Scale bars: 0.2 mm (A-F).

Figure 3. Rhagophthalmus nanus sp. nov., holotype, male A abdomen, lateral view B apex of abdomen, lateral view C sternite IX, dorsal view D male genitalia, dorsal view E male genitalia, lateral view F male genitalia, ventral view. Scale bars: 2.0 mm (A); 0.5 mm (B); 0.2 mm (C-F).