Although sand dunes devoid of vegetation are characteristic of the Sahara and some other deserts of the world, those of the United States support a variety of plant and animal life which, through generations of adaptation, are able to meet the conditions imposed by this environment (see frontispiece). Persons who misunderstand our deserts fear them, while others who have visited them become fascinated and return periodically or settle down and live in them. Some of the creatures living in deserts are known to be poisonous to man. Western thriller fiction of press, screen, and TV has emphasized and exaggerated this fact, developing in many people a wholly mistaken fear of the desert and its inhabitants. In contrast, other persons may under-estimate the possibility of injury from these animals and become careless. It is the purpose of this booklet to discuss accurately the various poisonous dwellers of the desert, as well as to debunk some of the superstitions and misunderstandings which have developed. A majority of the poisonous creatures in the desert are by no means restricted to that environment. Rattlesnakes, for example, so often associated with the arid regions of the West, occur in nearly every section of the United States. “A poison,” states _Encyclopedia Brittanica_, “is a substance which, by its direct action on the mucous membrane, tissues, or skin, or after absorption into the circulatory system can, in the way which it is administered, injuriously affect health or destroy life.” A poisonous creature may be defined as one which produces a poison for the administering of which it has developed a special mechanism. Since, due to personal differences, the bite or sting of a poisonous creature may injuriously affect the health of one person and not that of another, and since the poison of one individual creature may be insufficient to cause an unpleasant reaction, while that from several hundred might produce severe illness or even death, it is difficult to determine which creature should be included in a publication of this nature. The writer, therefore, has exercised his judgment in discussing in the following pages such creatures as he feels may offer a menace to the welfare of a visitor to the desert. In addition, a few paragraphs are included for the defense of several harmless desert dwellers which are mistakenly believed poisonous and which, as a result, have been mercilessly persecuted. [Illustration: _Giant desert centipede_] [Illustration: _Enlarged view of underside of centipede’s head, showing the double pair of jaws._ (Photographs by Marvin H. Frost Sr.)] It should be understood that the author has not himself conducted scientific research among the desert animals regarding which he writes. The material in this book is a digest of the findings of various competent scientific and medical authorities, and has been carefully checked for accuracy and authenticity.