1408 THE BUTTERFLIES OF KEW ENGLAND. 



the thread at the tail end ; the forks wliicli are 8.5 inin. Ions: seem to be 

 as thick as the stem — pcriiaps because k'ss tightly woven — are attached 

 to the sides of the cocoon a little below the middle, and are 14 mm. apart, 

 thus diifering considerably from the cocoons formed of living leaves ; 

 aj)parently there is no spreading of the threads at their attachments ; the 

 silk of which they are formed seems to be wliiter than that of the walls of 

 the cocoon, and is in no way imbedded in the integument of the chrysalis. 

 The several changes in the external form and character of a butterfly in 

 passing from the larval to the pupal state have nowhere been so carefully 

 stated as by Agassiz in his description of this insect in a paper not often 

 quoted, so that I transfer his remarks on the subject almost bodily : — 



The first marked modiflcation from its former condition consists in a general short- 

 ening of the body. The whole larva contracts for about one-third of its length, and 

 thus assumes permanently a position whicli it shows sometimes when at rest. But 

 even after it has thus become quiet, it will, when disturbed, again move about in 

 search of a more protected shelter. 



If left undisturbed, the body is seen to swell, especially in its anterior part, which 

 seems to be in a state of chronic inflammation, as it were, having the appearance of 

 an oederaatous swelling, distended by a considerable accumulation of lymph. 



The thoracic region and the head are at this time the chief seats of the formative 

 process, and of a more active process of nourishment; the other parts seeming rather 

 to wither, the skin to shrivel, and the prolegs to dry up. Indeed, before long, the 

 skin of the larva is sufficiently loose to be separated without much difficulty from the 

 pupa formiug underneath; and by watching carefully the moment when the skin splits 

 upon the back in the process of being naturally removed, the whole process may, with 

 some assistance, be accelerated, and the skin turned away before the chrysalis is en- 

 tirely formed. At this moment the young animal presents characters so ditlerent from 

 the perfect pupa, that, unless the whole process has been carefully watched, no one 

 would suppose that the forms it then exhibits are really the nest transformation of 

 the larva towards its change into a chrysalis. 



Indeed the chrysalis, when perfect, presents a hard case, upon which, with some 

 attention, we may distinguish the outlines of the abdominal joints and the thorax; 

 upon the sides of this, and below it, an outline of the future wings may be recog- 

 nized, as well as superficial indications of the legs underneath, bent backwards be- 

 tween the wing covers ; there is likewise a tubular flattened case, representing the 

 antennae; and upon the middle Hue, a similar one answering to the proboscis. All 

 these parts are soldered together, and upon the skin itself, so closely as to be entirely 

 immovable, and to appear rather as a protecting envelope of the organs, the form 

 of which they foreshadow, than as these organs themselves. Nevertheless, if we 

 carefully watch the process of the last moulting, or, rather, if we are successful in re- 

 moving gently the larva-skin before the pupa is hardened, we see that all the above men- 

 tioned organs exist in reality, wholly independent and entirely free from each other, 

 though still imperfectly developed, since the legs are mere cylindrical tubes without 

 regular articulations ; since the antennae present a similar tubular appearance, some- 

 what swollen towards the end, but without joints; since the maxillae project as two 

 independent tubes, also very much like another pair of legs ; and since the wings 

 appear as four distinct, swollen, but somewhat flattened vesicles, identical in ap- 

 pearance with the lateral respiratory vesicles of Aunellides, sufficiently large, how- 

 ever, to remind us of the wings as they appear when the perfect insect has come out 

 from the chrysalis. We have, therefore, an apparently complete butterfly, somewhat 

 imperfect in its characters, coming out from the larva with all its parts independent, 

 prior to the period when these parts are pressed upon the sides of the animal, and 

 soldered with its walls. 



