The present paper concerns the movement pattern of Aspidiotiphagus citrinus (Craw) on the surface of citrus leaf and its effect on host-finding. Movement pattern was determined by measuring the speed of movement and angle turned by the parasite. One-second time intervals were marked on paths taken by the parasite in three different areas of leaves infested with female larvae of Unaspis yanonensis (Kuwana) at the temperature of 25℃. The parasite moved in widely curving line in the interveinal area and moved straight on the central vein and leaf margin. Path taken by the parasite on the central vein was longer than on the leaf margin. After oviposition the speed of movement decreased and angle turned increased. Such changes lasted for about 10 seconds. During this period the parasite scarcely left the central vein and leaf margin. When a single parasite was liberated on a leaf surface where each ten individuals of the host were located artificially at intervals of 5mm in three areas mentioned above, the parasite encountered frequently hosts on the central vein. However, no difference was found in percentage parasitism of female larvae among three different areas of leaves collected in an orchard. This suggests the possibility that the parasite discriminates parasitized and unparasitized hosts.