Practically everyone is aware of the widespread fear of snakes exhibited by people of all races and in all walks of life. This fear although largely emotional, is rationalized by many persons with the statement “Well, it MIGHT be poisonous.” Other persons believe that there is some rule of thumb, such as a flat or triangular-shaped head, by which all poisonous snakes may be recognized. A great many persons kill all snakes, just on general principles. Thus the innocent suffer with the guilty, the harmless with the dangerous. As scientists explore deeper and deeper into the intricacies of animal behavior and obtain more and more knowledge of the ecological relationships among animals and between animals and plants, it becomes increasingly clear that these relationships present a delicate balance or adjustment of nature. Epidemic diseases, disasters such as fires and floods, and radical climatic changes may upset or alter these relationships, sometimes with far-reaching effects. But the greatest and most persistent disturber of the biological peace is MAN. Almost every time man reduces or destroys one phase of nature, he releases, in so doing, previously unrecognized forces which turn on him in a manner that he least expects. Snakes, in general, live on small rodents, thereby helping to maintain a balance whereby rodents are unable to increase to such a point that they get out of nature’s control. Kill all of the snakes in a given area, and some of the control on rodent population is removed with a resulting increase in the destruction of vegetation and consequent damage to farmers’ crops. So if you must kill snakes, by all means limit your activities to those which are known definitely to be poisonous. One of the purposes of this booklet is to familiarize the desert dweller or visitor with the snakes that ARE poisonous. All the rest are harmless, in fact they are generally beneficial to mankind, even though their heads may be triangular in shape. A given territory is capable of supporting a rather definite number of snakes. Kill the harmless ones and those that come in to take their place may be poisonous species. In all parts of the country certain creatures, particularly reptiles, are credited with supernatural powers for causing injury or aid to human beings. Among aboriginal peoples, these superstitions are a part of their religion and have a powerful effect upon their thinking. For example, among the Hopi Indians of northern Arizona, snakes may be messengers who, if properly indoctrinated, will convey to the rain gods expressions of the people’s need for moisture in order that their crops may mature. Even among a people who for years have had the benefit of scientific knowledge, superstitions persist. The hoopsnake and the milksnake offer cases in point, and there will be readers of this booklet who will toss it aside in anger because it states that both of these myths are without substantiation in fact.