Echinoaesalus chungi Huang & Chen

Huang, Hao & Chen, Chang-Chin, 2015, Discovery of a second species of Aesalini from Taiwan, with description of the new species of the genus Echinoaesalus Zelenka, 1993 (Coleoptera: Lucanidae), Zootaxa 3920 (1), pp. 163-170 : 164-169

Echinoaesalus chungi Huang & Chen , new species

( Figs. 1–7, 10–13, 15, 19–21, 23–29, 36, 39)

Type material. Holotype ( Figs. 1–2, 6): TAIWAN: ♂, Pingtung County, Li-long-shan, 600–650m, 1.III.2014, Yi- Ting Chung leg. ( NMNST). Paratypes: TAIWAN: 17 ♂♂, 6 ♀♀, same data as for the holotype (3 ♂♂, 1 ♀ in CHH, 1 ♂ in BMNH, 13 ♂♂, 5 ♀♀ in CCCC); 17 ♂♂, 19 ♀♀, same locality as holotype, 25.XI.2014, Yi-Ting Chung, Chang-Chin Chen, & Bo-Xin Kuo leg. (all in CCCC).

Holotype description. Length of pronotum-elytra measured from apex of pronotum to the caudal end of elytra: 3.4 mm.

Ground color of the whole body on both surfaces dark reddish brown. Bristles on dorsal surface of the body dark brown. Bristles on ventral surface of the body bright yellow.

Head: Width approximately 0.45 times as wide as pronotum. Interocular width about 4 times as wide as eye. Anterior portion of head in front of eye nearly as long as eye. Intermandibular projection obtusely angled, not protruding. Canthus present, nearly even in width throughout, with end rounded and hardly beyond eye. Left mandible with a subapical dorsal tooth and a subapical ventral tooth. Right mandible with a subapical dorsal tooth but without ventral tooth. Both mandibles with mola well developed and massive in inner lateral view, and each with a setose prostheca along medial edge. Labrum setose, movable and nearly 1/3 times as wide as head. Galea of maxilla with setae on apex regularly curved and brush-like. Lacinia of maxilla free and large. Ligula bilobed and setose. Base of labial palpomere 1 concealed by mentum. Palp insertions on prementum separated by a distance equal to 3–4 times the width of first palp. Antenna partially geniculate and composed of ten antennomeres. Antennal scape without longitudinal groove. Antennal club composed of the last three antennomeres and completely pubescent. Antennomere 3 elongate, nearly twice as long as wide. Mentum transverse and rounded at lateral corners, setose near borders but glabrous in central area, microsculptured but without large punctures, and with a transversal central sulcus that is bent backwards at lateral ends (hooked laterally).

Thorax and abdomen: Ratio of pronotum-elytra-length to elytra-width: 1.46. Ratio of thickness to length of elytra: 0.66. Dorsal line of elytra in lateral view strongly and evenly convex. Pronotum and elytra densely punctate, with punctures irregularly distributed and not serially in longitudinal lines. Scutellum slightly longer than wide. Intercoxal process of prosternum plate-like, slightly convex in lateral view, with posterior margin almost as far as procoxae, without a step-like projection posteriorly. A pair of sublongitudinal cavities present just behind mesocoxae on metasternum. Metasternum and abdominal ventrites without long sulci. Posterior margin of the last visible abdominal ventrite rounded, but rather flat near center. Semicircular punctures along the anterior margin of the abdominal ventrites 3–5 transverse and markedly broader than those of the abdominal ventrites 1–2. Hindwing as in E. arayai Huang & Imura, 2011 : veins 3dA1 and 3dA2 clearly defined; vein 3dA2 not reaching the margin of wing; origin of vein 3dA1 close to base of vein 3dA2; vein 3dA1 nearly in parallel with vein 2dA3.

Surface structures: Vestiture of pronotum and elytra consisting of two types of elements: the stick-like bristles and the irregularly branched tomenta. Bristles longitudinally ribbed, inserted anteriorly in the wall of the punctures, sparsely distributed but placed serially in 11 longitudinal lines, erect and not forming clumps. Tomenta arising anteriorly in the wall of the punctures. All punctures with margins sharply defined, and with floor raised and polygonally sculptured. Puncture of bristle not associated with a tubercle outside of puncture.

