264 



Euchloe cardamineSj Gonopteryx rhamni and Thais jMlyxeHn^ 

 I have only made Indian ink drawings, with the aid of the 

 „Zeichenapparat naeh Abbe (Zeiss. Jena)." For the composition of 

 the plates, these enlarged drawings were all reduced to the same 

 size: + 10 cm., by photographic reproduction. In consequence the 

 smaller and younger specimens are represented on a much larger 

 scale than the bigger and full-grown animals, but their actual size can 

 always be accurately ascertained by the scale given with each figure. 



These figures have the advantage that they reproduce the real 

 aspect of the animals. 



The implantation and in most cases also the length of the setae 

 lias been traced exactly from the fresli or conservated specimens. 

 Except where a homogeneous spreading of the setae occurred and 

 I had to work according to a scheme, I could always use this 

 method. This method of drawing from life with a magnifying 

 apparatus, and of reducing these enlarged figures to a certain 

 Standard length, seems to me preferable to that foliowed by Tsou 

 (1914). This writer describes a method by which the length and 

 the breath of the setae can be determined. In chapter II I shall 

 refer to his work. 



In my method, which lias also been applied in Packard's work 

 on the Bombyces (1895 — 1914), the growth in length becomes 

 so to speak eliminated, and therefore the variations of the pattern 

 becoine more distinctly visible. At the same time these figures 

 can be used to study the growth in thickness of the successive 

 segments in the different instars, as the correlations of growth 

 fully deserve to be studied further. I believe that up till now only 

 the head lias been studied in this manner. The well-known leaps 

 in the changes of the size of the head have often assisted me to 

 determine the moment of the moult, in cases where this was 

 not mentioned with the preserved material. Many investigators 

 have only turned their attention to the fullgrown caterpillars. It 

 therefore seemed to me an interesting subject to examine the 

 placing of the setae in all instars as accurately as possible. The 

 difference of the results of my investigations and of those of many 



