CHAPTER I. 



Introduction, Material and Method. 



§ 1. Intrmluctioii. 



The well-known treatise of Weismann (1876) on the Sphingid- 

 caterpillars has given rise to many recent investigations of the 

 Lfpidoptera. It very soon became evident that many important 

 discoveries could still be made about these well-known insects, 

 although they have been observed for centuries, even if one con- 

 fines oneself to external characteristics only. The studies of 

 Weismann on the seasonal dimorphism (1876), the rediscovery 

 of Ratzeburo's observations (1840) on the external sexual charac- 

 teristics of the pupae by Jackson (1890) and Poulton (1890), 

 the studies by Poulton on the antennae and wingsheaths of the 

 nymphae, the enlargement of our knowledge of the primary colour- 

 pattern on the wings of the butterflies by J. F. van Bemmelen 

 (1890), the investigations by Spuler (1892) of the wingveins and 

 by Walter (1885) and Chapman (1893 B) of the active mandibles 

 of Micropteryx are the most striking proofs, of how many im- 

 portant and successful investigations could still be made in the 

 morphology of the Lepidoptera, in the last decades. 



W. MCller's (1886) treatise showed us the constancy in the 

 arrangement of the so-called primary hairs of the Nymphalid-cater- 

 pillars. In a supplement this writer points out, that the same 

 pattern occurs also in other families. 



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