Xylothrips Lesne, 1901

Liu, Lan-Yu, 2021, A review of the powderpost beetle genera Xylothrips Lesne, 1901 and Calophagus Lesne, 1902 (Coleoptera: Bostrichidae: Bostrichinae: Xyloperthini), European Journal of Taxonomy 746 (1), pp. 130-147 : 132-134

Genus Xylothrips Lesne, 1901

Figs 1C–F , 2–3

Xylothrips Lesne, 1901: 620

(type species: Apate flavipes Illiger, 1801: 171 by subsequent designation in Chûjō 1937: 58).

Diagnosis

As a member of Xyloperthini , the genus is characterised by the lamelliform intercoxal process of the first abdominal ventrite, the mandibles crossed at the tips and the well-developed to elongated antennal club ( Lesne 1921; Fisher 1950; Liu & Schönitzer 2011). The genus is distinguished from all other genera of Xyloperthini by the following combination of characters: antenna with ten antennomeres, the funicle with five, and club with three antennomeres, the funicle as long as the first club segment with a rim of long, erect hairs around each segment, antennal club matt without clear sensory impressions or stiff hairs, with a series of erect hairs on the inner side and one long erect hair on the anterolateral angle of each club segment ( Fig. 1C, E ); long and distinct lateral ridge-like carinae on pronotum ( Fig. 1D, F ), which form the acute posterolateral angles of the pronotum; elytral suture slightly raised behind the summit of declivity, but not swollen at all ( Figs 2D , 3B ); both sexes with pleural pieces at sides of last ventrite ( Fig. 2E ). The species are 5.5‒8.5 mm long.

Compared with Xylothrips , the other four genera of Xyloperthini with ten antennomeres which occur in the same geographical area, i.e., Calonistes Lesne, 1936 , Xylocis Lesne, 1901 , Xylophorus Lesne, 1906 and Paraxylion Lesne, 1941 , can be distinguished by the lack of lateral carinae on the pronotum and being less than 5.5 mm in length. Paraxylion can also be distinguished by the two circular sensory areas close to the anterior margin on the first and second club antennomeres. In the tribe Xyloperthini , only Amintinus Anonymous, 1939 ( Ivie 2010) , Xylopsocus Lesne, 1901 and Xylothrips possess the ridgelike ‘true’ lateral carina of the pronotum ( Lesne 1932, 1938b). Amintinus is an African genus with species about 3.0‒ 3.5 mm in length without marginal tubercles on the elytral declivity, the lateral margin prominent and the lower apical margin thickened, emarginated. Xylopsocus can be distinguished by the lack of pleural pieces at the sides of the last ventrite of the male, smaller size (about 3.5‒4.5 mm in length) and the presence of only 9 antennomeres in a few species ( X. capucinus (Fabricius, 1781) , X. intermedius Damoiseau in Damoiseau & Coulon, 1993 and X. radula Lesne, 1901 ).

Description

BODY. Elongate, cylindrical, 5.5–8.5 mm long.

HEAD. Deeply inserted in prothorax, not visible from above. Frons simple, finely punctured, with upwardly directed hairs, denser and much longer in female, fronto-clypeal suture distinct, strongly impressed in middle; clypeus transverse, anterior margin forms an arc in the middle, finely and densely punctured; labrum transverse with a fringe of long hairs along anterior margin. Mandibles subequal, sharply pointed. Eyes rather large, oval, detached from temples posteriorly. Antenna with 10 antennomeres, first two elongate, antennomeres 3–7 forming a funicle, each antennomere transverse, the fifth widest, together about as long as first antennomere of club, antennomeres 8–10 forming elongate club, about twice as long as rest of antenna; lacking distinct, clearly defined sensory impressions or stiff hair area on all antennomeres; first two antennomeres of antennal club about 1.2 –1.5 times as long as wide and last antennomere slender, about 2–3 times as long as wide, elongate oval.

