1909] Mimicry in the Butterflies of North America 241 



coast specimens were captured by Lord Walsingham, Dr. F. D. 

 Godman, and Mr. H. J. Elwes, and the geographical data are of 

 course as full and precise as we should expect or wish. 



I trust that my brother naturalists in America will make a 

 determined attack on the fascinating problems offered by the 

 phenomena of Mimicry in the North American butterfly fauna. 

 In this favoured part of the world the problems have been seen 

 to be sharp and clear as compared with the almost infinite com- 

 plexity of the tropics. If my assistance or advice be of any value 

 it is always at the service of those who desire to undertake such 

 investigations. 



It has been abundantly shown in the course of the address, 

 that immense numbers of specimens are required from the most 

 varied localities; and it is likely that difficulties may be presented 

 by the necessary manipulation, labelling, convenient arrangement 

 and permanent preservation for the study of future as well as 

 living naturalists, of so large a mass of material. I shall, how- 

 ever, be most pleased to undertake this part of the investigations 

 as regards all specimens accompanied by adequate data of space 

 and time. ' Such material, preserved in the Hope Department, 

 may be readily compared with the ever-increasing mass of exam- 

 ples illustrating the same principles in other parts of the world. 

 If the indications observed in a small series are still found to 

 hold in a large one, the growth of such a feature as the orange- 

 brown apex of the fore wing in Limenitis lorqiiini would be demon- 

 strated by a glance at its average condition in specimens from 

 the different localities as we pass from north to south. Further- 

 more, we might reasonably hope that a similar series collected 

 after an interval not greatly prolonged would exhibit differences 

 in average composition — the actual measurable evidence of the 

 evolution of a character in a species in the natural state. Even 

 though such evidence be left for our successors to witness, it still 

 remains our duty to provide them with the standard by which 

 alone they will be able to detect and measure it. But I am hope- 

 ful of more than this, and think it by no means unlikely that a 

 part of the reward may be reaped by a single generation of 

 workers. 



An excellent example of work done in a single locality, work 

 which now requires to be extended to many species in many 

 localities, is afforded by the data obtained by Mr. J. H. Cook, 

 and summarized in the following note. 



