Melalgus plesiobatillus Liu & Beaver, 2023

Liu, Lan-Yu & Beaver, Roger A., 2023, The first Asian species of Polycaon Castelnau, and a new montane species of Melalgus Dejean from China (Coleoptera: Bostrichidae: Polycaoninae), Zootaxa 5315 (3), pp. 271-281 : 275-277

Melalgus plesiobatillus Liu & Beaver , sp. n.

Fig. 2a, d‒e, g , Fig. 3a‒e

Type material. Holotype: Male: CHINA: Zhejiang, Gutianshan NNR, 118.14°E, 29.25°N, 903m, 2010, local collector. (Deposited in NME.)

Allotype: Female : CHINA: same data as holotype. (Deposited in NME.)

Paratypes: same data as holotype (1♀ IOZ, 1♁ 1♀ LYLC, 1♁ RABC) .

Male.

Body. 19‒20 mm in length (mean = 19.7mm, n = 3), 3.9‒4.4 times as long as wide. Head, thorax and abdomen reddish-brown, evenly arcuate, with recumbent yellowish pubescence, legs and antennae paler than body.

Head. Narrower than pronotum, shining, surface densely granulate, each rounded granule bearing an erect, fine hair-like seta; vertex weakly domed with granules concentrically arranged around summit; fronto-clypeal suture indicated only by an impressed line in middle; clypeus with anterior margin broadly emarginate, a distinct protruding tooth in middle; labrum densely punctured, shining, anterior margin strongly, broadly emarginate fringed with yellow-reddish pubescence; mandibles stout, asymmetrical, densely granulate dorso-laterally on either side of labrum. Gula without a ventral projection. Antennae with 11 antennomeres, first antennomere oblong, longer than second; funicle antennomeres short; last three antennomeres forming a loose club, the first two club antennomeres triangular, the last oval, each antennomere with two fine, longitudinal, canaliculate sensory areas on each side.

Pronotum. 1.05 times as wide as long, trapezoidal, narrower than base of elytra, widest in apical fourth, the sides weakly concave posteriorly, densely granulate except close to anterior margin where punctate, shallowly transversely impressed behind anterior margin at middle, median impressed line extending to middle of pronotum, deepened anteriorly, pubescence whitish, recumbent.

Scutellum. Visible part quadrate, rugose-punctate, punctures with short, fine, hair-like setae.

Elytra. 2.2 times longer than wide, wider than anterior margin of pronotum, parallel-sided in basal half, slightly widened in posterior half, apices rounded, strongly explanate, triangularly emarginate at suture; anterior half of elytra shining, granulate-punctate, with yellowish pubescence, shorter than on pronotum, posterior half matt, glabrous except for a few fine setae on elytral margins and very finely punctulate; a narrow basal area with small granules and dense setae, granules gradually replaced by more widely spaced punctures posteriorly and laterally, punctures small close to suture, coarser laterally, weakly rugulose between punctures; sides of elytra in posterior part with a series of 6‒7 short, parallel, arcuate plicae, convex anteriorly, anterior 2‒3 plicae in posterior part of punctate area of elytra, plicae gradually increasing in length posteriorly to penultimate plica; lateral carinae on posterior part of elytra strong, curved anteriorly at a right angle in posterior quarter of elytra, and running transversely about halfway toward suture; dorsal costae short, weakly raised; suture elevated from about mid-point of elytra, very strongly at top of declivity, where each costa extended into a pointed spine, the spines separated by an angle of about 60 o, and extending over declivity, costae gradually reduced in height on declivity, extending nearly to apex of declivity; each elytron separately concave on declivity, concavity bounded medially by sutural costa, laterally and posteriorly by lateral carina.

Abdomen. Very finely, densely punctured, pubescence rather short with scattered longer erect setae.

Legs. Procoxae strong, globular; profemur stout, ventral face impressed, smooth; protibia short, finely granulate, widened towards apex, external margin with a row of small pointed teeth, terminal spur strong, arcuate tooth at apex strong, but shorter than second tarsal segment.

Female.

Generally resembling male, 14‒15.5 mm in length (mean = 14.75mm, n = 4), about 3.6 times as long as wide, pronotum as wide as long, elytra 2.3 times longer than wide.

Distinguished from male by longer and more erect pubescence on whole of body including legs and ventral side; median clypeal tooth smaller; elytra shining to margin of declivity, dorsum of elytra more coarsely, densely, deeply punctured, punctures sometimes confluent, coarse punctures extending to margins of elytral declivity, sides granulate, lacking plicae, lateral carina short and lacking rectangular bend anteriorly; suture raised in middle of declivity, but much less strongly, and without spine-like processes; declivity more weakly concave, matt, sparsely punctured; legs with pubescence longer, protibia with smaller teeth on lateral margin.

Diagnosis. The male is clearly similar to M. batillus but can be easily distinguished by the form of the sutural costae, each costa extended into a pointed spine, the spines separated by an angle of about 60 o, and extending over declivity; in M. batillus the costae are strongly raised at the upper margin of the declivity, but are evenly arcuate and lack spine-like processes. The dorsal elytral punctures of M. plesiobatillus are more closely spaced than in M. batillus , and the surface is rugulose between the punctures, not smooth and shining. The punctured area extends half the length of the elytra in M. plesiobatillus , but less than half in M. batillus . The series of arcuate plicae on the sides of the elytra in M. batillus is much shorter or absent, and the lateral carina is curved dorsally at a right angle in the apical quarter not at a little more than half the length of the elytra. The female is distinguished with difficulty from the female of M. batillus by the colour of the brush of hairs on the anterior margin of the labrum, and small differences in the elytral declivity.

Distribution. China (Zheijiang).

Etymology. The specific name means near or similar to (Greek: πλησίον) the species batillus .

Remarks. The species was collected in small numbers at the same site as Polycaon sinensis , and numerous specimens of M. batillus , but only at higher altitudes (665‒903 m altitude). It appears to be a montane species, while the more widespread M. batillus is also found at low altitudes.

Figures

FIGURE 2. Males of Melalgus plesiobatillus sp. nov. (a, d, e, g) and M. batillus (Lesne) (b, c, f). a, b. Frontal view. c, e. Lateral view of elytra. d. Dorsal view of head and pronotum. f, g. Dorsal view of elytra.

FIGURE 3. Females of Melalgus plesiobatillus sp. nov. (a–e) and M. batillus (Lesne) (f). a. Dorsal view. b. Lateral view. c. Ventral view. d. Frontal view. e, f. Elytral declivity.