Abstract: An investigation was conducted to study the ant associated with nigra scale (Parasaissetia nigra) in Yunnan rubber planting area. A total of 22 ant species were collected, belonging to 15 genera and 4 subfamilies, and Oecophylla smaragdina was the dominant species. Field survey found that the rubber trees with ants presented had higher probability damaged by the scale. To understand the interactions between the scale and ant, two rubber trees with ants and scales in a rubber plantation were selected, and the survey showed that there was a positive correlation between the amounts of the scales and ants. The more the ants presented, the more serious damage caused by the scales. The distance from the ant nests also affected the quantity of the scales,i.e., the nearer the nest, the more the scale individuals presented. After ant isolation, the 2nd generation mortality of the scales and the parasitism rate of chalcids decreased, and accordingly, the scale population increased. These results demonstrated that the existence of ant protected the nigra scale, and their relationship was mutualism.

Key words: Acacia auriculiformis, Azadirachta indica, nutrient cycling, dry-hot valley.