NO. 7 



PROTECTIVE ADAPTATIONS McATEE 



141 



Weiss' table summarizing these interesting data is substantially 

 (juoted as follows : 



Num- 

 ber of 

 species 



Phyto- I Sapro- 



phag- phag- 



ous. ous. 



Per Per 



cent cent 



Har- 

 pacto- 

 phag- 

 ous. 

 Per 

 cent 



Para- 

 sitic. 

 Per 

 cent 



Pollen 

 feeders, 

 misc. 

 species. 

 Per 

 cent 



Quelpart Island 



Western Arctic Coast of N. A. 



State of N. J 



State of Conn 



The similarity of the figures whether for the States of New Jersey 

 or Connecticut, for the Pacific Coast of Arctic America, or from far 

 flung Quelpart Island (Corea) shows that there is at work some 

 principle controlling choice of food that overrides whatever efifect the 

 so-called protective adaptations may have. 



It is almost certain that the constancy of the ratios is due to a 

 tendency (one might well say a compulsion) toward distribution of 

 predatory and parasitic attack. This distribution is one that lays every 

 group under tribute, that takes toll from each so long as the tax is 

 more easily collected there than elsewhere, but when that condition 

 fails turns toward more easily available supplies. 



Predation is thus kept proportional to population and practical 

 indiscriminancy as to factors other than availability must result. 



Indlscriminancy of Natural Check.s other than Predator.s 



It will not be ciuestioned, we believe, that from the standpoint of 

 protective adaptations such checks as parasites, bacterial and fungal 

 diseases, heat, cold, and other climatic factors, are indiscriminate in 

 action. 



Relative Importance of Natural Checks 



Years ago Chittenden writing of " Insects and the Weather " ' 

 stated : " It also appears to me what has been observed by Mr. Marlatt 

 in the case of scale insects .... is true in general, viz., that favor- 

 able or unfavorable climatic conditions are of greater importance in 



* Bull. 22, n. s., U. S. Div. Ent., pp. 51-64, 1900. 



