156 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- 
Fic. 203. 
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Nid 
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ii 
A 
Cyllene pictus. A, larva; B, pupa; C, imago. xX 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. 
‘ 
Larve receive such popular names as “ caterpillar’ (Lepi- 
*These terms, though somewhat misleading in implication, are cur- 
rently used. 
