Rapid population growth and food-plant exploitation pattern in an exotic leaf beetle, Ophraella communa LeSage (Coleoptera : Chrysomelidae), in western Japan

An exotic leaf beetle, Ophraella communa, originating from the Nearctic reg ion, is a multivoltine oligophagous herbivore and was discovered in Japan i n 1996. The host-use of the leaf beetle in the field with adult feeding cho ice and larval performance on some asteraceous plants in the laboratory wer e surveyed. O. communa showed a hierarchy of food-plant use: The leaf beetl e first used Ambrosia artemisiifolia, on which adults preferred to feed and larvae developed well, and its population increased markedly until defolia ting this food-plant. Then, the leaf beetle migrated to Am. trifida and Xan thium spp. In the laboratory, Am. trifida was not as preferred by adults as Am. artemisiifolia, although larval performance on Am. trifida was superio r. Xanthium was inadequate both in terms of adult feeding choice and larval performance. Neither eggs nor larvae were found on the plant species on wh ich no larvae completed their growth in the laboratory. These findings sugg est that the exotic beetle has great mobility and host-discriminating abili ty. The finding, that Am. trifida was less used than Am. artemisiifolia des pite Am. trifida being suitable for larvae, may be attributable to the fact that adults tend to oviposit on Am. trifida subsequently to feeding.