Dr. Dethier explains his research for the perfect insect repellent. He discusses and gives examples of the five qualities of a perfect repellent: odorless, inexpensive, non-toxic, cosmetically acceptable, and effective for extended periods of time. Using a diagram of a blowfly's anatomy, Dr. Dethier explains how the flies are used in repellent research. Then using a series of actual flies, their wings waxed to sticks, Dr. Dethier puts the feet of the fly successively into sugar water, .01% glycol and sugar, and .1% glycol and sugar to observe the fly's reaction. The result is generally the average of a 100-fly test. Dr. Dethier then shows how one can predict the feasibility of some chemical compounds as repellents by their composition. He constructs a graph and using aldehydes, plots the repellent effect in relation to the size of the compound's molecules.