Legs: Protibia markedly broadened from base to apex, with a minute inner terminal spur, an outer apical spine and 2 smaller spines on outer lateral margin, and with seta-tuft along the inner lateral margin near apex. Apical spine curved and nearly half as long as the width of protibia at apex. Mesotibia with 2–3 small spines. Metatibia smooth on outer lateral margin. All tarsi short, with the combined length about half as long as tibia.

Male genitalia (Figs. 36 – 41): 9th abdominal segment slender and elongate; basal lobe obsolete; paired pleurites plate-like and protruding ventrally; dorsal plate membranous. Basal piece short and small, not longer than parameres. Parameres nearly half as long as medial lobe of parameres. Medial lobe gently curved and gradually widened from base to apex in lateral view, contracted at middle but generally tuber-like in dorsal view, asymmetrical and not completely sclerotized at apex, with outer half of dorsal surface not pigmented, and with a long and twisted sclerite originating from ventral surface.

Description of male paratypes. Individual variation is only found in the color of the body on both surfaces and the length of canthus. There is no variation in the male genitalia.

Description of female paratypes. Sexual dimorphism in external morphology is very striking. Differences are found in the following characters. Head ( Fig. 4) about 0.40 times as wide as pronotum, thinner than in male ( Fig. 1). Labrum ( Fig. 14 ) nearly 1/5 times as wide as head, thinner than in male ( Fig. 13 ). Galea of maxilla ( Fig. 30) thinner than in male ( Fig. 27), with setae on apex not brush-like. Lacinia of maxilla free but smaller than in male. Ligula ( Fig. 29) obsolete and not large and bilobed as in male ( Fig. 26). Palp insertions on prementum separated by a distance equal to width of first palp ( Fig. 28). Mentum ( Figs. 16–17) thinner than in male ( Figs. 18–19) and more angled at anterior corners, with 3 well separated sulci instead of the transversal sulcus in male. Intercoxal process of prosternum ( Fig. 21) thinner than in male ( Fig. 20), with a markedly shorter anterior margin. Posterior margin of the last visible abdominal ventrite more arched near center than in male. Protibia ( Fig. 35) thinner than in male ( Fig. 34), with apical spine longer than half the width of protibia at apex. Last abdominal ventrite with a central projection on anterior margin, which is absent in male.

Female genitalia ( Fig. 51). Hemisternites well sclerotized and setose near rounded apex, with styli elongate, sclerotized, non-setose, and pointed outwards; bursal duct short and wide; bursa copulatrix shorter than in E. arayai ( Fig. 50); accessory gland originated near the entrance of bursa copulatrix; spermathecal duct slender and long, arising from the terminal end of bursa copulatrix; spermatheca small; spermathecal gland long and slender, not strongly demarcated from its duct; the combined length of spermathecal gland and its duct much greater than the length of the spermatheca.

Diagnosis. This new species is very similar to E. arayai from Borneo, but can be distinguished by the following combination of characters: 1) size of the entire body smaller ( Figs. 7–12 ); 2) elytra more elongate; 3) apical spine of protibia markedly longer in both sexes ( Figs. 31–35); 4) male mentum with laterally hooked sulcus ( Figs. 15, 18–19); 5) female mentum with only separated sulci instead of a transverse sulcus ( Figs. 16–17); 6) bristles inserted anteriorly in the wall of the punctures on dorsal surface of the body, not centrally as in E. arayai ; 7) bristles on elytra placed serially in 11 longitudinal lines, not irregularly as in E. arayai ; 8) 9th abdominal segment of male with relatively larger paired pleurites (Figs. 36, 42); 9) medial lobe of parameres with weakly pigmented dorsal surface on distal half (Figs. 40, 46) and with the pigmented distal sclerite interrupted on dorsal surface (Figs. 40, 46); 10) female genitalia with longer styli, thinner hemisternites and shorter bursa copulatrix ( Figs. 50–51).This new species undoubtedly belongs to the E. matsuii group ( Huang et al. 2011), with only the stick-like bristles and tomenta but devoid of the scale-like bristles on dorsal surface of the body. It closely resembles E. jaechi Zelenka, 1993 from Sulawesi in having the similar size of the entire body and the serially placed bristles on elytra, but can be distinguished from the latter by having punctures on the elytra not placed serially in longitudinal lines ( Figs. 1, 4) and the anterior margin of prosternal process not protruding in center ( Figs. 20–22).

