Three or four specimens of each species are generally sufficient, except where variations in colouring are to be exhibited. Wherever differences exist in the form or markings of the sexes, both should appear; and one specimen of each species should be pinned so as to exhibit the under side. Finally, each drawer or box should have a neat label _outside_ giving the name or names of the divisions of insects that are represented within. This will enable you to find anything you may require without the necessity of opening drawer after drawer or box after box. PART III BRITISH BUTTERFLIES We have now treated in detail of the changes through which butterflies and moths have to pass, and have studied the methods by which we may obtain and preserve the insects in their different stages. I shall now give such a brief description of individual species as will enable the reader to recognise them readily. We will begin with the butterflies. CHAPTER XII _THE SWALLOW-TAIL AND THE 'WHITES'_ Family--PAPILIONIDAE _The Swallow-tail_ (_Papilio Machaon_) Our first family (_Papilionidae_) contains only one British species--the beautiful Swallow-tail (_Papilio Machaon_), distinguished at once from all other British butterflies by its superior size and the 'tails' projecting from the hind margin of the hind wings. This beautiful insect is figured on Plate I, where its bold black markings on a yellow ground are so conspicuous as to render a written description superfluous. Attention may be called, however, to the yellow scales that dot the dark bands and blotches, making them look as if they had been powdered; also to the blue clouds that relieve the black bands of the hind wings, and the round reddish orange spot at the anal angle of each of the same wings. It appears that this butterfly was once widely distributed throughout England, having been recorded as common in various counties, and has also been taken in Scotland and Ireland; but it is now almost exclusively confined to the fens of Cambridgeshire, Huntingdonshire, and Norfolk. Occasionally we hear of the capture of single specimens quite outside these localities, sometimes even in most unlikely spots, where its food plant does not abound. But we know that _Machaon_ is a general favourite with entomologists, and that it is sent in the pupal state, by post, to all parts of the kingdom; so that the occasional capture of the insect far beyond the borders of its haunts is probably the outcome of an escape from prison, or of the tender-heartedness of some lover of nature who could not bear to see such a beautiful creature deprived of its short but joyous, sunny flight.