168 A NATURALIST IN BORNEO 



of the first two thoracic segments, and the " shoulders " 

 of the future wing-covers, are beset with little spinous 

 processes ; two such processes are also situated at the 

 posterior angles of each abdominal segment, and the 

 apex of the abdomen itself is furnished with a pair of 

 slender processes, each terminating in a grapnel-like 

 head. This complicated armature serves a particular 

 purpose, that of securing over the back of the pupa 

 the dorsal part of the last larval skin. When the final 

 moult takes place the pupa is attached by its ventral 

 surface to some tree-trunk. The ventral part of the 

 last larval skin is lost, but the dorsal part is fixed over 

 the back of the pupa, for the terminal grapnels and 

 the tiny spines hold it quite securely fore and aft. 

 Without a close examination it is not possible to dis- 

 tinguish a pupa from a larva owing to this overlying 

 blanket of larval skin. The object of the retention of 

 the larval skin is not far to seek. A pupa is a helpless 

 object unable to escape or resist its enemies ; the 

 nauseous properties of the adult larval Lycostomus, which 

 are their protection against foes and are well adver- 

 tised by bright colours, are undoubtedly present in 

 the pupa, but not coupled with a conspicuous adver- 

 tisement. There is no doubt that nature could evolve 

 a pupa with a conspicuous warning colouring, but she 

 has other methods of arriving at the same result 

 and here we have an example. The pupa, by retaining 

 the last larval skin, borrows, so to speak, the warning 

 advertisement of the larva, and thus acquires immunity 

 from the attacks of enemies familiarized by experience 

 with the larval colouring. 



The larva of Calochromns dispar is very different in 

 outward appearance from that of the Lycostomus. The 



