MICHIGAN ACADEMY OF SCIENCE. 5S 



regularly upon mammals and birds, and species of large size. The king 

 snake, Lampropeltis doliatus triangulus, is the only snake found in this 

 region, reported to feed upon mammals and birds regularly (Ditmars. 

 1908, p. 344; Ruthven, Thompson and Thompson, 1912, p. 111); and 

 the king snake and the watersnake are the only ophidian species wliicli 

 attain the length of 40 inches or more. Large species like the black 

 snake, Bascanion constrictor, are not included in the Douglas Lake fauna. 

 The entire series of amphibians and reptiles known to occur in the 

 Douglas Lake region may be summarized as one of rather few species, 

 the reptilian members of which are, in several cases at least, very near 

 the northern limit of their range. 



LOCAL DISTRIBUTION AND INTERRELATION OF SPECIES. 



In the following tables (2, 3 and 4) the distribution of the several 

 species of amphibians and reptiles of the Douglas Lake fauna is con- 

 sidered with reference to the habitats in which these animals were found. 

 Some of the habitats have been named according to the conspicuous 

 plant species of the plant association or assemblage occupying the 

 habitat so designated, for although the amphibians and reptiles con- 

 sidered do not feed upon plants to any extent, certain rather definite 

 relations were found between the local distribution of these animals and 

 that of the several plant assemblages. In the tables (see table 2) the 

 relative abundance of each species as ascertained by repeated collecting 

 in each habitat is indicated by letters. The distribution of each species 

 in the region is shown by the series of habitats in which it occurs. It is 

 to be remembered that these tables give tlie local distribution of the fauna 

 during the months of July and August only, that is the summer aspect 

 of the fauna. 



Reviewing the local distribution and interrelations of the ampliibians 

 and reptiles of this fauna two grades of species, primary and secondary, 

 based upon the relative abundance of the individuals of the several 

 species were recognized. The various species were grouped into three 

 ecological series according to the habitat preferences of the seven 

 primary amphibian species, Diemictylus viridescens, Rana pipiens, Rana 

 cantahrigensis , Rana clamitans, Rana catesheana, Bufo americaniis and 

 Plethodon erythronotus. This grouping was followed because it was 

 found that most of the species of reptiles sharing these habitats, were 

 either directly dependent for a considerable portion of their food upon 

 some of the seven primary amj^liibian species, or were partly or indirectly 



