Sikkimia Duvivier, 1891

Lee, Chi-Feng & Bezdek, Jan, 2016, Revision of the wingless Sikkimia Duvivier (Coleoptera, Chrysomelidae, Galerucinae) from Taiwan, including a new generic synonymy and four new species descriptions, ZooKeys 553, pp. 79-106 : 80-83

Taxon classification Animalia Coleoptera Chrysomelidae

Genus Sikkimia Duvivier, 1891

Sikkimia Duvivier, 1891: 154 (type species: Sikkimia antennana Duvivier, 1891, by monotypy); Maulik 1936: 520 (redescription).

Yunomela Chen, 1964: 201 (type species: Yunomela rufa Chen, 1964, by original designation); Bezděk and Zhang 2006 (as synonym of Sikkimia ).

Taiwanolepta Kimoto, 1989: 73 (type species: Taiwanolepta babai Kimoto, 1989, by original designation). New Synonym

Vietocerus Lopatin, 2003: 103 (type species: Vietocerus kabakovi Lopatin, 2003, by original designation); Bezděk and Zhang 2006 (as synonym of Sikkimia ).

Remarks.

The diagnostic characters for the genus Sikkimia , as indicated by Bezděk and Zhang (2006), are modified and extended as follows: body large (6.1-12.0 mm), robust, orange, red or brown; last two segments of antennae strongly enlarged in most males (Figs 1-2); frontal tubercles large, sub-quadratic; pronotum with antebasal transverse impression, limited on sides by short longitudinal furrows, and an additional longitudinal groove half way between short longitudinal furrows and lateral margin, running parallel to the lateral margin (Fig. 1); all pronotal margins bordered; procoxal cavities closed; apical ventrite trilobed in male, with internal anterior margin extended (Figs 7, 48 & 49); and claws appendiculate.

As all the main diagnostic characters are shared by both the continental and Taiwanese species, Taiwanolepta is here synonymized with Sikkimia . Taiwanese species differ from the continental species in having a shorter body (6.1-9.0 mm) reduced hind wings and consequently reduced humeral calli. The apical antennomere in the male is spear-shaped and more or less symmetrical in continental species (Fig. 2, see also the drawings in Bezděk and Zhang (2006)), while strongly asymmetrical in Taiwanese species (Figs 24-47). Outer longitudinal grooves on pronotum are deeper in Taiwanese species while more feeble in continental species. Aedeagus sclerotized ventrally in Taiwanese species, but membranous in continental species. Internal sclerite divergent apically in almost all Taiwanese species (Figs 19, 53, 66, 86), while the continental Sikkimia rufa has the sclerite divergent basally (Fig. 3). On the other hand, the structure of the spermatheca, gonocoxae, ventrite VIII and extended internal part of male abdominal ventrite V in the male are very similar (these structures of Sikkimia rufa as in Figs 5-8, and for the other Taiwanese species as in Figs 21-23, 48, 49, 55-57, 68-70, 81-83).

Biology.

Taiwanese species of Sikkimia appear to be univoltine, based on field observations. Larvae are nocturnal and found on the underside of the host plant’s leaves between February and April. Larval development takes about 20-22 days, based on laboratory rearing. Mature larvae leave the host plant and burrow into the soil where they build underground chambers for pupation. The pupal stage lasts for 22 days, and adults begin to emerge after April. The adults are also nocturnal and live for more than three months, a lengthy longevity for chrysomelids. Females deposited single eggs on leaves under laboratory conditions, but these failed to hatch. Presumably Sikkimia species overwinter as adults, as some females were collected during winter.

All known Sikkimia species feed on the leaves of Polygonum chinense L. ( Polygonaceae ) (Fig. 9). However, some populations of Sikkimia tsoui sp. n. also feed on other plants in different areas. For example, populations from Yangminshan National Park (including Hsiaoyuken, Erhtzuping, Lengshuiken, Tatunshan) have been observed feeding on Rubus swinhoei (Fig. 15) and Rubus corchorifolius (Fig. 10) ( Rosaceae ), and members of populations from Tahunshan feed on Dumasia miaoliensis subsp. bicolor (Fig. 11) ( Fabaceae ). Specimens from these populations will feed on Polygonum chinense if switched from their original host plant.

In Taiwan, leaf beetles from three genera are known to feed on Polygonum chinense . These include Altica birmanensis (Jacoby, 1896) ( Lee and Cheng 2007), Gallerucida singularis Harold, 1880 ( Lee and Bezděk 2013), and Sikkimia species. Altica birmanensis inhabits lowlands, at elevations below 1200 m. Gallerucida singularis occurs at slightly higher elevations, ranging between 1000 m and 1500 m. Sikkimia species occupy the higher elevations, and are found from 1000 m to 2500 m in central and southern Taiwan. Thus Gallerucida singularis is sympatric with Sikkimia species in some areas. Although members of both taxa are nocturnal, their larvae prefer different sites on the host plant. Larvae of Gallerucida singularis always appear on the upper surface of leaves, their body segments lack lateral expansions, and the apical posterior tergites are narrower (Fig. 12). Sikkimia larvae occur on the underside of leaves, each body segment has lateral expansions, and the apical posterior tergites are wider (Figs 9-11).

Distribution.

China, India (Sikkim), Laos, Myanmar, Taiwan, and Vietnam.