African Species of the Genus Acraca. 19 



from the actual specimen. Of some sixty forms repre- 

 sented, vei-y few have been previously figured. The 

 synonymy tables do not profess to give every known 

 reference, though it is hoped that none of geographical or 

 synonymic importance has been omitted. In this and other 

 respects I have not hesitated to make use of Professor 

 Aurivillius' catalogue, the constant employment of which 

 has served to increase, if possible, my intense admiration 

 for the almost incredible labour of which that work is the 

 record. The key to the species has proved by no means 

 the least difficult portion of my task. I doubt whether 

 any approach to perfection could be attained in a key to 

 so variable a genus. A key, to be quite satisfactory, pre- 

 supposes a certain stability of colour and pattern which is 

 sadly lacking in the genus Acraca; nevertheless I trust it 

 will be found of some as.sistance as a mere mechanical aid 

 to identification. An attempt has been made to arrange 

 the species in groups, and though some of these appear to 

 be fairly natural, others are much less convincing, whilst 

 in certain cases a "group" has but one representative. 

 Our knowledge of the true affinities of the species is at 

 present very elementary, and but little importance can be 

 attached to this feature of the arrangement. 



In the preparation of such a paper as the present we 

 can but make the best use in our power of the material 

 at our disposal. It must be borne in mind that our largest 

 collections contain but a small number of samples, the 

 ratio of which to the bulk occurring in nature is almost 

 infinitely small. Many of our conclusions are based on 

 the assumption that this ratio, though small, is correct. I 

 have spared no pains to follow up whatever line of 

 research the work has suggested. If the result is to 

 increase, even slightly, our knowledge of a singularly inter- 

 esting and difficult group of insects, I shall be amply repaid. 



KEY TO THE AFRICAN SPECIES OF ACBAEA. 



[The portions jirinted in italics with names of species in reman letters 

 refer to female characteristics. The numbers after the species' names refer 

 to the pages on which the descriptions will be found.] 



The two following species can be at once recognised by their 

 peculiar characteristics. 



H.-w. underside dull metallic gold with a subraarginal row of 

 crimson spots ...... . mirifica (208) 



H.-w. underside ochre-yellow with a cential band of grey 



C 2 



