Using the model organism Drosophila melanogaster, I sought to investigate whether naïve insects can utilize genes related to detoxification in the response to insecticides and the roles those genes have in insect physiology. This began with an analysis of the transcriptional response to several insecticides and the synergist PBO. I found that none of the insecticides elicited a transcriptional response, but there is a robust upregulation of genes related to detoxification and lipid metabolism after cytochrome P450 (CYP) inhibition via piperonyl butoxide (PBO) exposure. This response is concentration- and time course-dependent, but is independent of genetic background, diet composition, and microbiota. Perhaps most interestingly, genes responding to PBO exposure follow tissue-specific patterns with some being expressed all over the body and others showing distinct patterning in the digestive tract. I next investigated genes in the UDP-glycosyltransferase (UGT) and ATP-binding cassette (ABC) transporter families for their effect on the response to insecticidal compounds. This led to the discovery that Ugt35B1 is the principal enzyme responsible for nicotine glycosylation, a function not known before. I confirmed the activity of this enzyme through LC-MS of Ugt35B1 knockout and control flies and also showed that it can glycosylate the structurally similar compound flonicamid but not imidacloprid. Finally, my investigation of UGTs and ABC transporters revealed that the previously undescribed transporter vitalporter (CG3164) is required for development and survival of Drosophila. When knocked down, larvae do not survive development, pupae do not properly eclose, and adults die off more quickly than controls. This effect is most prominent when knocked down in the brain, meaning there is likely a necessary function that vitalporter plays in the nervous system. Together, these results reveal that Drosophila melanogaster does not use detoxification enzymes in the response to insecticides, and that some genes related to the detoxification of xenobiotic compounds play important roles in the normal physiology of insects as well.