Adjustment, of colour in various ^wp^, etc. 421 



otherwise similarly fixed, one was a greenish (1 y) and 

 one, emerging, was probably a (1 y) or (2). 



Two pupiE were fixed to the parti-coloured surtace ot 

 the roof. Of these one diagonally crossed two black 

 squares in a manner very similar to that of the first 

 described of the two dead pupas in the first box, which 

 could not be classified with certainty. The direction of 

 the body was oblique with the head away from the light. 

 ]t had emerged, but had clearly been a (2) or (3). The 

 second was fixed in another bay, near to and parallel with 

 the glass. The posterior f of the body crossed a black 

 square, the anterior | was on the next orange one. _ It had 

 emerged but had evidently been a (1 ^) with quite dark 

 pigmentation. There was no trace of less pigmentation in 

 the anterior third of its body. • i • 



These results entirely confirm those obtained m the 



first box. 1 • 1 • 1 4. u 



Although further experiments of this kind are to be 

 desired, especially upon so sensitive a species as P. napi, 

 it may be regarded as certain that the conclusions derived 

 from the earlier experiments with conflicting colours are 

 sound, and that not parti-coloured pupai but uniform 

 intermediate ones are obtained in this way. 



i^._NOTES ON THE STRUGGLE FOR EXISTENCE 

 IN THE LARViE OF Fieris hxissicai. (E. B. P.) 



I have previously noted the numbers of this species 

 which perish from the attacks of parasites in a year m 

 which the larva? are specially abundant. It seemed ot 

 interest to obtain further records, and I accordingly asked 

 Mr. Holland and Mr. Hamm to keep notes of the number 

 of iarva? attacked by ichneumons and the numbers dying 

 apparently from other causes, which they removed from 

 the cases containing the mixed larvffi from St. Helens and 

 Oxford (see p. 409). The results are recorded m the table 

 on the following page. 



In the breeding-cases from which these larvae were 

 removed only 121 pupa3 were taken, including the dead 

 ones ; so that the extinction is on a vast scale. Even if 

 It be conceded that the larvae dying without the appear- 

 ance of parasites, and the dead pupse, were entirely due to 

 the conditions of experiment (such as the possible intro- 

 duction and spread of some form of bacterial disease), the 



