NO. 7 PROTECTIVE ADAPTATIONS — McATEE 55 



Such is the actual condition of the pupal butterfly, but let us examine its 

 outer covering. It is a frightful-looking object, armored, and covered with 

 sharp spikes between which beady false eyes peer out. Tt is absolutely harmless 

 but appears otherwise. To birds it is doubtless a thing to beware of, yet one 

 tiny puncture of its brittle covering would reveal a delicious feast witiiin. 



Many insects are thus protected, ones tliat could not compete in any form 

 of battle. They are given immunity from attack because they could not ward 

 it off themselves. In the case of the transforming pupa, some such form of 

 protection becomes a necessity. A butterfly in the making is as helpless as the 

 egg from which it sprung, so Nature resorts to camouflage to terrorize the 

 destroyers of her children. (Insect beliavior, p. i68, 1919.) 



Aside from the fact that Vanessa pupae do not enjoy immunity 

 (see p. 62), we may well inquire whether birds are not Nature's 

 children just as much as the butterflies, and just as fully entitled to 

 be her beneficiaries ? 



Bird enemies. — Identihcation to species especially has lagged more 

 in the case of lepidopterous items of food, than in those of any of the 

 other larger orders of insects, due chiefly to poor condition of the 

 remains of adults, and to lack of knowledge of larvae. Unidentified 

 Lepidoptera exceed 2.85 times those in some degree identified, and in 

 considering the relation of the percentages of identifications to those 

 of the number of species of various groups, the former figures should 

 be multiplied by 2.85. 



In view of the very imsatisfactory distribution of identifications of 

 Lepidoptera to families ( over 70 per cent of the whole number being 

 merely as Lepidoptera), it would be of little avail to discuss the 

 relative importance of family groups as bird food. Rather it will be 

 better to treat the subject along lines of general interest already 

 developed, as the preference between larval and adult Lepidoptera, 

 the extent to which hairy caterpillars are eaten, and the relation of 

 birds to butterflies, the chief illustrations of mimicry theories. 



The question as to which is eaten most extensively, adult or larval 

 Lepidoptera, is easily answered in favor of the latter. As the table 

 shows 68 per cent of all records of Lepidoptera are for larvae, further 

 unidentified ; moreover, it is certain that the great bulk of specimens 

 identified to families also were larvae. Thus the Noctuidae deter- 

 mined were chiefly cutworms, the Geometridae were mostly loopers, 

 the Tineidae principally case-bearers, and so on. Caterpillars, not 

 further identified, were found from 50 to 100 times in the stomachs 

 of 23 species of birds ; from 100 to 200 times in 21 species; from 200 

 to 300 times in eight species (downy woodpecker, blue jay, red-winged 

 and Brewer's blackbirds, warbling vireo, black-capped chickadee, 

 hermit thrush, and bluebird) ; from 300 to 400 times in two species 



