CXXTill 



counteract such one-sidedness by emphatically stating again 

 and again that the variation of the species from district to 

 district is the rule and not the exception, and it appears to me 

 appropriate that a protest should be uttered from this place, 

 because Entomology plays such an important part in the 

 elucidation of the problems of life. 



Every Entomologist with a little experience is aware that 

 in any district where there is no physiographical barrier 

 preventing a promiscuous interbreeding of the specimens of a 

 species, the community of individuals may be practically 

 uniform or may be variable, there being a gradation from 

 uniformity as the lower extreme to polymorphism as the upper 

 extreme. The diversity between the groups of individuals 

 of polymorphic species is frequently so great, and the differences 

 are often so sharply defined, that in many instances the 

 varieties have been mistaken for species until their true status 

 was discovered. The variation is either independent of sex, 

 or is sexual or partly sexual. Papilio clytia from India with 

 a striped and a brown form in both sexes may be taken as 

 an example of non-sexual dimorphism; Hypolimnas dubius 

 wahlbergi from South Africa is sharply dimorj)hic ; and 

 Papilio lysithous is trimorphic in Rio Grande do Sul and other 

 parts of South-east Brazil. Sexual dimorphism goes often 

 very far in Lepidoptera. The wingless females of Psychidae 

 and some other Heterocera may be mentioned as one extreme 

 development, but equally striking are the differences in the 

 shape and colouring of the wings in numerous other Lepido- 

 ptera, of which some species of Troides, Papilio, Planema and 

 Argema here shown may serve as examples. Very often each 

 sex appears in one form only; in many instances, however, 

 one sex or both are split up into two or more forms; this is 

 frequently the case among Papilionidae and Nymphalidae 

 {Papilio memnon, P. polytes, P. rumanzovia, P. androgeus, 

 etc. ; Hypolimnas, Hestina, Charaxes, etc.). Common as the 

 phenomena of di- and polymorphism are in Lepidoptera the 

 distribution of the different kinds of variation among the 

 various families is by no means uniform, there being several 

 points in its occurrence that appear to me of some interest. 

 The strong reduction or loss of the wings occurs only among 



