28 BRITISH LEPIDOPTERA. 



measured, immediately on moulting, l-87in. in length, made up of 

 (1) # 63in. from anterior extremity to end of wings. (2) l-24in. to 

 posterior extremity. After two hours the relative lengths had become 

 (1) 1-lin. and (2) -78in., so that the changes represented (1) -63 : 1-1 

 and (2) 1-24 : -78. The alteration in the proportion of parts that 

 occurs within 40 minutes of the moult of P. bucephala is certainly 

 remarkable. The length of the pupa in sixteenths of an inch is, 

 immediately the moult has taken place, 17. Dividing the length into 

 three parts : (1) From anterior extremity to end of wings. (2) Thence 

 to hind margin of 6th abdominal segment. (3) Thence to anal 

 extremity, the comparative measurements at intervals of ten minutes 

 were : — 



1.— At moult . . ..7:6:4 3.— After 20 minutes 8:5:4 



2.— After 10 minutes 7$ : 5£ : 4 4.— After 30 minutes 8£ : 4£ : 4 



5. — After 40 minutes . . ..9:4:4 



This is caused partly by the growth of the wings and appendages, till 

 they reach the hind margin of abdominal segment four, and partly by 

 shrinkage of segments five and six. Chapman considers that this is 

 due to a great extent to fluid presssure from the contracting portions 

 of the insect, produced probably by muscular action, combined with 

 the ingestion of air. As bearing on this point, he further suggests 

 that the activity of the valves of the spiracles has something to do 

 with the regulation of fluid pressure in connection with the redistri- 

 bution of plasma and expansion of appendages, then so actively taking 

 place. 



Not only is the proportion of parts altered in the early stage of 

 pupal existence, but their shape is considerably modified. Thus 

 Chapman notes the newly-formed pupa of Sphinx ligustri as having 

 the segments all very marked and rounded, Avith deep incisions, the 

 terminal full and blunt, not tapering as in the adult pupa, the 5th and 

 6th abdominal segments being especially large and globular. The 

 head stands out and somewhat apart, as it does permanently in many 

 Tineid pupa?. The proboscis-case forms a square projection -1 inch 

 in length and width, but bent down somewhat already, markedly bifid, 

 and the two lateral halves easily separated. This case assumed its 

 permanent shape and length of nearly -28 inches in about an hour." 

 Edwards notes (Canadian Entomologist, ix., p. 229) that, when the larval 

 skin of Polygonia inter rogationis is first thrown off, the chrysalis hangs 

 limp and distended like a long cone, with no prominences except the 

 mesonotum. Presently, he says, the segments "shorten and become 

 broader, the ends of the wing-cases creep nearer the tail, the tubercu- 

 lated points on the abdomen swell out, the head-case pushes up, with 

 its palpi-cases, and, in the course of half-an-hour, the final and 

 characteristic shape is assumed. The change, in these respects, is 

 nothing like so striking in Polygonia as in Limenitis, where the chrysalis 

 is greatly hunched and displays a prodigious mesonotum. In this 

 case, also, the chrysalis is at first limp and shapeless, but reaches its 

 proper form in the same way, the segments contracting and the 

 processes growing and maturing as one looks at them." Osborne 

 notes that, at the moment of exclusion, the anterior horn of the chrysalis 

 of fiuchloe cardamines is a minute (ventrally), incurved process, and it 

 may almost be seen growing till in an hour or two it has attained the 

 completed size when it is equal in length to the posterior horn. 



