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CHAPTER VUL 



General considerations and synopsis of the results. 



In the preceding- pages I have tried to Lay down a general 

 foundation for the arniature of caterpillars. 



In consequence of the shifting of the stigmata over mesothorax 

 and metathorax and the development of the wings on theni, I 

 take it for granted, that these segments are to be considered as 

 being secondarily modified. 



On account of the anatomical differences with the abdonien, 

 this result might a priori be expected, and the chaetotaxy on 

 these segments provides proofs that the setal pattern also has 

 undergone secondary modifications. The prothorax too has taken 

 part in these changes by obtaining the stigma which originally 

 was placed on the mesothorax. Hence it is not desirable to start 

 from these segments in reconstructing the primitive pattern, as 

 Tsou and Pracker have done (Chapters III and V). 



The anal segments too differ in structure and even vary in 

 number. This probably happens in connection with a process of 

 reduction which in some species has farther advanced than in 

 others (Chapter lY). 



Among the remaining eight or nine abdominal segments a few 

 occur hearing legs and others without them. On account of embryo- 

 logical facts as well as of the presence of the setae pedales, I 

 think it allowable to cousider the segments with legs as the 

 more primitive ones (Chapter IV). 



From the literature, Chapter II, it appears that all the different 

 investigators of the setal pattern have introduced a nomenclature 

 of their own, in which many made use of numbers. As some of 

 them indicated totally different setae by the same number and 

 as the same setae are indicated by different investigators by widely 

 diflPerent numbers, a great confusion has arisen, as is best illus- 

 trated by Plate X, fig. 1—21. 



I have therefore been led to use a nomenclature which agrees with 

 that of Weismann, W. Muller, Scudder and J. F. van Bemmelen. 



