cxxv 



of a number of distinct species of Planema. The two forms of 

 Hypolimnas duhius look like the two distinct species of Aniauris, 

 which are shown along with them on the slide. The females of 

 the Chalcosiinae often bear a close resemblance to butterflies, 

 while the males are quite different, for instance the female of 

 Cyclosia Jiecahe might easily be mistaken for the Pierine Terias 

 hecabe, and the female of Cyclosia papilionaris for a Danaine 

 butterfly. Many other instances of such resemblances between 

 synpatric species have been exhibited at our meetings. If we 

 compare this kind of daylight di- and polymorphism with the 

 kind of differences obtaining in night-flying Lepidoptera, in 

 which evolution tends to produce a resemblance to dead leaves, 

 lichens, twigs, pebbles, etc., the three-fold coincidence of (1) 

 daylight, i. e. visibility, (2) sharply marked and conspicuous 

 di- and polymorphism, and (3) resemblance to synpatric 

 species, forms such a striking contrast that nobody can 

 seriously maintain it to be due to pure accident. There must 

 be some connection betv/een the three concurrences ; we 

 require an explanation ; we cannot look upon these facts as 

 merely curious; and the* explanation most satisfactory and 

 which faces the facts squarely is that given by Natural Selection 

 acting on the varieties produced by the influence of the physical 

 conditions (in the widest sense) of the environment, however 

 strong the modern and popular tendency may be to decry 

 Natural Selection as a factor in Evolution. 



We now come to the second kind of variation which no 

 field-entomologist can have failed to observe who has ever 

 collected in two different faunistic districts, such as Scotland 

 and the South of England, or Central Europe and the Medi- 

 terranean countries. We have seen here exhibited many 

 illustrations of geographical variation, with regards to tropical 

 countries particularly from the collections of Mr. Joicey and 

 Mr. Kaye. A collector passing from one district into the 

 geographically nearest but faunistically different country, 

 will meet with many familiar species which, however, to him 

 as an expert have an unfamiliar appearance ; they are the old 

 friends, but with a difference. Let us take as an example the 

 Lepidoptera of Great Britain and Ireland. We read in 

 Wallace's " Distribution of Animals," in the chapter on the 



