THE SILKWORM ITS FORM AND LIFE HISTORY. 33 



lengths, according to the part of the wing from which the scale is 

 taken. The single pointed end is that by which the scale is 

 attached to the wing. In the membrane there are a series of 

 tiny pits, which can be easily seen with a microscope when the 

 scales are removed ; into these the pointed ends of the scales are 

 inserted, and there is no other place of attachment than this. The 

 scales are laid so close together that they lap over one another 

 like the slates on the roof of a house. The wing may be denuded 

 of its scaly covering, and its transparent nature thus clearly shown 

 by careful brushing with a camel's hair brush, but there is con- 

 siderable danger of tearing the tissue of the wing in the process. 

 By chemical operations, the wings may be bleached, and rendered 

 transparent, and then the arrangement of the. nervures becomes 

 manifest. To do this, the wings are soaked for a time in strong 

 alcohol, so as to absorb all grease. Then they are laid in a 

 solution of bleaching-powder, or chloride of lime till the colour 

 disappears ; they must not be left too long in this solution, or 

 they will become damaged. Next they are transferred to a weak 

 solution of hydrochloric acid for a short time, and then from that 

 to pure water. After being well washed, they may be dried, when 

 they will be seen to be transparent, with the bleached scales still 

 in position. At the outer edge of both wings the covering of 

 scales terminates in a kind of fringe, made of more elongated 

 scales. The hairs which cover the body pass by insensible 

 gradations into the scales which cover the wings. 



At the upper corner of the hind wing, close to the body, there 

 is a thorn-like spine, which is a characteristic feature of moths, 

 but is not found in butterflies. In those species that fly, it serve? 

 to hook together the fore and hind wings, which thus present a 

 more unbroken surface to the air in the down stroke of the wing. 

 In the present insect, however, it has now no such use, as the silk- 

 worm moth has altogether lost the po\ver of flight, and occupies 

 itself merely with aimless flutterings, in which the wings are 

 kept separate. 



Such is the creature which, by means of a series of most 

 romantic changes, the wonderful processes of nature have 

 elaborated out of the tiny slate-coloured egg with which the cycle 

 commenced. By far the greater part of its existence has already 

 been passed through, and it has now not much more than a week 

 to live. The great business of perpetuating its race is all that now 

 lies before it ; when this is accomplished, its mission will have 

 been fulfilled, and it will perish. As soon, therefore, as the moths 

 have dried their wings after exclusion from the chrysalis, the males 

 seek their partners, and the pairing takes place without delay. 



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