Abstract:  Morphological adaptation of insects to their host plants is an important part of the relationship between the two types of organisms. This paper dealt with herbivorous aphids to study their morphological adaptation on different host plant leaves. Twenty-six aphid species which feed on the leaves of 7 genera host plants belonging to 4 families (Poaceae, Salicaceae, Fagaceae, and Pinaceae) were studied. Based on alate viviparous females and apterous viviparous females, 37 morphological characters were compared and measured by using light microscope. Then the characters were statistically analysed. Based on the clone means, with the variables such as ultimate rostral segments, tarsi and claws which are related to aphid feeding behavior and adhesion on the surfaces of plants, three clustering dendrogram (alate viviparous female, apterous viviparous female, all morph) were output and mapped with host plant families and genera. The results indicated that some characters of the aphids, such as body, siphunculi and antennae, were different among different aphid families, but some of them, such as the ultimate rostral segments, tarsal segments Ⅰ, tarsal segments Ⅱ and claws, varied among different host plant families. The variations of morphologies within species were within a range with their CV (coefficient of variation) between 1.89% and 26.08%. The clustering analysis showed that the aphids were divided into the clusters which were corresponding to certain host plant family/genera; and the positions of Doraphis populi, Epipemphigus imaicus and Pemphigus matsumurai were special, because the first is the secondary host-plant morph and the latter two are the gall makers. The results suggest that the distinct separation of the aphid species with respectively different morphological character variations is corresponding to different host plants whose surface structures are diverse. These prove morphological adaptation of aphids to host plants.

Key words: Aphid, morphological adaptation, host plant leaf, Poaceae, Salicaceae, Fagaceae, Pinaceae