SINGLE-GENE conditional mutants of Drosophila melanogaster which affect both development and the physiology of the adult present a valuable opportunity for studying the effects of a specific biological lesion on both individual physiological processes, and on whole animal biology encompassing the growth and development of the organism. Temperature-sensitive mutations at the shibire locus of D. melanogaster produce both developmental and neurophysiological defects during various periods of the animal's life cycle, and thus illustrates how a single gene product can participate in both synaptic transmission in the adult as well as in the process of differentiation during development. The importance of analysing such a mutant lies in the hope of revealing a biological mechanism common to both adult physiology and the developmental process. Such a revelation might contribute insights into both processes. The work presented here is an analysis of the adult physiological phenotype of the shibire mutant.