CHAPTER IV 



THE HIDDEN TYPE OF WING-GROWTH 



IN our second chapter we emphasized the distinction that 

 may be drawn between the open and the hidden types 

 of wing-growth in insect life-histories. We turn now to 

 consider some details of the latter type as they are exhibited 

 by various insects suitable for comparison with the butterfly, 

 its pupa, and its larva the caterpillar, which served as our 

 example of the type in that preliminary study. It will be 

 convenient to take these details in three sections and to 

 discuss, firstly : some typical modifications among insect 

 larvae ; secondly : differences in the form and behaviour among 

 pupae ; and thirdly : variety in the changes undergone by the 

 internal organs, including the inwardly-growing imaginal buds 

 of the larva. 



(a) SOME FORMS OF LARVAE 



At the close of the second chapter it was pointed out that 

 the contrast between butterfly and caterpillar, though super- 

 ficially striking, should not be exaggerated and that among 

 other insects which practise what we define as the hidden 

 type of wing-growth, a graded series illustrating various 

 degrees of divergence between imago and larva can be readily 

 demonstrated. In many insects the larva differs less from the 

 imago than the caterpillar from the butterfly ; in many again 

 it differs much more. 



The beetles afford an excellent introduction to the study 

 of this subject because among them great differences in the 

 modification of larval form may be observed. 1 They are to 

 be regarded as a well-marked order of insects whose name 



1 J. C. Schiodtc : " De Metamorphosi Eleutheratorum ". Naturhisi. 

 Tiddskrift, I-XIII. 1861-1883. 



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