Abstract: The foraging behavior of the lady beetle Propylea japonica to wards the cotton aphid Aphis gossypii was systematically examined. The results indicated that the foraging behavior of the lady beetle changed gradully at different aphicd dersities. When tile aphid density changed from low to high, the lady beetle switchedfrom active search to ambush search, and when the aphid density changed from high to low, the lady beetle switched from ambush to active search. Such behavioral change resulted from the integrated effect of the amount of food alreadly present in the gut and the encounter rate with aphids. We suggest that better control effect of the lady beetles on cotton aphids might be gaind by regulating their density ratio.

Key words: Propylea japonica, Aphis gossypii, foraging behavior