Lignyodes japonicus Kojima and Morimoto

Kojima, Hiroaki & Morimoto, Katsura, 2003, A New Lignyodes Dejean, A New Representative of the Genus and the Tribe Lignyodini from the Eastern Palaearctic Region (Coleoptera: Curculionidae), The Coleopterists Bulletin 57 (4), pp. 383-389 : 384-389

Lignyodes japonicus Kojima and Morimoto , new species

Figs. 1–15

Diagnosis. Pronotum and elytra with yellowish grey scales, lacking pattern of variously colored scales ( Fig. 1 ); rostrum ( Figs. 2–3 ) long, slender, arcuate; integument rufous except faintly dark head and rostrum; aedeagus asymmetrical at apex ( Fig. 10 ).

Description. Male. Length: 2.65 mm. Width: 1.35 mm. Head: scales on vertex seta-like, replaced posteriorly and ventrally by slender, acuminate scales; scales on gena broad, whitish; eyes moderately large, slightly prominent, separated by distance 0.2 3 eye length, eye width 1.3 3 length. Rostrum ( Fig. 2 ) slender, 1.2 3 pronotal length; in profile, evenly arcuate from base to apex; in dorsal view side slightly tapered to subparallel from base to level of antennal insertion, slightly narrowed distad of insertion, then slightly expanded to apex, there wider than rostrum at base; proximal portion 60% of total rostral length, with shallow lateral and dorsolateral sulci, glabrous, except for dorsolateral setae and narrow scales at extreme base; distal half shallowly sulcate, glabrous, except for few small setae; dorsal margin of scrobe carinate to eye; antennal club ( Fig. 8 ) with 3rd and 4th articles subequal in length, their combined length of nearly as long as 2nd. Prothorax ( Fig. 1 ): 1.4 3 as wide as long, nearly as wide as elytra at base; sides strongly rounded from base to feebly developed subapical constriction; disc with short, narrow, apically attenuate, recumbent scales, with admixture of slightly larger, feebly raised scales; pleura with broader scales. Elytra ( Fig. 1 ): in dorsal view, humeri not prominent, sides subparallel to middle; interspaces flat, odd-numbered slightly wider than, but not more convex than even-numbered; surface of each interspace slightly irregularly, shallowly, discretely punctate; slightly raised scales uniseriate on each interspace. Abdomen: sterna 1 and 2 slightly, continuously, concave medially; sterna 3–4 flat; sternum 5 shallowly but distinctly concave medially; sides of sterna 1–4 with whitish, oblong scales; sides of sternum 5 with acuminate seta-like scales, median portion of sterna 1 and 2 with sparse, recumbent setae; sterna 3–5 with denser, recumbent setae. Legs ( Figs. 4–5 ): femora uniformly clothed with long, finely acuminate, recumbent seta-like scales; protibia with large uncus, praeomucro obsolete, metabitial uncus small, with slight basal prominence. Genitalia ( Figs. 10–11 ).

Female. Length: 2.60–2.90 mm. Width: 1.30–1.40 mm. Rostrum ( Fig. 3 ): 1.20–1.25 3 pronotal length; proximal portion 48–50% of total rostral length; entire rostrum with obsolete punctation. Legs ( Figs. 6–7 ): protibia with curved uncus; metatibia with shorter, perpendicular uncus. Spiculum ventrale: ( Fig. 13 ). Spermatheca: ( Fig. 12 ).

Type Material. Holotype female (Type No. 3144, ELKU): JAPAN: Honshu. Mt. Soumon , Miyagawa , Mie Pref., 1.viii.1998, K. Kanno . Paratypes. JAPAN: Honshu . Takenari , Komono , Mie-Pref. , 9.viii.1997, K. Kanno (1 female, ELKU); Wakaura , Wakayama City, 16.viii.1990, M. Kitahata (1 female, IM); 16.ix.1991, M. Kitahata (1 male, ELKU) .

Distribution. Japan (Honshu-Kii Peninsula).

