346 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



Animal Ecology and Adaptations. The relation of animals 

 to their physical environment, and their inter-relations with 

 other animals and plants, constitute a special phase of biologic 

 study called animal ecology. As these special relations are 

 associated always with special adaptive conditions of structure 

 and function, the subject of ecology includes, in a way, the 

 subject of adaptations, and thus comes with particular perti-' 

 nence under the attention of the student of animal evolution. 



The relations and varied adaptations of animals in connec- 

 tion with food getting, defense and offense, production and care 

 of young, and similar other activities common to all animals 

 but performed in extraordinarily various ways, are most 

 stimulating subjects of investigation. As these adaptations 

 are functional as well as structural, such subjects include the 

 study of the behavior, instincts and intelligence of animals, and 

 become thus directly related to the problem of the origin of our 

 own instincts and intelligence. Among the various highly 

 developed special adaptations of animals those of color and 

 color pattern, of parasitism, and of different phases of mutual 

 aid, offer unusually interesting subjects of special study, and 

 may be introduced here by a few paragraphs. 



Color is produced by the presence of pigment in the surface 

 parts or by the structural character of the epidermal hairs, 

 feathers, or scales with which the animal's body may be 

 covered. By reflection and interference effects, due to the 

 laminated or striated structure of these parts, brilliant metallic 

 or iridescent colors are produced, such as the blues, purples and 

 greens of the humming-birds, butterflies, fishes, etc. The 

 most obvious use of the colors depends largely upon their 

 arrangement into definite patterns and on the harmonizing of 

 these color patterns with the environment in such a way as to 

 make the animal more or less indistinguishable when at rest 

 and thus hide it from its enemies. The phenomena of pro- 

 tective resemblance and mimicry are among the most highly 

 developed and extraordinary of animal adaptations. 



Some of the many curious conditions of structure, develop- 

 ment and habit, developed in connection with the adoption of a 

 parasitic life have already been described in this book. 



