Abstract. Aphids of the tribe Pemphigini (Hemiptera: Aphididae: Eriosomatinae) can induce pseudo-galls or galls on their primary host plants. Those belonging to subtribe Prociphilina often produce pseudo-galls, and those of the other subtribe, Pemphigina, can form not only pseudo-galls but also true galls. Pseudo-galls are all formed on the leaves, whereas true galls, although all similar in shape, can be located on the joint of the leaf blade and the petiole, the middle of the petiole and the branches of the host plant. From a first phylogenetic analysis of Pemphigini based on nuclear elongation factor-1a (EF-1a) sequences, no support was found for the monophyly of Pemphigini, but subtribe Pemphigina was monophyletic with robust support. Formosaphis obviously clusters with Pemphigina which has Populus as a primary host. Formosaphis belongs to Pemphigini and its unknown primary host is probably Populus. The evolution of galls in Pemphigina is discussed based on the phylogenetic tree drawn from EF-1a sequences and mitochondrial cytochrome oxidase subunit I (COI) sequences. The results suggest that, in this subtribe, the closed gall is preceded by an open pseudo-gall, and the galls move their locations from the joint of the leaf blade and the petiole to the middle of the petiole and, eventually, to the branch of the host plant. Such an evolutionary tendency may provide aphids with more protection and nutrition.

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