NO. 7 PROTECTIVE ADAPTATIONS McATEE I43 



of the groups can play only minor roles in the whole drama of pre- 

 dation, and that insects must occupy the center of the stage, regardless 

 even of the superior individual size of the chordates. 



To put the case in other language we may quote from David Sharp/ 

 " Insects form hy far the larger part of the land animals of the 

 world ; they outnumber in species all the other terrestrial animals 

 together, while compared with the vertebrates their numbers are 

 simply enormous " (p. 83). 



" Insects derive their sustenance primarily from the vegetable king- 

 dom. So great and rapid are the powers of assimilation of the Insect, 

 so prodigious its capacity for multiplication, that the mammal would 

 not be able to compete with it were it not that the great horde of six- 

 legged creatures has divided itself into two great armies, one of 

 which destroys the other " (p. 521). 



SUMMARY 



The hypotheses about protective and warning colors and mimicry 

 are part of the Natural Selection group of theories. These coloration 

 phenomena and other protective adaptations are supposed to have been 

 developed and perpetuated by the selective value they had in shielding 

 their possessors from attack by predators. 



Preceding sections of this discussion call attention to the evidence 

 that one group of predators after another is known either to prey 

 habitually upon " specially protected " groups, or to be so largely 

 guided in choice of food by availability as practically to ignore pro- 

 tective adaptations. 



The former is admitted to be true of dragonflies, robber flies, 

 mantids, predacious locustids and Hemiptera, parasitic insects, and 

 of spiders, while the latter is stated to be characteristic of the aquatic 

 immature forms of mayflies, stoneflies, caddisflies, and two-winged 

 flies, and of fishes. Data cited throughout the main body of the 

 present paper show a high degree of indiscriminancy also on the part 

 of amphibians and reptiles. 



In fact this general indiscriminancy on the part of predators is so 

 evident that even ardent advocates of the selection theories have been 

 impressed by it and one of them, G. A. K. Marshall, in a paper on 

 the " Bionomics of South African Insects " says : ^ 



If the view advocated by many, that birds cannot be reckoned among the 

 principal enemies of butterflies in the imago state, be true, then I consider that 

 we may practically abandon the whole theory of mimicry as at present applied 

 to the Acraeinae and Danainae of Soutli Africa at all events, for from what I 



'Cambridge Nat. Hist., vol. 5, 1910. 

 "Trans. Ent. Soc. London, 1902, p. 356. 

 10 



