Genetics of the two colour forms of Chrysolina aurichalcea (Mannerheim) (Coleoptera: Chrysomelidae) and their gene frequencies in two mountainous areas of central Honshu, Japan

Abstract

Chrysolina aurichalcea (Mannerheim), which is common all over Japan, is univoltine and feeds mainly on Artemisia princeps. It is well known that this species has two forms according to the dorsal colour of the adults, i.e. a cyaneus-form and a cupreous-form. Many studies have been made of the frequency distribution of the two colour forms (e.g. Ohno 1964, Kimura 1965, Suzuki et al. 1975a, Baba and Kato 1978, Fujiyama 1979). However, mass-sampling at each habitat has only been undertaken since Suzuki et al. (1975b). Three main points emerged from these works. Firstly, the geographic variation in the frequency of the two colour forms has no obvious tendency comparable with that of the spotted pattern in Harmonia axyridis (Komai, 1956). This complex variation was discussed in relation to the restriction of adult migration by reduced wings, though flying populations were recently found by Suzuki (1978). Secondly, major populations have a high frequency of the cyaneus-form, but some populations from the Pacific coast (Suzuki et al. 1976. Suzuki and Sakurai 1977, 1978, Suzuki and Ozaki 1980) and from mountainous areas (Fujiyama 1979) have a high frequency of the cupreous-form. Thirdly, although neighbouring populations usually show similar frequencies, drastic changes in the frequencies are seen in some cases (e.g. see Suzuki et al. 1976, Baba and Kato 1978, Fujiyama 1979). Subsequently, Suzuki and Ozaki (1980) proposed a subdivision of the cyaneus-form and cupreous-form into three and eight colour forms, respectively.