In this paper a new species of Eriococcus and its biology are described. The holo-type specimens of and are preserved in Shanghai Institute of Entomology, Academia Sinica. The paratype specimens 2 and 2 are kept in Nanjing Technological College of Forest Products.Eriococcus nematosphaerus Hu et Xie sp. n. (Figs. 1-4)Adult female Body crooked in shape, about 2.4mm. in length. Antenna seven segments. Legs three pairs, well developed, the tarsus longer than the tibia, with a pair of setae inflated at the apex. Claw with a small tooth, with a pair of setae inflated at the apex. Thoracic spiracles two pairs. Anal ring well developed, with small tooth and with a pair of setae inflated at the apex. Anal lobe conical, with five setae and five small sclerotized tubercles. Dorsal setae, in four types. Tubular ducts in three types. Quinguelocular pores present on ventriarea.Adult male Body slender, about 1.32mm. in length. Antenna filiform, ten segments. Thoracic spiracles two pairs. Legs well developed, three pairs. Claw with a pair of setae at the base. Two long setae and a genital orgen at the end of the abdominal segment.Newly hatched larva Body elongate-oval in shape, about 0.50mm. in length, with broadest width about the metathorax, 0.24mm. Antenna six segments. Thoracic spiracles two pairs. Legs three’pairs, well developed. Anal ring with small apiracles and six setae. Anal lobe with four conical setae and with a long seta at its apex. Dorsal setae six rows. Quinguelocular pores present on ventral area.Hosts and distribution Phyllostachys pvbescens, Ph. glauca, Ph. praecox, Ph. pro-pinqua, Ph. nigra, Ph. viridis, Ph. rubella and Ph. nuda, in Jiangsu, Zhejiang and Anhui Provinces, China from April to June, 1978 to 1980.New species differs from other species of this genus in the following peculiarities: dorsal setae in four types, tubular ducts in three types, and small sclerotized tubercles on the anal lobe, etc.Eriococcus nematophaerus Hu et Xie reproduces two generations a year at Nanjing. It passes winter in the adult female. Each female lays 9-537 eggs. Larvas of the first generation occur in late April to late May. Larvas of the second generation occur in late July to early August. Incubative rate of eggs around 90%.