Alterations in foraging behavior of Coccinella septempunctata and Propylea japonica mediated by a novel defended prey affect their predatory potential

Generalist aphidophagous coccinellids have to cope with novel prey aphids in environments that are changing rapidly because of anthropogenic activity. The goldenrod aphid, Uroleucon nigrotuberculatum (Olive) (Hemiptera: Aphididae), is a noxious prey, which was recently introduced into Japan. It is a major prey for the native Japanese predators Coccinella septempunctata bruckii Mulsant and Propylea japonica (Thunberg) (both Coleoptera: Coccinellidae) in early summer on patches of solidago, Solidago altissima L. (Asteraceae). Prey preference of these coccinellids between this aphid and a native suitable prey aphid, Megoura crassicauda Mordvilko (Hemiptera: Aphididae), as well as their foraging behavior were studied for a better understanding of the negative impacts of the noxious novel aphid. Coccinella septempunctata initially preferred the novel prey, but later switched to the native prey, M. crassicauda; P. japonica had no preference for either prey. Feeding time of the first instars of C. septempunctata on U. nigrotuberculatum was significantly longer than that of P. japonica. The foraging bouts of fourth instars of C. septempunctata were significantly longer on U. nigrotuberculatum than on M. crassicauda, whereas only the feeding time of fourth instars of P. japonica on U. nigrotuberculatum was significantly longer than on M. crassicauda. Both coccinellids consumed less of U. nigrotuberculatum than of M. crassicauda. Thus, solidago patches infested by U. nigrotuberculatum may present an ecological trap, especially for C. septempunctata.