200 



PTILOTA. 



The existence and the niimher of legs of the larva, the 

 permanent or variable form of the head, the comparative 

 structure of the organs of the mouth with those of the 

 imago, the number of the spiracles and disposition of the 

 trachese, the moultings of the skin, and the quiescent or 

 active state of the pupa, are all important considerations, 

 upon which the distribution of insects from the characters of 

 their metamorphosis may be effected. 



Hence the Lepidoptera (figs. 35, 36, and 37), are dis- 

 tinguished by the number of legs, scaly head, &c. of the 



Figs. 38, Larva — 39, Pupa coarctata — 10, Imago of Stratiomys cliatna;leou. 



caterpillar {Eruca Latreille), and the obtected, or, as 

 Latreille prefers calling it, the mummy-formed pupa {Chry- 



Figs. 41, Larva; 42, Pupa inconnilcta; 43, Imago of Chrysomela populi. 



salis Latreille). The Diptera (figs. 38, 39, and 40) arc ihs- 

 tinguished by their worm-Uke larvai {Vermilarva Latreille), 



