MIMICRY AND MELANISM 185 



It is well known that all four species (including 

 philenor) fly together. Even in my own limited 

 experience I have taken three of them in adjacent 

 streets on the outskirts of Chicago on the same 

 day (Aug. 10, 1897), and the fourth in the same 

 locality a little earlier (July 28). But precise 

 knowledge of their relative proportions in different 

 parts of their range would be of high interest. 

 Again, troilus extends to the North- West Territory 

 of Canada, probably far beyond the area in which 

 philenor occurs as a straggler ; and it would be 

 very interesting to compare minutely large num- 

 bers of such specimens with those from districts 

 where the model is dominant. A similar study 

 should be made of the Canadian specimens of 

 asteritis, although this species does not extend 

 so far beyond the northern limits of the poison- 

 eating model. 



From another point of view the interbreeding 

 of the turnus female of glaucus with a male from 

 some northern district where turnus is unknown or 

 very scarce would be of the highest interest. 

 We should here be able to test whether the 

 Mendelian relationship exists between the parent 

 form and its partially melanic variety further 

 transformed by selection, not a mere melanic 

 ' mutation '. I trust that my friend Prof. C. B. 

 Davenport may be able to undertake this experi- 

 ment at the Cold Spring Experimental Station. 

 I cannot doubt that breeding could be easily 

 carried through two generations in a large enclosed 



