GORDON, S.D.*; STEVENSON, R: Long-term Mass Gains relative to Meal Size and Sugar Concentration in Two Species of Butterflies, Pieris rapae and Manataria maculata

We investigated how the concentration of sugar in artificial nectar affects meal size and changes in body mass of Pieris rapae, a widely dispersed common Pierid species captured in Boston, MA and Manataria maculata, a long-lived fruit eating tropical Satyrine species captured in Monteverde, Costa Rica. Butterflies were kept in laboratory cages and had limited opportunity for activity. The initial mass (mg) and wing length (mm) were recorded for each individual. On a daily basis, five (Pieris) or six groups (Manataria) of 5-7 individuals were fed specific sugar water concentrations ranging from 0 to 50% by weight until satiated. Body mass was recorded both before and after feeding. Groups offered pure water took in the smallest meal sizes averaging about 5% of their body mass. In contrast, the groups fed at approximately 10% took in the largest mass per meal, averaging 16% for Pieris and 55% for Manataria. At higher sugar concentrations, meal size declined in both species, however groups fed between 40% and 46% took in the largest amounts of sucrose per meal. Over the duration of the trials, groups fed between 38% and 40% sugar water gained the most weight, roughly 85% for the Pieris (20 days) and just under 13% for the Manataria (7 days). Both the species that fed on water alone lost mass. The results address ecological implications (water balance, metabolic rate, condition indices) and raise questions about physiological limitations (meal size, long term mass gain) for each species.