( 171 ) 



XII. A7i attempt to point out the differential characters 

 of some closely-allied sj^ecies of Clirysomela, 

 principally those contained in Suffrian^s Wth 

 group ; also descriptions of some hitherto 

 uncharacterized forms helonying to the same 

 and other genera of the family. By JoSEPll 

 S. Baly, F".L.S. 



[Read June 4th, 1879.] 



(PL II.) 



My principal object in bringing the present paper under 

 the notice of the Society is to point out that Chrysomela 

 speciosa and its closely-aUied forms, belonging to the 

 11th group of Suffi-ian's monograph, possess good 

 structural characters, by the aid of which they may be 

 readily separated into their respective species. Hitherto, 

 owing to their great similarity in form, sculpture, pattern 

 and coloration,* these insects have been a constant source of 

 perplexity to the student, and are mixed up in our collec- 

 tions in apparently hopeless confusion. 



Since the promulgation of the Darwinian theory, the 

 ideas of most naturalists on the limits of a species have 

 been greatly enlarged, Avhilst their views as to its proper 

 definition have been much modified ; the conviction is 

 now almost universal, that in the diagnosis of an animal, 

 structural differences (as far as practicable) should be 

 insisted upon, to the comparative exclusion, beyond 

 certain limits, of the minor points of pattern, colour 

 and similar characters, formerly so constantly employed 

 for the purpose. 



Most animals, placed under favourable conditions of 

 life, \az., abundant food, genial climacteric influences, the 

 absence of enemies and the like, increase rapidly, and, 

 unchecked by natural obstacles, spread quickly over a very 

 wide area. Should these conditions be highly favourable 



* In the group before us the individuals of a species not only vary in 

 these respects amongst themselves, but the same colours and pattern arc 

 repeated in several closely-allied forms, so that, without strict attention to 

 structural differences, it is quite impossible to separate them. 



TIIANS. ENT. SOC. 1879. — PART II. (.JULY.) 