This species is also similar to E. matsuii (Araya, 1993) from the Malay Peninsula, but can be distinguished from the latter by the following combination of characters: 1) elytra of both sexes more elongate than in E. matsuii ; 2) the pair of cavities on the metasternum just behind the mesocoxae almost longitudinal ( Figs. 2, 5), not so oblique as in E. matsuii ; 3) male canthus nearly even in width throughout, not widened toward the distal end as in E. matsuii ; 4) elytra of female evenly punctate everywhere, not so densely punctate around the sutural line as in E. matsuii ; 5) male mentum with a clearly marked transversal sulcus which is bent backward at lateral ends ( Figs. 18–19), female mentum with 3 well separated sulci ( Figs. 16–17), whereas in both sexes of E. matsuii such sulcus FIGURES 36–47. Male genitalia under same scale (scale bar 1 mm). 36–41— Echinoaesalus chungi , holotype; 42–47— Echinoaesalus arayai , paratype; 36, 42—9th abdominal segment in lateral view; 37, 43—9th abdominal segment in ventral view; 38, 44—medial lobe of parameres in ventral view, arrow directed to end of paramere; 39, 45—medial lobe of parameres in right lateral view, arrow directed to beginning of the weakly pigmented portion; 40, 46—medial lobe of parameres in dorsal view, arrow directed to beginning of the weakly pigmented portion, arrow also directed to the interrupted portion of distal sclerite in 40; 41, 47—medial lobe of parameres in left lateral view.

(sulci) replaced by some punctures on mentum “connected and indistinctly forming inverted V-shaped sulcus” (Araya 1993); 6) medial lobe of parameres more elongate and parameres relatively shorter than in E. matsuii ; 7) distal sclerite closer to the pigmented main part of medial lobe of parameres than in E. matsuii ; 8) dorsal surface of medial lobe of parameres well pigmented at basal half but clearly less pigmented at outer half, not evenly pigmented as in E. matsuii .

Further diagnosis between the new species and other Aesalini species can be found in the key.

Remarks. During the study of this new species, we became aware that all Echinoaesalus species might have strong sexual dimorphism in the galea of the maxilla, appearance of the ligula and distance of palp insertions on prementum. Such sexual dimorphism for the genus Echinoaesalus has never been noticed in all the previous publications ( Krikken 1975, 2008; Araya 1993; Araya et al. 1993, 1995; Zelenka 1993, 1994; Araya & Hamid, 1996; Huang et al. 2011; Huang & Chen 2013). We have examined the females of E. arayai and E. hidakai and confirmed our observation in E. chungi . The females of the Echinoaesalus species share the characters of maxilla, labium and ligula with the Himaloaesalus species ( Huang & Chen 2013), suggesting that the two genera are closely related phylogenetically.

Echinoaesalus chungi shows significant sexual dimorphism in the width of the head, size of the labrum, length of the apical spine of the protibia, size and shape of the mentum, appearance of sulci or sulcus on the mentum, and shape of the prosternal process. Such striking sexual dimorphism has never been found in the previously known species of Echinoaesalus .

It is difficult to infer the phylogenetic relationships between E. chungi and the other known species because most of the previously known species of Echinoaesalus are poorly described.

Type locality. Taiwan: Lilongshan, Pingtung County.

Etymology. This new species is named in honor of Mr. Yi-Ting Chung, who discovered this new species.

Figures

FIGURES 13 – 14. Echinoaesalus chungi, heads in full face under same scale (scale bar 1 mm). 13 — male paratype; 14 — female paratype. Arrows directed to the lateral ends of labrum.

FIGURES 7 – 12. Echinoaesalus species under same scale (scale bar 1 mm). 7 – 9 — Echinoaesalus chungi, paratypes; 10 – 12 — Echinoaesalus arayai, paratypes; 7 – 8, 10 – 12 — males; 9 — female.