chap, xiv.] LARVAL STAGES OF INSECTS. 



533 



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- 

 aginal 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- 

 iiial discs, which 

 are formed of 

 minute cells, 

 and enclosed in 

 a structureless 



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

 T-orvIrlUT 4- "Ur> Salanus ; 2, Larva of Chtliamalus stellatv* ; 3, Older 

 rapidly , \ Larva of Lepas avftralis. (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 ; tlie cephalic 



