42O COTTON 



tion, such food consisting of the shoots emanating from 

 cotton, bamiah, or tehl, which have been left in the 

 ground. Upon these the females lay isolated eggs in 

 the most protected positions possible, and the larvae 

 emerge, after a further dormant egg period, to carry 

 on a precarious existence upon the limited food supply 

 available. 



Probable Vitality of Generations. During the earliest 

 brood it is probable that only 10 per cent, of the eggs 

 laid produce moths for the next generation, but it may 

 safely be reckoned that 50 per cent, of each of the 

 subsequent ones survive. 



From experiments which have been made by Mr. 

 Willcocks, and which have been previously quoted, the 

 average number of eggs laid by a female moth in 

 December and January is determined as 140, and the time 

 occupied by a female for the complete oviposition at this 

 season varies from eight to forty-four days. On the 

 other hand, a female kept under observation by Mr. 

 Willcocks in September continued laying for five nights 

 only, but deposited 233 eggs. 



In order, therefore, to give some idea of the rate of 

 propagation of the Earias boll worm throughout the 

 year, the following calculation is considered a fair one. 



Assuming that the females in the first generation lay 

 140 eggs each and in the following generation 200 eggs, 

 an estimate of the production in the fifth generation 

 (October) from one pair of moths, the female of which 

 laid in January, can be arrived at as follows : 



i pair produces 140 eggs, of which 10 per cent. = 14 

 produce moths. 



7 pairs (14 moths) produce 200 eggs each == 1,400, of 

 which 50 per cent. = 700 produce moths. 



350 pairs (700 moths) produce 200 eggs each = 70,000, 

 of which 50 per cent. = 35,000 produce moths. 



17,500 pairs (35,000 moths) produce 200 eggs each = 

 3,500,000, of which 50 per cent. = 1,750,000 produce 

 moths. 



One female moth which laid in January would there- 

 fore be responsible for the production in October of 

 3,500,000 boll worms, of which, at a very moderate 

 estimate, 1,750,000 would survive to become mature. 



