In the lifecycle of pinebast scale Matsucoccus matsumurae, the populations of its natural preyers varies as follows: when the pinebast scale appears as nymphs (female imago and egg sac), the numbers of preyers on the tree branches are larger than those on the tree trunks, but things are quite different when it appears as a nymph in the first stage. When there is a simultaneous occurrence of the scale and the pine aphid, the population of the preyers increases considerably, mostly due to the increased number of the two pests, and are more inclined to prey on the pine aphids. Ladybugs Sticholotis punctus Crotch, Exochomus monol Baovsky and Sospita chinensis Molsant prey on the scales, while the ladybugs Ballia obscurosignata Liu prey mainly on the phids.