[Objectives]  To investigate the effects of feeding Brontispa longissima coconut leaves at three different growth stages on their growth and development. [Methods]  Groups of B. longissima were fed either unopened coconut fronds, half-opened fronds or opened fronds, and differences in their developmental duration, fecundity and population trend index were measured and compared. [Results]  There were significant differences in egg length and pupal weight between B. longissima that were fed unopened fronds compared to those fed opened fronds. Larval development periods were 41.45 d for B. longissima fed unopened fronds, 40.61 d for those fed half-opened fronds and 36.38 d for those fed opened fronds. The pre-oviposition period of B. longissima fed on unopened fronds was significantly shorter than that of those fed half-opened fronds or unopened fronds. The highest average fecundity (161.78) was recorded in B. longissima fed half-opened fronds, the second highest (147.33) in those fed opened fronds and the lowest (112.60) in those fed unopened fronds. The population trend index of B. longissima fed unopened fronds, half-opened fronds or opened fronds was 24.79, 35.86 and 45.94, respectively. [Conclusion] The growth stage of coconut leaves provided to B. longissima had a significant effect on the growth and development of this species. B. longissima fed opened fronds had the shortest developmental period, the highest survival rate and the highest population trend index. Opened coconut fronds are a more suitable food than unopened or half-opened fronds for B. longissima.