Life history characteristics and changes in distribution of the alien grasshopper Atractomorpha sinensis in Osaka Prefecture, Japan

Abstract

To evaluate the impacts of the alien grasshopper Atractomorpha sinensis on agricultural crops in Japan, field surveys and laboratory experiments were conducted, and the results were compared with those obtained from the native grasshopper A. lata. The seasonal occurrences of A. sinensis and A. lata were recorded in 2022 and 2024 in Osaka Prefecture. The adult population density of A. sinensis exhibited two peaks, one in early summer and another in autumn, while A. lata showed only a single autumn peak. In addition, the abundance of both species was compared at seven sites, each at different altitudes, in southern Osaka Prefecture in 2017, 2022 and 2024. The distribution of A. sinensis was observed to expand annually from lower to higher altitude sites, and once it invaded a site, that site became dominated by A. sinensis within a few years. The flight ability of A. sinensis was markedly higher than reported previously, which is likely a key factor underlying the rapid spread of this species in Japan. Mating experiments revealed frequent interspecific mating. Given that the adult seasons of both species overlapped in autumn, such interactions likely occur in the field and may negatively affect A. lata. The findings suggest that range expansion in A. sinensis has resulted in the displacement of A. lata, and that agricultural crops may be damaged at unexpected times because of the ability of A. sinensis to produce two generations a year.