PRONOTUM. Slightly wider than long, anterior angles with a rather long, upcurved uncinate tooth; sides moderately to broadly rounded, attenuated anteriorly, widest close to posterior margin of pronotum; anterior margin between unci concave, rugose; area above anterior margin flat or weakly impressed, and strongly, densely punctured; with a series of upwardly-directed teeth laterally, gradually reduced in size from anterior to posterior, mixed with small teeth and tubercles to summit of pronotum, with fine, shallow, well-separated punctures; sides with distinct ridge-like lateral carinae which extend along posterior margin and form sharply tipped posterolateral angles; ventro-lateral punctures with sparse, long, white pubescence.

SCUTELLUM. Small, tongue-shaped, finely punctured or glabrous, shining.

ELYTRA. Subequal to pronotum in width, strongly convex, shining, and strongly, evenly punctured, almost glabrous on disc and declivity, only sparse and very tiny pubescence on apical part of declivity, sutural margin slightly raised from summit to near apex of declivity and rather strongly raised at apex of declivity. Upper margin of declivity with three pairs of tubercles and one pair of elongate calluses at side.

ABDOMEN. Ventral side covered by short, white pubescence, last ventrite with narrow pleural pieces along margin and a tuft of long hairs in middle in both sexes.

LEGS. Subequal in length, procoxae contiguous, mesocoxae narrowly separated, pro- and mesotibiae grooved on external face, widened to apex. Posterior tibiae with a few long bristles on outer side, very dense, short, golden hairs rimming ventroposterior margins of posterior femora. Second and third segments of tarsi usually distinctly wider than following segments.

Sexual dimorphism

The genus shows clear sexual dimorphism in the vestiture of the frons. In the female, the frons is more densely and finely punctured, and the upwardly directed hairs are much longer and denser than in the male. The frontal hairs are yellowish, forming a crown with rather short, erect hairs inside. In the male, the frontal hairs are short with only a small tuft of very long hairs next to the eyes.

Biology

As a member of the dry wood borer family Bostrichidae , Xylothrips usually occurs in forest habitats (pers. obs.). From the records of host plants, the genus, like almost all other bostrichids, is certainly polyphagous and attacks orchard trees as well as forest trees ( Lesne 1901, 1932; Stebbing 1914; Beeson & Bhatia 1937). In tropical areas, there is more than one generation per year ( Beeson & Bhatia 1937), and high populations can cause economic problems in orchards and other forest plantations.

Distribution

India, Nepal, Southeast Asia, Australia, the archipelagos of the Indian Ocean and Pacific Ocean, Madagascar.

Figures

Fig 3. Xylothrips religiosus (Boisduval, 1835), ♀ (LYL). A. Frontal view. B. Dorsal view. C. Declivity. D. Lateral view of declivity. E. Lateral view. Scale bars = 1 mm (upper scale for B, E; lower scale for A, C–D).

Fig. 1. A–B. Calophagus pekinensis Lesne, 1902, ♀ (SNSD). A. Anterolateral view showing the antennae, with two strips of golden hairs on sides. B. Lateral view of head and pronotum showing absence of lateral carina on pronotum. C–D. Xylothrips flavipes (Illiger, 1801), ♂ (LYL). C. Frontal view showing the antennae, matt without sensory areas. D. Lateral view of head and pronotum showing clear lateral carina on pronotum. E–F. Xylothrips religiosus (Boisduval, 1835), ♂ (LYL). E. Frontal view showing the antennae, matt without sensory areas. F. Lateral view of head and pronotum showing clear lateral carina on pronotum. Scale bar = 1 mm.

Fig. 2. Xylothrips flavipes (Illiger, 1801), ♀ (LYL). A. Frontal view. B. Lateral view of declivity. C. Declivity. D. Dorsal view. E. Ventral view. Scale bars = 1 mm (upper scale for A–C; lower scale for D–E).