Silkworm larvae were fed on the leaves of four mulberry trees)Morus nigra and three different varieties of Morus alba (Indian, Balady and Romi) ) soon after hatching (newly hatched larvae) and during the larval stage. The results revealed that the maximum body weight of larvae occurred in larvae fed on leaves of M. nigra being 3.071 g. The larval duration was prolonged to 29 day in larvae fed on M. nigra and M. alba Indian, leaves. While the larval duration was 27 and 25 day inlarvae fed on M. alba Balady and M. alba Romi, respectively. The maximum total weights of consumed and digested leaves by larvae (third, fourth and fifth instar) were 18.104g and 6.451g when larvae fed on leaves of M. nigra, respectively. The maximum efficiency of conversion of ingested and digested food to body substance in fifth instar larvae was 21.24 and 66.47% when larvae fed on leaves of M. alba Romi, respectively. On the other hand, The minimum efficiency of conversion of ingested and digested food to body substance in fifth instar occurred in larvae fed on leaves of M. nigra, (14.87% and 42.95 %, respectively). The maximum weight of fresh and dry cocoons was found in larvae fed on leaves of M. nigra, (1.449 and 1.305 g, respectively). The maximum length and weight of silk filament occurred in larvae fed on leaves of M. nigra, (1146 m and 0.23 g, respectively). The highest number of laid eggs was 420.7 occurred larvae fed on leaves of M. nigra. According to the chemical analysis, Percentage of total carbohydrate, protein, phenols as gallic acid and crude fibers (3.1916%, 21.00%, 1.168 % and 13.74%, respectively) were higher in leaves of M. nigra, than leaves of M. alba.