Discussion

Relationships. This species is superficially similar to L. helvolus (LeConte) and L. auratus Clark from North America and L. uniformis Desbrochers and L. dieckmanni Clark and Lodos from Europe in lacking a scale pattern on the elytra. Lignyodes japonicus differs from L. helvolus and L. auratus in the structure of the antennal club. Both have the 2nd segment longer than the 3rd and 4th segments combined and the symmetrical apex of aedeagus as in North American species. Lignyodes japonicus also differs from L. uniformis and L. dieckmanni in its smaller body (2.6–2.9 mm in L. japonicus , but more than 3.5 mm in L.uniformis and L. dieckmanni and the shape of apices of the aedeagus and rostrum are different (see Figs. 1 , 6 and 7 of Clark and Lodos 1981).

The asymmetrical apex of the aedeagus occurs in European species and some North American species such as L. horridulus (Casey) , L. bischoffi (Blatchley) and L. arizonicus (Sleeper) . The shape of the apex of the aedeagus of L. japonicus is similar to those of L. horridulus and L. uniformis . However, the orificial sclerite and spiculate structures of the inner sac are different from those of L. japonicus . These structures are similar to L. fraxini (LeConte) although the latter has an aedeagus with a symmetrical apex. The antennal club and rostrum of L. japonicus are similar to those of L. bischoffi and L. fraxini , but the latter two species have differently formed tibiae and/or unci. The tibial structure of L. japonicus is similar to L. horridulus or L. arizonicus . Thus, it is difficult to determine the closest relative of L. japonicus at present without phylogenetic analysis. But, judging from characters observed, L. japonicus may have some affinity with the North American species L. bischoffi , L. arizonicus , L. fraxini or L. horridulus .

Biology. Biological information is rather restricted for L. japonicus ; one adult was collected on leaves of Quercus phillyraeoides by beating and one other came to a light trap. The habit of flight to light was already known for this group, and judging from the previous host records of this genus, the collection from Quercus phillyraeoides is probably incidental. Thus, the Japanese species, is most likely associated with the genus Fraxinus as is the case with other species. Although this species is rare in collections, an intensive survey of Fraxinus and use of light traps for collecting around the known localities probably will be successful to increase samples available.

Distribution and Biogeography. Discovery of this weevil from Japan not only extends the distribution of the genus, but also that of the tribe/subtribe in the fauna of the eastern Palaearctic region. This fact suggests the possibility that the same group at the species level as well as at higher taxonomic levels may occur in other parts of the East Asia.

The present discovery also represents a disjunct northern distribution pattern that can be explained on the basis of Bering Arc relationships ( Fig. 14 ). Linsley (1963) studied distributions of Cerambycidae and divided them into two groups: one with Vancouveran-Japano-Manchurian and Vancouveran-European relationships and the other with Alleghenian-Japano-Manchurian and Alleghenian-European relationships, depending on whether East Asian and European groups have affinity with western or eastern North America. Lignyodes (Lignyodes) is more abundant in eastern rather than western North America (six of the eight species occur in eastern North America), and European species seem to have affinities with eastern North American species (Clark and Lodos 1981). Thus, judging from the distribution, this group will show the Alleghenian-Japan and Alleghenian-Europe relationships.

This species has been collected only from the central part of Japan: Kii Peninsula ( Fig. 15 ). If the ash tree is regarded as the host of this weevil, it is possible it will be collected from other areas. Another weevil, Ochyromera suturalia Kojima and Morimoto , is associated with Fraxinus and the larval habitat in seeds is exactly the same as Lignyodes species (Kojima and Morimoto 1996). In Japan, O. suturalis is known to occur in the north on the Japanese Sea side opposite the Pacific, where L. japonicus occurs. Because several species of Fraxinus are known from Japan, the two weevils may coexist with each other if they feed on different species of Fraxinus . Presently, it is uncertain why L. japonicus has been found only in the limited area. However, intensive surveys of East Asia will probably find other species of Lignyodes on Fraxinus .

Figures

Fig. 1. Habitus of Lignyodes japonicus new species.

Figs. 2–13. Characters of Lignyodes japonicus. 2) Head, lateral view, male; 3) head, lateral view, female; 4) fore tibia, male; 5) hind tibia, male; 6) fore tibia, female; 7) hind tibia, female; 8) antenna, male; 9) antenna, female; 10) aedeagus; 11) 8th and 9th sternites, male; 12) spermatheca; 13) 8th sternite, female.

Fig. 14. Distribution of the subgenus Lignyodes.

Fig. 15. Distribution of Lignyodes japonicus.