Population development of Aculus schlechtendali (Nalepa) (Acarina: Eriophyidae) was investigated in three different locations (Kecioren, Besevler and Kalaba) in Ankara, on Malus floribunda L. (Rosasacae) during 2004 - 2006 years. Two-year of observations revealed that A. schlechtendali individuals were hibernates in deutogyne stage in the crevices and hiden places of the trees. They began to move to the blossoms of the plants at the beginning of may. Deutogynes laid their eggs on the feeding place of the youngs. In general higher eriophyoid protogyne populations were observed during May and June all three locations of the study area. The data show that the deutogyne population reached its peak by the end of May and after this, the deutogyne population levels become lower whereas protogyne population showed small rate of increas around the same time but reached its peak by mid June. Deutogyne population has been seen in low population density during the summer months. During surveys on predators of Aculus schlechtendali two phytoseiids, one stigmaeid, and one tydeid mite species, and 14 Cocinellidae species were recognized as natural enemies. Beside this, taxonomic characteristics and distribution of this eriophyid species were indicated.