20 



1912 that J. F. VAN Bemmelen succeeded in proving this sug- 

 gestion. This writer found that the pattern of the caterpillars of 

 Pieris brassicae might be retraced in the design of the pupae. 

 He then could recognize the same pattern on pupae of several 

 other Pieridae and also of Papilionidae and Nymphalidae and 

 even succeeded in discovering it on the bodies of the imagines. 



In a following chapter (VII) containing the discussion of the 

 pupal pattern, I shall return to this important question. 



It is perhaps due to the influence of Weismann and Eimer, 

 who considered the linear-pattern as the original one, that in- 

 sufficient attention is paid to theories which regard the spotted 

 pattern as the most primitive. 



It is certain that Schroder (1894) in his study of the Geome- 

 tridae has been too much influenced by this preconceived idea. 

 This investigator has paid still less attention than Weismann to 

 the setae bearing tubercles and consequently has quite overlooked 

 the pigment accumulation at the base of the setae. For the dis- 

 cussion of the origin of the linear pattern and the primitive cha- 

 racter of the spotted pattern I refer to chapter IX. 



J. C. II. DE Meyere in his recent paper (1916) arrives at con- 

 clusions which are in general the same as mine. In chapter VI 

 and VII I shall return to his paper. 



CHAPTER III. 



On the structure of the thoracic segments. 



In several respects the construction of the thorax differs from 

 that of the abdomen, a difference which very early attracted the 

 attention of entomologists. Before discussing my nomenclature, I 

 prefer to investigate, which segments are the most primitive 

 ones, in other respects than the covering with setae. There are 

 reasons for supposing that segments of primitive construction in 

 other respects, will also display this original character in 

 their setal pattern. I cannot avoid mentioning many facts which 



