340 



PHYL UM A R THR OPODA. 



their superficial resemblance to those which are nauseous ; a lew strike 

 " terrifying attitudes," while others are like pieces of plants. 



But for our purpose it is perhaps more important to recall the 

 differences between the respiration of some larva? and that of the adult, 

 between the apneustic larva of the dragon-fly and the holopneustic 

 winged adult. Likewise of great importance, and supplying a basis 

 for classification, are the changes in connection with the mouth organs 

 (see p. 329). 



Internal metamorphosis. In Insects with no marked 

 metamorphosis, or with merely an incomplete one, the 



FlG. 168. Development of blow-fly (Calliphora erythrocephala}. 

 After Thompson Lowne. 



The lower figure (A) shows the adult larva (maggot). Note, as 

 compared with the caterpillar, the absence of appendages, 

 except those about the mouth; k., the large hooks connected 

 with the maxillae ; /./., pro-legs. 



The upper figure (B) shows the pronymph removed from the pupa- 

 case. In the abdominal region the imaginal discs are shown ; 

 /. , rudiments of legs ; 71'., of wings. 



organs of the larvae develop gradually into those of the 

 adult. But in Insects with complete metamorphosis there 

 is a marvellous internal reconstruction during the later 

 larval, and especially during the quiescent pupal stage. 

 Most of the larval organs are disrupted and partially 

 absorbed by amoeboid cells, their debris being used in 

 building new structures. Parts of larval organs which 

 have not been highly specialised form the foundations of 

 new adult structures. Of special importance are certain 

 ingrowths of the larval skin (the epi- or hypo- dermis) which 



