DEVELOPMENT 



57 



doptera), "grub" (Coleoptera), and "maggot" (Diptera), 

 while the pupa of a moth or butterfly (especially the latter) 

 is called a " chrysalis." 



Heterometabola. In a grasshopper, as contrasted with a 

 butterfly, the imago, or adult, is essentially like the young at 

 birth, except in having wings and mature reproductive organs, 

 and the insect is active throughout life; hence the metamor- 

 phosis is termed direct, or incomplete. This type of trans- 



FIG. 204. 



A C 



Phormia regina. A, larva; B, puparium; C, imago, x 5. 



formation, without a true pupal period, is characteristic of 

 the more generalized of the metamorphic insects, namely, 

 Orthoptera, Platyptera, Plecoptera, Ephemerida (Fig. 19), 

 Odonata (Fig. 20), Thysanoptera and Hemiptera (Fig. 205). 

 These orders constitute the group Heterometabola. Within 

 the limits of the group, however, various degrees of meta- 

 morphosis occur ; thus 'Plecoptera, Ephemerida and Odonata 

 undergo considerable change of form; a resting, or quiescent, 

 period may precede the imaginal stage, as in Cicada (Fig. 



