BY THE REV. T. BLACKBURN. 55 



which follows is the result of a good deal of study and not a few 

 uasuccessful attempts to produce a satisfactory tabulation. As 

 regards colour, I am afraid it is as nearly as possible useless for 

 classificatory purposes. There is no species of which I have seen 

 numerous specimens that I have not ascertained to be variable in 

 respect of colour. Nevertheless, my observations certainly go to 

 show that the absence of all colour from particular parts of the 

 body is clearly specific. I know no species, e.g., having the 

 pi'othorax or undersurface generally of brilliant metallic colours, 

 but occasionally varying by the absence of those colours, nor any 

 vice versa — with the one exception that, as far as I have seen, I 

 should judge most species to be liable to the loss of colour from 

 the whole body — so as to be entirely black. I think, too, that 

 the direction of the colouring on the elytra is very little variable, 

 the different colours running in well defined longitudinal vittse 

 (e.g.) being a fairly reliable character. I have, however, made 

 very little use of colour in characterising species. 



The main difficulty, as visual in classification, I have found to 

 be the selection of characters for the principal divisions, whatever 

 character is selected appearing to be feebly defined yet not quite 

 wanting in a few intermediate forms. After several abortive 

 attempts to divide Chalcopterics into two main groups, I have 

 found that the most workable character for the purpose is the 

 presence or absence of a sulcus bordering the internal or antero- 

 internal margin of the eye. Nearly all the species have either no 

 sulcus at all or a very strongly defined one ; nevertheless, there 

 are a few in which there is a feeble indication only of this "ocular 

 sulcus," and I have found it necessary in adopting this character 

 as the main classificatory character of the genus to indicate by a 

 special mark in the tabulation certain species (placed among those 

 in which the ocular sulci are absent) in which a doubt might be 

 possible. 



The form of the prothorax is very different in different species 

 and appears to be quite constant, so that I have been able to use 

 it with great confidence in tabulating the distinctions of the 

 species, and a similar satisfactory result is attained by noting tiie 



