vii] PUPAE AND THEIR MODIFICATIONS 81 



Diptera. In some cases the pupa requires to be 

 specially adapted for a peculiar mode of life; for 

 example, a special arrangement of breathing organs 

 may be necessary for life under water, and there must 

 needs be temporary pupal structures, not represented 

 in the imago. 



On the other hand, in the pupae of most Lepido- 

 ptera and of some Diptera, there is more or less 

 coalescence between the cuticle of the appendages 

 and the cuticle of the body generally, so that the 

 appendages do not stand out, but being, as it were, 

 glued down to the body, are somewhat masked (see 

 fig. 1 e and fig. 23). Consequently the obtect pupa, 

 as this type is called, does not resemble its imago as 

 fully as a free pupa does. The outline of the wings 

 for example in a butterfly's pupa can in some cases be 

 traced only with difficulty. T. A. Chapman has shown 

 (1893) that the completely obtect pupa characterises 

 the more highly developed families of Lepidoptera, 

 while in the more primitive families the pupa is 

 incompletely obtect. If the pupa of a butterfly or 

 moth be lifted and held in the hand, a bending or 

 wriggling motion of the abdomen can be observed. 

 In the incompletely obtect pupa, this motion is evi- 

 dent in a greater number of segments than in the 

 completely obtect, the number concerned varying 

 from five to two in different families. In the 

 nymphalid butterflies, the pupa is often called a 



c. i. 6 



