Aphid consumption and residence time of larvae of flightless lady beetles, Harmonia axyridis (Coleoptera: Coccinellidae), on aphid-infested plants

A flightless strain of the lady beetle, Harmonia axyridis Pallas, has been established, by artificial selection, for effective biological control of aphids. However, this biological control technique is costly because of the high cost of production of the adults. It is, therefore, important to consider the utility of the larvae in biological control. This study examined the potential for larvae of the flightless strain to be used as biological control agents compared with those of the wild-type, in terms of how they behave on aphid-infested plants. We found no differences between the strains with regard to residence time and aphid consumption on the plant for the first, second, and fourth instars, and at low and high aphid densities. In contrast, however, aphid consumption by third-instar larvae of the flightless strain tended to be lower, although they remained on the plant longer than third-instar larvae of the wild-type. Consequently, our results suggest the flightless strain does not differ from the wild-type in its ability to control aphids across all larval stages, except for the third instars. On the basis of these results, and in conjunction with the results from previous studies, we discuss the appropriateness of different larval instars for release.