The relationship between worker body mass and age in stingless bees is an important aspect of morphological development that is poorly understood. In this work, we examined the body mass-age relationship in workers of the stingless bee Melipona quadrifasciata. Newly emerged workers (n=151) were marked and weighed and then returned to their nest, after which body mass was monitored for 45 days. Melipona quadrifasciata workers showed a substantial increase in body mass during the first five days of life in the nest (F_5,190=146.91, P<0.001) that most likely reflected the extensive glandular and ovarian development during this period. From the 6th to the 24th day, there was a gradual decrease in body mass (F_12,183=10.32, P<0.001) that continued after the 25th day (F_13,327=5.94, P<0.001) before eventually stabilizing (F_17,127=0.35, P=0.99). The decrease in body mass with age probably reflected the greater participation of workers in processes associated with provisioning and oviposition, as well as the preference of workers to donate rather than receive food during trophallaxis and at the beginning of foraging activity.