Ctenocallis setosa (Kaltenbach, 1846) (Hemiptera, Aphididae), a new adventive species in Japan

Numerous species of adventive aphids in Japan exhibit a strong association with naturalized plants, making the aphid studies on such plants crucial for the early detection of newly introduced species. During 2017–2018 and 2023–2024, we examined the aphids occurring on a naturalized plant, Cytisus scoparius (L.) Link (Fabaceae) in Japan, documenting the occurrence of a new adventive species, Ctenocallis setosa (Kaltenbach, 1846) in the country. This represents the first record of this species also from Asia, as it is native to Europe and had previously been adventive only in North America. This paper provides the photographs and morphological redescriptions of its viviparae (apterous and alate) and sexuals (oviparae and alate males). The findings from this field study suggest that this species exhibits a monoecious holocyclic life cycle in Japan, characterized by the sexual morph production for laying overwintering eggs in fall and the absence of host alternation during summer.