Effects of Two Prey Species Combinations on Larval Development of the Predatory Ladybird Cheilomenes propinqua

Feeding on mixed, alternating or changing diets often favor insect development. With the aim to optimize mass rearing and use for biological control of insect pests we investigated effects of various combinations of high-quality (the green peach aphid Myzus persicae) and low-quality (eggs of the grain moth Sitotroga cerealella) foods on larval development of a predatory ladybird Cheilomenes propinqua. In the first experiment, eggs and aphids were mixed in different proportions; in the second experiment, larvae switched from feeding on aphids to feeding on eggs. Benefits of combined diets to larval development were found in none of the experiments. Feeding on various combinations of eggs with aphids never resulted in higher survival, faster development, or larger size of emerging adults than those observed for feeding only on aphids. For the practice of biological control, we conclude that, if necessary (for example, in case of temporary shortage or lack of aphids in mass rearing facilities or in case of preventing release of C. propinqua adults in greenhouses), C. propinqua larvae can be fed with the grain moth eggs by replacing, mixing, or alternation with aphids but this will inevitably result in a proportional decrease in pre-adult survival, rate of development, weight and size of emerging adults