CROWDING AND INCREASED DEATH-RATE 



139 



in flour cultures containing only male beetles, the percentage of 

 eggs eaten varied directly with the population of adults per gram of 

 flour. 



Chapman's experience with Triholium can be shown in a number 

 of ways; perhaps as significant as any is the result of carrying to 

 equilibrium a series of beetle environments of different sizes, of 

 4-128 grams of whole-wheat flour, seeded with i, 2, 4, 8, 16, and 32 

 pairs of beetles each, making one pair of introduced beetles per 4 

 grams of flour. This experiment may be followed in Table III, which 



TABLE III 



gives the total number of the beetles present per gram of flour at 

 different times in the history of the cultures, regardl-ess of the de- 

 velopmental stage of the beetles. 



In all the conditions tested by Chapman, the mean number of in- 

 dividuals per gram of flour after equilibrium was established was 

 43.97, with a standard deviation of 4.27, and a probable error of 2.88. 

 Chapman found, as will be shown in detail later (chap, x), that the 

 time taken to reach this equilibrium differed with the initial seeding 

 per gram of available flour, while the equilibrium population re- 

 mained constant per gram of flour; and that, with the same initial 

 seeding throughout, the equilibrium population per gram of flour re- 

 mained constant but the time taken to reach equilibrium varied 

 directly with the quantity of flour available. This equilibrium is 

 primarily a food relation, or a food and space relation, since the 



