124 ECOLOGICAL FOUNDATIONS OF ZOOGEOGRAPHY 



Artemia salina. The resistant nature of Cyclops fimbriatus is shown 

 by the variety of situations which it inhabits. It is found in Greenland 

 and Ceylon, on the plains as well as on Mount St. Bernhard. It occurs 

 in concentrated mineral waters, in iron-ochre deposits of brooks, and 

 in caves and mines. 9 



Euryphagy is frequent in widely distributed forms. The food of 

 carnivorous animals is least restricted, since mammals, birds, and 

 fishes, and even insects, worms, and mollusks, are much more uniform 

 in chemical composition than are leaves, fruits, seeds, or other parts of 

 plants. Thus the most widely distributed mammals next to the bats 

 and marine forms are the carnivores such as the Eurasian wolf, with 

 the closely related North American wolf ; the leopard, ranging through 

 Africa and south Asia into China and Borneo; or the puma, whose 

 range extends from Alaska to Patagonia. Both nocturnal and diurnal 

 birds of prey may have a very wide range — so the sea eagle, the 

 peregrine falcon, and the barn owl. The extraordinary euryphagy of 

 the raven, which feeds on carrion and on living animals from roe- 

 fawn and birds to insects and worms and fish, birds' eggs, plants and 

 seeds, must have had an important effect in giving it its wide dis- 

 tribution. 



Euryphagy has plainly furthered the spread of herbivorous insects. 

 The caterpillar of the nearly world-wide cotton bollworm Heliothis 

 armigera feeds mainly upon the tobacco plant at Delphi, on maize in 

 Java, and on the cotton plant in North America. 10 The caterpillar of 

 the widespread Utetheisa pulchella is no less catholic in its food habits, 

 and also displays a high degree of tolerance toward climatic differ- 

 ences. 11 Helix aspersa, transported by man to all parts of the earth, 

 has unquestionably been able to establish itself on account of its 

 euryphagy. This species ate 114 out of 197 different food plants offered 

 to it, as compared with 54 eaten by the more restricted Helix hortensis 

 and only 26 by H. nemoralis. 12 On the other hand, animals which are 

 limited to restricted environmental niches where food is scarce, as in 

 mountain torrents, tend strongly toward euryphagy. 



Limited range, especially for species and genera, is, on the whole, 

 a much more general phenomenon than wide distribution. Specializa- 

 tion, i.e., the exact inherited adaptation to given habitat conditions, 

 affords so many immediate advantages that specialized species usually 

 win in the struggle for existence. An adaptable organization is not 

 necessarily superior; its advantage lies primarily in the capacity for 

 wider distribution. The fatality in specialization lies in the corre- 

 sponding loss of the capacity for adaptation. The disadvantages of 

 adaptation to a special habitat appear only when the habitat condi- 



