Pupal suspension of Thais. 217 



2nd abdominal segment seems small and contracted, the 

 abdominal segments behind and the thoracic in front 

 seeming relatively swollen. 



The completion of the process, when the spinning is 

 finished, is really very different from that in Papilio. In 

 Papilio the front of the head is put forward under the loop 

 and it is slipped back into its place by a movement very 

 similar to that by which a thread is added to the girth. 

 In rapse, at the end of fixing the last thread at the side, 

 the head is merely drawn forward from under the loop. 



The references to the spinning of the loop in Pieridse 

 that I have met with, give the idea that it is spun from 

 the outside across the abdominal segments, the spinneret 

 being carried to and fro across the surface of the 

 segment — a feat that a moment's reflection on the details 

 of such a process will show to be impossible. It is made 

 across the 2nd abdominal segment, but the larva is so 

 bent back that the loop passes at the same time round 

 its neck and the spinning is from the inner- or under-side. 



When I say that the spinning from the outside is 

 impossible, it is perhaps going too far, for there is no 

 necessary limit to the amount of bending a larva may do, 

 but when one sees the amount of strain on the full-fed 

 larva of rapse to get the head as far back as it does, it is 

 seen that whatever it might be for some hypothetical larva, 

 it would be impossible for rap/e to bend further back till 

 the spinneret touches the abdominal dorsum. Or if we 

 take the actual position when the larva is fastening one 

 end of the loop, if it thence carried the spinneret up the 

 side of the segment towards its dorsum, the combination 

 of lateral bending and longitudinal twist would stop the 

 process before the spinneret reached the dorsum, much less 

 reached the other side. 



