chap, xiv.] LARVAL STAGES OF INSECTS. 



533 



t 



even in this pupal stage, it continues to move about 

 actively ; during the pupa stage a number of changes 

 occur within the body, and organs, such as the wings, 

 which were ab- 

 sent from the 

 larva, are de- 

 veloped from 

 masses of indif- 

 ferent cells, the 

 so-called im- 

 agiiiai discs. 

 The most com- 

 plete series of 

 changes during 

 the pupal period 

 obtain in the 

 Flies; all the 

 organs of the 

 larva,except the 

 generative, un- 

 dergo degenera- 



tion, while the 

 abdomen of the 

 imago is derived 

 from that of the 

 larva ; the imag- 

 inal discs, which 

 are formed of 

 minute cells, 

 and enclosed in 

 a structureless 



capsule, grow Fig. 219. Larval form of Cirripedia. 1, Nauplius of 

 yaTMVTUr fTi/ioo Balanus ; 2, Larva of Chthamalus stellatus ; 3, Older 

 - 11 J ) u Larva of Lepas australis. (After Woodward.) 



in the lower 



portion of the thorax become united by pairs, and give 

 rise to the legs those in the upper portion become 

 converted into the wings and halteres ; the cephalic 



