CHAPTER III 

 METAMORPHOSIS 



Berlese's Theory, p. 51. Types of Larv^, p. 56. 1. The Protopod 

 Type, p. 56 ; 2. The Polypod Type, p. 58 ; 3. The Oligopod Type, 

 p. 60 ; 4. The Apodous Type, p. 60. General Remarks on Insect 

 Metamorphosis, p. 61. Nymphs and Pupce, p. 63 ; Hormones and 

 Metamorphosis, p. 64. Literature, p. 70. 



The general features of insect metamorphosis are well known 

 and consequently do not require recounting. The present chapter, 

 therefore, will be confined to a discussion of the more recent 

 aspects of the subject, and the theories that have been advanced 

 to account for some of the phenomena associated therewith. For 

 many years past the compodeiform type of larva has been claimed 

 to be the most primitive form of immature insect, while departures 

 from this condition have been explained as being the result of 

 secondary and adaptive modifications. While there is considerable 

 truth in this idea, it fails as a complete explanation of insect 

 transformation, and leaves many problems unsolved. 



Berlese's Theory 



A comprehensive and largely new interpretation of insect meta- 

 morphosis was advanced by the late Antonio Berlese in 1913, and 

 was subsequently incorporated by him in his well-known treatise, 

 " Gli Insetti." His views attracted little or no attention until 

 1925, when the present writer adopted certain of Berlese's main 

 conclusions as a general theoretical explanation of the diverse 

 facts of metamorphosis. During the five years that have followed, 

 the writings of de Gryse (1926), James (1928), Eastham (1929), 

 Chrystal (1930), and others have contributed facts bearing upon 

 the theory, but the latter has not received the recognition it 

 merits. 



In the first place, Berlese's theory takes into consideration the 



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