Abstract
Intensive and successive field surveys on the relative abundance of Nezara viridula (Hemiptera: Pentatomidae) and N. antennata at various localities in northern Kyushu, Japan, together with scattered collection records of N. viridula in Kyushu and Honshu, clearly showed that N. viridula has been expanding its range northward since the 1960s. The present range of N. viridula in Kyushu coincided well with the areas where the mean temperature of the coldest month exceeds 5°C that has been suggested to be the lowest thermal limit for N. viridula to overwinter successfully. The future range of N. viridula is predicted to cover a large area of Kyushu if the temperature rises by 1.4 to 5.8°C by 2100. In some places, N. antennata seemed to have been replaced by N. viridula as a result of their interspecific mating that prevented N. antennata from intraspecific mating. This is because N. antennata was overwhelmed, in abundance, by N. viridula, which has a higher reproductive potential than N. antennata under warm conditions with a sufficient amount of food resources. Conversely, N. antennata populations recovered in a few places where N. viridula had replaced N. antennata in the 1950s, probably due to the shortage of rice plants on which N. viridula preferably reproduces.
