w ws 



FIG. 217. Diagrammatic sections through the imaginal disc of a wing in various stages of 

 development, showing how the wings develop in various groups of insects. (After Tower.) 



A, wing'development in Orthoptera, Odonata (Paraneuroptera), Ephemeroptera, and many families 

 of Colooptera (cf. Cerambycidae and Buprestidae). B, wing development in Lepidoptera and in 

 Chrysomelidae (including the genera I>niiiii-!n, /'nn^'/iom, and Galerucclla amongst Coleoptera). C, wing 

 development amongst the higher Diptera (Muscidae). nd, cuticle; if, trachea; ic, rudiment of wing ; 

 w.s, wing-.s;ic. 



272 



