The omnivorous leaf roller,Platynota stultana(Walsingham), was reported to have five larval instars. Careful observation of larvae reared at various temperatures showed that all males and some females underwent five larval stages. Other females passed through a sixth stadium at all temperatures. The frequency of females with six instars was lowest at 25°C and increased as rearing temperatures approached extremes. Head-capsule width in both sexes was affected also by the temperature at which the larvae were reared. Generally, head-capsule width decreased significantly when the rearing temperature exceeded 30°C.