134 ANIMAL AGGREGATIONS 



produced 2,117 adult offspring. The 80 cc. of banana-agar food with 

 an exposed surface of 23.76 sq. cm. per bottle must therefore have 

 been capable of supporting this number of larvae in the time avail- 

 able. The bottles with i, 2, and 3 original mated pairs produced, re- 

 spectively, 1,348, 1,124, and 1,877 total imagoes in 16 days. The food 

 available would have allowed at least 2,117 larvae to pupate and 

 produce adults. 



The exposed area, as well as the amount of food present, has been 

 shown to have a distinct effect upon the numbers of Drosophila pro- 

 duced. Harnly (1929) varied the area of standard food with the 



Fig. 8. — Showing the relation between productivity and the area of food with 

 Drosophila. The vertical column of figures gives density; figures on the graph show the 

 area of food surface in square centimeters. The corresponding total volume capacities of 

 the containers are: , 1181, 2365, 473, and 250. (Data and figure from Harnly.) 



depth kept constant at 25 mm. The live areas tried were those fur- 

 nished by culturing the fhes in vials, 4-ounce bottles, half-pint, and 

 pint milk bottles, and in 250 cc. Erlenmeyer flasks. These different 

 culture-containers gave food surface areas of 4.4, 11, 24, 40, and 52 

 sq. cm., respectively. Summarized results are given in Figure 8, 

 which shows graphically the effect of surface food area upon the total 

 yield from a single pair mating for a period of 10 days. The largest 

 yield under these conditions was given by a surface area of 40 sq. 

 cm.; 52 sq. cm. had about the same productivity as 24 sq. cm. The 

 viability was greatest in the flies reared with the largest amount of 

 space. 



