THE STATE ENTOMOLOGIST, 127 



its enemies. This cocoon is said by Fitch to so closely resemble that of Luna, 

 that the two cannot be distinguished from each other, and Harris speaks of 

 their great similarity : but with us they are very easily distinguished. That 

 of Polyphemus is not only more dense, but its fibres are intermixed and 

 cemented with a gummy substance which Avhen dry gives the cocoon a 

 hard chalky appearance. This hardness renders the exit of the moth un- 

 usually tedious and difficult, and the process has been so .well described by 

 Mr. Trouvelot, that though I have watched it myself, 1 repeat his words : 



" But the moth must have some means of exit from the cocoon. In 

 factit is provided with two glands opening into the mouth, which secrete 

 during the last few days of the pupa state, a fluid which is a dissolvent for 

 the o-um so firmly uniting the fibres of the cocoon, This liquid is 

 composed in great part of bombycic acid. When the insect has accomplished 

 the work of transformation which is going on under the pupa skin, it man- 

 ifests a great activity, and soon the chrj^salis 

 covering (Fig. 54) bursts open longitudinally 

 upon the thorax ; the head and legs are soon 

 disengaged, and the acid fluid flows from the 

 mouth wetting the inside of the cocoon. The 

 process of exclusion from the cocoon lasts for 

 as much as half an hour. The insect seems to 

 be instinctively aware that some time is required to dissolve the gum, as it 

 does not at first make any attempt to open the fibres, but seems to 

 wait with patience this event. When the liquid has fully penetrated the 

 cocoon, the pupa contracts its body; and pressing the hinder end, which is 

 furnished with little hooks, against the inside of the cocoon, forciblj' ex- 

 tends its body ; at the same time the head pushes hard upon the fibres 

 and a little swelling is observed on the outside. These contractions and 

 extensions of the bod}' are repeated many times, and more fluid is added to 

 soften the gum, until under the efforts the cocoon swells, and finally the 

 fibres separate, and out conies the head of the moth. In an instant the legs 

 are thrust out, and then the whole bod}- appears; not a fibre has been broken, 

 they have only been separated.* 



"To observe these phenomena, I had cut open with a razor, a small por- 

 tion of a cocoon in which was a living chrj'salis nearly teady to transform. 

 The opening made was covered with a piece of mica, of the same shape as 

 the aperture, and fixed to the cocoon with mastic so as to make it solid and 

 airtight ; through the transparent mica I could see the movements of the 

 chrysalis perfectly well." 



Mr. Trouvelot also gives some very interesting facts to show the won- 

 derful vitality of the chr^'salis. He once thrust a pin through a cocoon 

 which he wished to preserve, and, as might be supposed, the pin also pierced 

 through the body of the chysalis inside. This was done in October, and 

 nine months afterwards, in June of the following year, he was surprised to 

 find a great commotion in the cabinet where the specimen was pinned, and 



* As I have already intimated (p. 74) this statement is not sutlieiently guarded. 



