INTRODUCTION. 



being pei'sonally unacquainted with the country, and from the fact 

 that^it has been very Httle worked except in the neighbourhood of a 

 few centres. 



The whole subject has been as much condensed as possible, and, to 

 save space, abbreviations (lists of which are given) are very freely used. 

 With the same view, descriptions are reduced to a minimum ; the pre- 

 vailuig colours of each tribe or genus are given, and often a dis- 

 tinguishing character of the latter; then, under each species, the 

 synonyms," size, foodplant of the larva when known, and the super- 

 ficial difference between $ and $ are noted, and one or more 

 characteristics — as few as possible — given, by which each may be 

 distinguished from its neighbours. This has been by far the most 

 exacting portion of the work ; in every difficult case many specimens 

 have been examined, and, in no instance, have the distinctions been 

 drawn by reference to books or plates alone, without examination of 

 the actual insects themselves. It must be farther understood that the 

 characteristics given are often not those which scientifically diffe- 

 rentiate one genus, or even one species, from another (these being 

 often more prominent in some earlier stage), but those which are 

 easiest of recognition, and consequently the most superficial. In the 

 same way, secondary sexual distinctions have always been chosen by 

 preference, and the androconial pockets are generally referred to by 

 their appearance, aj., "a thickening of the nervures," "a black 

 line," itc, rather than Ijy their actual structure or function. The 

 stage at which hybernation takes place is given either under the tribe, 

 genus, or species. Localities are next mentioned, with dates and 

 authorities, and 1 have by preference given the most modern instances 

 that I can find, and have as far as possible taken, when there was any 

 choice, those which have not been previously published, or which were 

 scattered through the pages of magazines ; the year has been added 

 whenever possible, as times of emergence vary greatly with the 

 season ; the year 1899, for instance, was abnormally forward ; 1898, 

 and in the mountains 1902, unusually late. Lastly, special attention 

 has been paid to variation, and under the head of "Directions of 

 Variation " a good deal of information is often implied concerning the 

 type, which has enabled me to dispense with a considerable amount 

 of direct description ; when no localities are added after the various 

 forms mentioned it is to be understood that they occur with the type. 

 Variation in size is only mentioned specially when it is pronounced, 

 as all collectors must be aware that all species differ somewhat in this 

 respect ; the size given in millimeters after the name of each species 

 is an average ; this small but important item of information has 

 involved a great deal of actual measurement, the sizes given in Favre's 

 " Lepidopteres du Valais," which I had intended using as a basis, 

 being generally, though by no means always, the largest to which each 

 species attains, unless in abnormal cases. 



With regard to Classification and Nomenclature I hold strong 

 views, which would take far too much space to state here, though I 

 fear that certain inklings of them have forced their way out occa- 

 sionally in notes ; but there are two things which to me are anathema, 

 to which I must shortly refer. The ffrst of these is the breaking up 

 of large genera into "genera of convenience." 1 feel most strongly 

 that the division into genera ought, strictly speaking, to correspond 



