Larvae expressing ppk^{S551V.Scer\UAS} under the control of Scer\GAL4^ppk.1.9 display premature and enhanced intermediate surfacing transition (IST) behavior (emerging from the food transiently to to roam the food surface, prior to complete food exit) compared to wild type. This phenotype is unaffected by a ppk null mutant background (Df(2L)ppk1Aid/Df(2L)ppk1MirB). The mutant larvae also display a premature shift in thermotactic preference behavior (wild type larvae change the way they respond to temperature changes when they go from feeding to wandering) compared to wild type. However, eventual food exit does not occur significantly later than in controls. The resulting adult flies are smaller in size than their wild type counterparts.