320 Mr. C. F. M. Swynnerton's Experiments 



is hungry, though Y, X, W, etc., refused in turn as he 

 fills up, to the few species (A) that are regularly eaten by 

 him at all stages right up to repletion-point. 



This fine grading in degrees of palatability was un- 

 expected — though Mr. Marshall's experiments had shown 

 that some grades might be looked for — and, starting with a 

 bias in favour of the " palatability" of most Nymphalinae 

 and Pierinae, I at first fought against it ; but I could not 

 long withstand the combined testimony of every animal I 

 experimented on. 



Fine gradation in palatability granted, with its corollary 

 that few species are at all times acceptable to all their 

 enemies, it was interesting to note its theoretical bearing. 

 This seemed to be, that there are probably few species 

 that do not sometimes require to be distinguished by an 

 enemy from such other species (or, an important and highly 

 explanatory consideration, from their own parent form) 

 as are at the moment acceptable to him. The selective 

 factors would be the unmistaken refusals and the mistaken 

 attacks of enemies, adult and otherwise (for I find that 

 even the former go on all their lives making numerous 

 mistakes and that they also tend to test specially anything 

 of unusual appearance). 



Yet distinctiveness and diversity are nearly as marked 

 in the eggs of Lepidoptera as they are in the fully de- 

 veloped insects that lay them.* These eggs are laid on 

 exposed surfaces liable (as I have many hundreds of times 

 seen) to the exceedingly close scrutiny of small warblers, 

 white-eyes and other minutely-searching enemies ; they 

 are often in contrast to those surfaces and are commonly, 

 even when not thus in contrast, distinctive; and this 

 distinctiveness is apparently in part for casual effect, for 

 it is absent from the hidden bases of the eggs, nor is it 

 approached by that of most underground eggs known to 

 me, the differences between which are merely such as 

 might naturally result from the fact that their parents 

 are different. I thought, therefore, that it would be inter- 

 esting to ascertain whether nauseousness — and graded 

 nauseousness at that — was present in leaf-laid eggs. 



I was very unlucky in my attempts to secure a suitable 



* I lay stress on distinctiveness — recognisability when detected — 

 rather than on conspicuousness, for I regard the latter as a purely 

 auxiliar}^ quality, though highly useful and likely always to be 

 selected so far as it can be safely carried. 



