PREDATION AND EFFICIENCY IN LABORATORY POPULATIONS 227 



10 -20 -30 -40 -50 -60 -70 -80 '90 hOO 



Fig. I.— The relation between residual population size {Pp) per unit food and the intensity of 

 predation (F) in D. pulex when young animals are selectively taken as yield. 



ANIMALS OF YIELD FROM YOUNG REMOVAL 



Food Level 



X I 



« z 



Fig. 2.— The relation between yield per unit food per four days and F, when young animals are 

 selectively taken as yield (D. pulex). 



i6 



