The sense of smell, or olfaction, plays a critical role in the behavior of various animals. This is true for disease-transmitting insect vectors, including mosquitoes, which use odorants, like carbon dioxide, to find their hosts. We study the fruit fly, Drosophila melanogaster, to elucidate the mechanisms by which neural circuits control olfactory behaviors. In the experiments discussed here, we examined the Drosophila melanogaster wnt5 mutant, which we have previously identified as a neurological mutant for its response towards carbon dioxide (a repulsive odor) and apple cider vinegar (an attractive odor). Data were collected by presenting wild-type and wnt5 mutant flies with either a choice of carbon dioxide and air, or apple cider vinegar and water. While wild-type animals significantly chose vinegar over water, but air over carbon dioxide, wnt5 mutant animals showed no significant difference in their choice between the neutral odor and either experimental odor. We conclude that wnt5 mutant animals were unable to discriminate between neutral odors and experimental odors, probably as a result of defects in their brain circuits.