What kind of insect is a purple long tail that is not called a slug?

According to the query of the Animal Encyclopedia, an insect with a long purple tail that is not called a slug may be Lagerstroemia indica. Coccidia Lagerstroemia belongs to Homoptera and Coccidae. Scale insects have become important pests of garden plants in East China and Central China, especially in Nanjing, Wuxi, Taizhou, Wuhan, Danjiangkou, Nanyang, Meizhou and other places in the Yangtze River valley, which have different degrees of occurrence and harm every year.

The nymphs and female adults of Lagerstroemia speciosa mainly gather on the twigs of Lagerstroemia speciosa which are more than 3 years old to suck juice. After the shoot is killed, the leaves on it turn yellow and fall off, which makes the growth of the tree stagnate, the tree wither and even the whole plant die.