viii PREFACE. 



therefore given, and are followed by indications of the 

 directions which variation is known, in each species, to take. 

 In order to meet the difficulty often found in readily dis- 

 criminating a species by means of a long description, a short 

 diagnosis (which it has not seemed necessary to render 

 into Latin) is given in every case ; and, where desirable, Mr. 

 Stainton's admirable method of tabulation has, in addition, 

 been used. 



39 Linden Gkove, Nunhead, 

 London, S.E. 



March 1893. 



