Rismethus jiangi Qiu, 2025, sp. nov.
Creators: name: Qiu, Lu
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Elateridae
Rismethus
Rismethus jiangi

description: Rismethus jiangi sp. nov.
Chinese common name: 姜ĸāḃ叩ş
(Figs 1–4)
Type locality. near Sanbanqiao, Xijingshan Mountain, Lin’an District, Hangzhou City, Zhejiang Province, 115m.
Type material. Holotype: male (MYNU), near Sanbanqiao [三Dzñ], Xijingshan Mountain [ƱKƜ], Lin’an District [临 Ṙ 区], Hangzhou City [ṻṅṪ], Zhejiang Province, 115m, 119.7278E, 30.2791N, 1.I.2025, Ding-Lei Jiang leg. Paratypes: 5 males and 2 females (MYNU), same data as holotype; 1 male (AHNU), Shitan Village [ƋDZť], Xiakeng Town [Ḇ坑º], Shexian County [Ü县], Huangshan City [WƜ Ṫ], Anhui Province, 251m, 118.6698E, 29.9324N, 17.VII.2024, Rui-E Nie & Hai-Zhou Xu leg.
Diagnosis. Head and scutellar shield dark brown, elytra dark brown with basal fourth reddish-brown, sometimes apical half with two reddish-brown spots (Fig. 1A, D). Ventral side reddish-brown, abdomen slightly darker (Fig. 1B). Pronotum uniformly covered with two types of scales (Fig. 2G). Hind angle with three teeth, with middle one distinctly larger (Fig. 2A–B). Metacoxal plate with quadrate angle at widest part. Hind wings absent.
Comparison. This new species is morphologically similar to R. ryukyuensis Ôhira, 1999, based on its general body proportions and the absence of hind wings (Suzuki, 2019). However, it clearly differs from R. ryukyuensis by lighter coloration (reddish-brown), with dark brown head and scutellar shield, and bicolor elytra. In contrast, R. ryukyuensis has a predominantly dark brown body, with light brown antennae, legs, basal portion of the elytra, and hind angles of the pronotum. In the three teeth of the hind angle of pronotum, R. jiangi sp. nov. has more prominent middle one (Fig. 2A–B), whereas in R. ryukyuensis it is short and blunt (Ôhira, 1999, fig. 1H). The metacoxal plate differs in shape between the two species, with the widest part of R. jiangi sp. nov. being more acute than that of R. ryukyuensis (Fig. 2H; Ôhira, 1999, fig. 1B).
Description. Male (holotype) (Fig. 1A–C; 2; 3A–C). Length 2.4 mm, width 0.9 mm, antennal length 0.7 mm, pronotum length × width = 0.8 × 0.9 mm, elytral length 1.3 mm. Body bicolor (Fig. 1A–C), reddish-brown overall, abdomen slightly darker; head and scutellar shield dark brown; pronotum slightly darkened medially at base. Elytra dark brown, basal fourth reddish-brown, apical half with two large reddish-brown spots. Legs yellowish brown.
Body densely covered with two types of yellow scales (Fig. 1A–C; 2A–C, F–H): large, flat, drop-like scales and fine, narrow, needle-like scales, both curved and semi-erected. Dorsally, drop-like and needle-like scales evenly distributed, directed forward and outward on head and pronotum. Scape with only needle-like scales on inner sides. Elytra with drop-like scales forming regular vertical lines between puncture striae, directed posteriorly. Basal margin of elytra and base of scutellar shield with additional drop-like scales. Ventral side with smaller drop-like and needle-like scales compared to dorsal side. Hypomeron, prosternum, metanotum, and metacoxal plates mainly covered with drop-like scales, interspersed with a few needle-like scales. Mesonotum and mesocoxa covered with needle-like scales. Legs covered with both types of scales, tibiae primarily with drop-like scales along outer margins. Abdomen with needle-like scales at base, transitioning to drop-like scales toward apex. Hypomeron base and its tarsal reception, as well as mesanepisternum without scales. Elytral epipleuron with sparse scales of both types.
Head almost flat (Fig. 2A). Punctures large, umbilicate; intervals smooth, subequal to or smaller than puncture diameter. Antennae short, reaching beyond middle of pronotum, serrate from antennomere 4 (Fig. 1A–B; 2D). Antennomere 1 robust, long; antennomere 2 cylindrical, base constricted; antennomere 3 cylindrical, slightly longer than half length of antennomere 2; antennomeres 4 to 10 similar in length, slightly longer than antennomere 3, all wider than long; apices of serrated portions of antennomeres 4 to 10 narrowed, similar but somewhat variable in shape; last antennomere ovate, apical portion obliquely truncated, forming tapered apex. Eyes small, sheltered by anterior angles of pronotum. Apical segment of maxillary palpus oval, apex tapered.
