The biology ofSylepta derogataFabricius was studied in the laboratory. The number of larval instars varied from 5 to 6 when fed singly. The larva possesses three pairs of thoracic legs and four abdominal prolegs. Among morphological differences between the instars, the most striking between the 1st and 2nd instars was the presence on the 2nd of two brown spots on the dorsal aspect of the prothoracic segments. Other instars were differentiated by the size and shape of the shields. The pupa is obtect and conical in shape with ten abdominal segmants, distinctly separated except the 9th and 10th segments. The genital pore occurs ventrally below the 8th abdominal segment in the female and in the male on the 9th segment. The abdomen of the male is more slender than that of the female. The life cycle was completed in 33.9 ± 0.5 days.