plants and animals do not occur at random but are precisely located in their microhabitats. They live within the limits of their physical tolerance that is to say, they live only in that microhabitat to which they are adapted. Although this factor seems obvious, the physical and biological factors which govern distribution do not at first appear to be obvious. the collector must be cognizant of those physical factors which make up the habitat in which he will collect, know how those physical factors affect plants and animals and thus serve as permitting or limiting factors in distribution and also understand how these physical factors inhabit the metabolic or reproductive activity of those organisms he wishes to collect before he can predict where to collect. When the collector begins to recognize the physical factor or factors that dominate a given habitat and couples this with his knowledge of the habitat requirements of plants and animals, he will become successful in his endeavor