Pronotum with disc convex, almost as wide as elytra, slightly longer than wide, widest near middle (Fig. 2A). Lateral carina serrated (Fig. 2B). Side narrowed toward anterior angle sharply. In dorsal view, anterior angle sharp, while in lateral view rounded apically. Lateral margins near middle arched, then weakly narrowed before hind angles. Hind angles of pronotum short, formed by three small teeth (Fig. 2B). Middle tooth more protruded and pointed than lateral two. Punctures large, umbilicate, evenly distributed, intervals between punctures smooth, slightly greater or subequal to diameter of one puncture.
Prosternum quadrate, widest at base of chin-piece, slightly narrowed towards base (Fig. 2F). Prosternal sutures deeply grooved apically. Prosternal lobe broad, anterior margin nearly straight. Prosternal process in lateral view straight, stick-like, with subapical emargination in dorsal part, apex blunt, lateral sides carinated (Fig. 2E). Size and density of prosternal punctures similar to those on pronotum, intervals smooth. Hypomeron with thickened, course basal margins, unevenly serrated; antennal groove extending not beyond anterior half of hypomeron; punctures oval, intervals on average subequal to diameter of one puncture; tarsal reception with smaller punctures; basal portion of hypomeron with surface shagreen without punctures.
Mesoventrite with anterior margin dentate, punctures small, sparsely distributed around mesoventral cavity and mesocoxa; mesanepisternum without punctures. Metavenrite with slightly larger punctures than prosternum; tarsal reception formed by oblique carination from mesocoxa to outer end of metacoxal plate (Fig. 2F). Metacoxal plates widened from inner base to lateral portion, widest at middle, then suddenly narrowed along lateral half, forming quadrate angle at widest part; punctures similar to those in Metavenrite (Fig. 2H). Legs short, tarsi simple, similar, slightly shortened from 1 to 4. Tarsus 5 approximately twice length of tarsus 4. Scutellar shield smooth, minorly wider than long, basal portion elevated, forming angle at middle, posterior margin straight (Fig. 2A).
Elytra arched, 1.4 times longer than wide, 1.6 times longer than pronotum, almost as wide as pronotum (Fig. 1A). Elytral epipleuron extended to 1/3 of elytral length at basal half (Fig. 1C). Lateral margin serrated in basal 1/3 (Fig. 1A; 2C). Smooth in remaining part. Sides arched, forming obtuse angle at basal 1/3. Distal part with sides arched and narrowed toward apices, each apex rounded. Shoulders slightly serrated. Striae formed by regular large round punctures similar to those on pronotum, intervals subequal to three puncture diameters. Interstriae smooth, each with line of smaller punctures than stria. intervals subequal to 4–5 diameters of one puncture. Wings absent.
Punctures of abdomen similar to those on Metavenrite. Large, evenly distributed, with intervals subequal to or larger than one puncture diameter. Apical sternite rounded at apex. Tergite VIII semi-oval, wider than long (Fig. 3A); tergite IX with apical margin widely and roundly concave (Fig. 3B); tergite X large, apical portion roundly protruded (Fig. 3B). Sternite IX stout, 2.7 time longer than wide, apical portion rounded.
Aedeagus with median lobe slightly surpassing paramere, apex blunt; parameres with curved hook. Phallobase narrowed, median V-shaped (Fig. 3C).
Paratype males. Body length 2.1–2.4 mm, similar to holotype male; some individuals with lighter color in dark portions of head and elytra, elytral spots may be indistinct.
Paratype females. Body lenth 2.1–2.3 mm, similar to males; some individual with lighter head and elytra (Fig. 1D), no distinct sexual dimorphism in other respects. Tergite VIII with apex pointed, lateral sides subparallel basally; sternite VIII with tapered apex, spiculum ventrale 5 times longer than sternite VIII length (Fig. 3D). Ovipositor short, coxite about 1/3 of total length, sides setose, styli tiny, attached subapically (Fig. 3E). Bursa copulatrix without sclerotized structure.
Larva. Unknown.
Distribution. China: Zhejiang and Anhui (Fig. 4C).
Bionomics. Found in low mountainous areas in Zhejiang and Anhui, East China. Individuals from Zhejiang were found under stones at the roadside during winter (Fig. 4A–B).
Etymology. This new species is named after the collector, Mr. Ding-Lei Jiang [姜丁ª].
description: Published as part of Qiu, Lu, 2025, Description of a new flightless species of Rismethus Fleutiaux from China (Coleoptera: Elateridae: Agrypninae), pp. 430-436 in Zootaxa 5609 (3) on pages 431-434, DOI: 10.11646/zootaxa.5609.3.8, http://zenodo.org/record/15215336