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ENTOMOLOGY 



2. EXTERNAL METAMORPHOSIS 



Metamorphosis. One of the most striking phenomena of 

 insect life is expressed by the term metamorphosis, which 

 means conspicuous change of form after birth. The egg of 

 a butterfly produces a larva; this eats and grows and at length 

 becomes a pupa; which, in turn, develops into an imago. 

 These stages are so different (Fig. 27) that without experi- 



FIG. 203. 



Cyllene pictus. A, larva; B, pupa; C, imago, x 3. 



ence one could not know that they pertained to the same 

 individual. 



Holometabola. The more specialized insects, namely, 

 Neuroptera, Mecoptera, Trichoptera, Lepidoptera, Coleoptera 

 (Fig. 203), Diptera (Figs. 204, 29), Siphonaptera (Fig. 30) 

 and Hymenoptera (Fig. 280), undergo this indirect, or com- 

 plete^ metamorphosis, involving profound changes of form 

 and distinguished by an inactive pupal stage. These insects 

 are grouped together as Holometabola. 



Larvae receive such popular names as " caterpillar " (Lepi- 



1 These terms, though somewhat misleading in implication, are cur- 

 rently used. 



