Abstract: Among the three major factors of efficient producing chinese gallnuts,some mosses as the winter hosts of the gall aphids play a decisive role.This paper reports the results of an investigation on selecting the moss as the most suitable winter hosts of the horned gall aphids,Schlectendalia chinensis(Bell),and a preliminary study on its natural resources in Fengdu County,Sichuan Province,which was done from October 1990 to April 1991.The three species of the moss Plagiomnium maximoviczii(Lindb,) T,Kop.,Plagiomnium maximoviczii Lindb.var.emarginatum Chen ex Li et Zhang and Plagiomnium acutum(Lindb.) T.Kop.were recognized as the most suitable winter hosts of the horned gall aphids in Fengdu.Before the gall aphids migrate from the moss to the summer host trees in spring,as in the case of artifical planting moss-plate,the average number of the living overwintering nymphs of the first two species of the winter host moss amounts to 18469.4 and 10375.0 per m² respectively,in the case of natural growing winter host moss,the average number of the nymphs on the three species of the moss mentioned above amounts to 3163.4,5124.7 and 3395.7 per m² respectively.These three species of the moss usually grow at the wet locations in Fengdu,i.e.on the surface of the wet soil or rocks,and under the humid fir woods or other kinds of the evergreen woods.The host moss is widely distributed,and often grows in large patches especially at the south bank of Yangtze River in Fengdu.The natural resources of these three species of the host moss are rich in Fengdu County,and these offer good developing bases for producting chinese gallnuts.