Identification of Harmonia axyridis and H. yedoensis with notes on the former′s color pattern and elytral ridge occurrence

Key Words：Coccinellidae, Harmonia axyridis, Harmonia yedoensis, morphology, sibling species

Abstract：      The two ladybird beetles, Harmonia axyridis (Pallas) and H. yedoensis (Takizawa) (Coleoptera: Coccinellidae) are sibling, often sympatric, species found in China (from Beijing in the north to northern part of Guangdong in the south, to eastern Xizang and southern Gansu in the west), Japan (south of Hokkaido) and Korea. These insects occur simultaneously on some plants, most frequently on pine trees. H. yedoensis had long been regarded as a synonym of H. axyridis, including recently by Koch (2003). Because adults of these two forms are difficult to distinguish in the field, there is potential to make wrong explanation for the variation of elytral color pattern, ridge occurrence and the microevolution in H. axyridis. This paper describes the color pattern and elytral ridge of H. axyridis in parts of North China lacking H. yedoensis. The axyridis form is very rare in the eastern part of China (from North China to north Guangdong in the south, to Gansu and Yunnan in the west) but is common in northwest Xinjiang. The frequency of elytral ridges ranges from 98.85% in North China (Jiamushi City, Helongjiang Province) to 78.26% in West China (Dali City, Yunnan Province). The paper lists diagnostic characters for identifying these two species and details their natural distribution. Although the presence of an elytral ridge identifies specimens as H. axyridis, it is hard to determine from external characters if specimens lacking an elytral ridge and in forms of axyridis, spectabilis or conspicua. Fortunately, the mature larvae can easily be distinguished from each other. Illustrations of male genitalia and color photographs (including those of larvae) are provided.