24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



O. F. Cook, says : ' " Prussic acid and other corrosive secretions 

 .... render .... the millipeds distasteful to birds and other animals 

 that might prey upon them." This statement implies that millipeds 

 have no natural enemies, an Utopian condition that probably no 

 animal enjoys. In fact the evidence here adduced shows that milli- 

 peds and centipeds as well, have numerous effective bird enemies, 

 which together with special enemies in other groups, no doubt prey 

 upon them about in proportion to their availability. From the com- 

 paratively small numbers of myriapods and their secretive habits, it 

 could not be expected that they form a very high percentage of the 

 food of carnivorous animals. This reasonable expectation certainly 

 is fully satisfied by the showing here made of the activities of their 

 natural enemies. 



Insecta (Insects) 



From tabulations appearing earlier in this article, it will have been 

 noted that arthropods contribute more than 88 per cent of all the 

 records of the animal food of nearctic birds and insects more than 

 90 per cent of the arthropods. To repeat the figures for the latter 

 group, insects furnish 190,919 identifications, which is 90.5891 per 

 cent of those of all arthropods. The percentage of species of the class 

 Insecta among the whole number of arthropod species known is 

 91.8589. 



Not only are insects the most numerous class of jointed animals, 

 and the most important item of the animal food of birds, but they are 

 also the group about which most has been written in a theoretical way 

 as to protective adaptations (especially color) and as to the relation of 

 these adaptations to predatory foes. On all these accounts it is de- 

 sirable to discuss the insects in greater detail, certainly in most cases 

 by orders and in some instances by families. Tabulations have been 

 prepared, therefore, showing numbers of identifications by orders and 

 families, with their relative percentages. The first of these is a 

 distribution of the total number of identifications by orders. 



The reader may have wondered why some of the tabulations as 

 to relative numbers of insects have not been based on the inventories 

 of some of the larger museums. However, this matter has been con- 

 sidered and the invalidating factor in such statistics is that such col- 

 lections are always more or less specialized either as a result of 

 policies of the museum or of the receipt of collections from special- 

 ists. Thus among insects, such favorite groups of the amateur as 



' Proc. U. S. Nat. Mus., vol. 40, p. 625, 191 1. 



