The use of olfactory repellents, especially against biting insects, is an important protective measure. It is also a matter of common knowledge that certain insects are able to locate their mates or their prey largely through the agency of attractive scents. Concerning these latter, Dethier remarks that, “we recognize the fact that no one attractant alone performs the service of guiding an organism to its proper habitat, or mate, or food. The desired end is achieved by a complex array of stimuli working in harmony. In chemical attractants, however, one finds precision guidance. The action of others, as light, temperature, humidity, is comparatively gross, approximating as it does usually, a vicinity. The extreme value of chemical attractants to an organism lies in the specificity and accuracy of operation.” (1).