INTRODUCTION 13 



Method of Arrangement. 



The natural order of arrangement, which is that of a much- 

 branched tree, cannot be adequately expressed by a simple 

 linear succession, such as is alone practicable in a book. It is 

 however possible to devise a linear succession which shall be 

 consistent with the natural genealogical order, if some ad- 

 ditional explanation can be given. The method here adopted 

 is as follows. 



Suppose the accompanying diagram represents a portion of 

 the genealogical tree ; then the order will begin at M and descend 

 to K, recommence at L and descend to K, and thence to G, 

 recommence at H and descend to G and |^ 

 thence to B, recommence at F and descend 

 to D, recommence at E and descend to D 

 and thence to B, recommence at C and 

 descend to B and thence to A, and so on. 

 Thus the order begins with the most recently 

 developed forms and descends gradually to 

 the earliest or most ancestral, which are the 

 last in the book. To understand the order 

 in practice, it may be assumed that each genus 

 is descended from that which immediately follows it in the 

 book, unless its actual descent is expressly stated otherwise; 

 such statement will of course require to be made before every 

 recommencement of a fresh branch. This system has been 

 adhered to throughout, and after a little use will not be found 

 unintelligible. If adopted in the arrangement of a collection in 

 the cabinet, it would be a good plan to indicate the recommence- 

 ment of a fresh branch by a special mark, such as a red bar 

 drawn above the first (or highest) species. 



In the arrangement of species within each genus the same 

 plan has been followed ; but since a more intimate study of 

 very minute points than has been here possible would be 

 required to ascertain accurately the mutual affinities of forms 

 which are often veiy closely related together, it has not been 

 thought necessary to enter into any very precise explanation 

 of their order. 



Nomenclature. 



The full name of each insect consists of two parts, the 

 generic and specific, taken togethex", e.g. Vanessa urticae ; and 

 it is a mistake to employ the specific name by itself. Frequently 

 the same species has received different names from different 



