Abstract:

The effect of urban air pollution on the populations of the scale insects, Eulecanium gigantea (Shinji) and E.kuwanai kanda in the planted street affo restation trees was studied in Taiy uan City from 1994 ~ 1995.The accumulative amounts of city air pollutants SO₂ and Pb in the bodies of the soft scales and their host plant Sophora japonica were determined by the methods of analy tical chemistry.The results showed as follows :1.The scale insect population density (SIP) is positively correlated with the number of cars (Aut.No) driving in a certain district.The correlation equation is Y (SIP) =-30.508 +0.0441X (Aut.No) and the co rrelation coefficient is r =0.895.The scale population density shows three undulatory levels, decreasing prog ressively from the city center to suburban districts.This regularity coincides with the gradient tendency of urban air pollution in the same area.2.The contents of sulphur and lead in the body of the scale insects and their host plant are much higher in the polluted districts than that in the relatively clear districts, and the highest values are up to 1.92 g/kg and 6.80 mg/kg respectively.The accumulative amounts of pollutants are positively correlated with the automobile number.3.Based on our study, it is sug gested that Eulecanium gigantea and E.kuwanai can absorb and tolerate pollutants and that is an important mark on their resistance to city pollution.Futhermore, other reasons which result in the increasing number of scale insect are also discussed from the point of view of biological chain "scale insect-host plant-natural enemy" in the paper.

Key words: Urban air pollution, SO₂ and Pb coccidae, Scale insect, Eulecanium gigantea, Eulecanium kuwanai, Sophora japonica