The influences of different aphids as food upon the ecological and morphological characters of the lady beetles Harmonia axyridis Pallas and Coccinella septempunctata bruckii Mulsant (Coleoptera : Coccinellidae) : Laboratory studies on food ecology of aphidophagous coccinellids 1

Larvae of the lady beetles Harmonia axyridis Pallas and Coccinella septempunctata bruckii Mulsant were reared individually with six species of aphids under the experimentally controlled condition of 25℃ and 70-80% R.H., without lighting, and the influences of different aphids as food upon some ecological and morphological characters of these beetles were studied. The results are summarized as follows : 1. The ecological and morphological characters of both species of beetles were varied greatly with the species of aphids given as food. But the degrees of influence were not even with the characters, the sex and the species of beetles. The degrees of influence among the characters were most conspicuous in the preimaginal mortality and were plain in the size of elytron. In comparison of H. axyridis with C. septempunctata bruckii the variation appeared in their characters were more remarkable in the former species. 2. Among prey aphids R. prunifoliae was the most suitable food for H. axyridis, and M. rosae ibarae followed the former. H. arundinis was also an excellent aphid, but inferior to M. rosae ibarae ; B. brassicae was superior to A. magnoliae but somewhat harmful and less suitable than H. arundinis ; A. medicaginis and A. magnoliae were both harmful species for H. axyridis, and the detrimental nature in the former species was especially outstanding. For C. septempunctata bruckii, the suitability of R. prunifoliae and M. rosae ibarae was similar to that for H. axyridis. Further B. brassicae, A. medicaginis and H. arundinis were considerably favorable, but inferior to M. rosae ibarae ; A. magnoliae was strikingly harmful and no suitability was detected. 3. The suitabilities of R. prunifoliae and M. rosae ibarae were perfectly compatible between H. axyridis and C. septempunctata bruckii. In contrast with these species, the harmfulness of A. medicaginis and B. brassicae was highly exclusive with H. axyridis. In spite of marked differen ce in the degree of suitability, H. arundinis and A. magnoliae seemed to be the species that have more or less imperfect compatible suitability for both species of coccinellids. 4. The need of further studies extending over much more species of aphids, coccinellids and other insect species feeding on aphids is stressed in order to make clear the biological meaning of prey specificities of aphidophagous coccinellids and their role in controlling the natural population densities of aphids.