Mango defoliator (Cricula trifenestrata Helfer) has been emerging as the important pest of mango in recent times in West Bengal, India. In terai region of West Bengal it completes four generations in a year. All the developmental stages were found to vary significantly over seasons. The total larval period was found 36.40 days to 45.30 days. Pupal diapause was recorded during summer and winter. Wide variation in male and female pupal period was recorded (24.40-89.40 days and 25.74-93.20 days respectively). The life cycle was completed in 77.00-146.00 days; depending upon the duration of pupal period in different generations. Temperature and RH gradient played significant role in the different life stages. The pupal stage has been identified as the most critical stage of the development of the species which determines the number of generations to be completed in a year and thereby intensity of infestation and crop loss caused by the pest spp.
