422 Mr. F. Merrifield aucl Mr. E. B. Poulton on 



extinction due to the attacks of a single species of parasite 

 is still immense, only about f- of the whole surviving it. 



G^.— EXPERIMENTS UPON THE PUP^E OF 



Pieris ra'pse. 



1. Experiments upon the Winter Pupje of 



Pkris rapie. (F. M.) 



The next experiments tried were on this species and 



are detailed in the following section. I was late for this 



species and did not experiment with more than 50 or 60 



larvse, from which I obtained the single row of about 



40 pupse which are now shown in the Exhibition Case. 



Here I call attention to the contrast between those in 



the black surroundings on the one hand and those in 



the green paper, yellow, or orange surroundings on the 



other, the green in this species seeming more effective than 



it proved with the other species and the yellow less so. 



2. Results of the above Experiments. (E. B, P.) 

 The colour variations of the pupa3 of P. rajyx, have been 

 already described and figured (Phil. Trans. 1887, 1, c. pp. 

 410, 411, Plate 26, figs. 31—41), and it is here only 

 necessary to state that the standard classification begins 

 with the darkest pupse (1), ranging through the less dark 

 (2) and still lighter (3) to the pale (4) and the green (5). 



Mr. Merrifield's pupse were compared on March 20, 

 1899 : the results are given below without much detail, 



