The labybird Harmonia axyridis is well known as an aggressive intraguild predator in communities of aphidophagous insects in Japan. To understand and compare the effects of H. axyridis, and a second abundant ladybird, Coccinella septempunctata, on larval performance of co-occurring aphidophagous insects, factorial experiments involving the removal of one of or both predators were carried out on hibiscus trees in the field. The aphidophagous guild consisted of five ladybird species and three hoverfly species. The mortality rate of C. septempunctata significantly increased when H. axyridis was present. There were also significant differences in the larval mortality of the ladybird, Propylea japonica and in the number of hoverflies present among the treatments. Negative effects of H. axyridis on other species were stronger than those of C. septempunctata. The number of individuals of the ladybird, Scymnus sp. did not differ between the treatments. This species emerged earlier than H. axyridis did, and left trees to pupate else where before the occurrence of 3rd and 4th instar larvae of H. axyridis and C. septempunctata on the trees. Our results suggest that IGP by H. axyridis strongly influenced aphidophagous guild structure, and that the strength of interactions among the predators varied both with development of the key species and with aphid abundance.