LEPIDOPTERA. 225 



within, its legs without, the worm arranges its thread all round its 

 body, describing ovals with its head. It approximates gradually 

 the points of attachment of the thread. As long as the cocoon 

 is not very thick one can watch it through the meshes of the web 

 applying and fixing its thread, still to a certain degree soft, in such 

 a manner as to make it adhere closely to the parts already formed. 



"We can state," says M. Robinet, "that the silkworm makes every 

 s^^ond a movement extending over about five millimetres. The 

 length of the threads being known, it follows that the worm moves 

 its head three hundred thousand times in making its cocoon. If it 

 employs seventy-two hours at its work, it is a hundred thousand 

 movements every twenty-four hours, four thousand one hundred and 

 sixty-six an hour, and sixty-nine a minute, that is to say, a little more 

 than one a second." 



About the fourth day, after having expended all its silk,* the 

 worm shut up in the cocoon becomes of a waxy white colour, and 

 swollen in the middle of its body. The abdominal legs wither away ; 

 the six fore legs approach each other and become black. The parts 

 of the mouth tend downwards ; the skin wrinkles. Very soon it is 

 detached and pushed down towards the hinder part, and the chrysalis 

 appears under the rents in the skin. It is at first white, but speedily 

 becomes of a brown red. 



The silkworm remains in general from fifteen to seventeen days 

 in the pupa state. At the moment of hatching, the moth begins by 

 breaking the skin in which it is shut up, and which is pretty thin. 

 But how can it come out of the silky prison which it has itself built ? 

 To effect this it makes use of a peculiar liquid contained in a Httle 

 ; bladder with which its head is i^rovided, and which was discovered 

 ,by M. Guerin-Me'neville. It moistens the cocoon with thishquid; 

 ■ which soaks through and penetrates the whole thickness of the silken 

 wall which confines it. The threads of silk of which it is composed 

 are moistened and disunited, but not broken. The moth opens 

 a passage for itself through the threads thus separated, and makes its 

 appearance in the light of day. Its wings are folded back on 

 themselves, and it is still quite wet, but it seeks immediately for a 

 good place in which to dry itself, and in a little time assumes its 

 final appearance (Figs. 209, 210). The female (Fig. 210) has 

 whitish wings, the antennae only slightly developed and pale, the 

 abdomen voluminous, cylindrical, and well filled. It is quiet, heavy, 

 and stationary. The male is smaller \ its wings are tinged with grey, 



* " Manuel de I'Eclucateur du Vei^ a Soie," p. 37. 



