40 COTTON 



crop. The most effective means of checking its 

 depredations are : (i) to treat all seed at the time of 

 ginning in such a way that the worms protected in 

 the coupled seeds may be destroyed ; (2) to remove 

 and burn all bolls found on the cotton plants after 

 the last picking ; and (3) to confine all cotton seed 

 remaining in the country after April in buildings 

 fitted with wire netting over the apertures to prevent 

 the emerging moths reaching the cotton fields. Various 

 methods of destroying larvae in seed have been 

 studied, and the following have been found effective : 

 (i) treatment with hot air at 5 to 65 C. for about 

 four minutes ; (2) fumigation with carbon disulphide, 

 hydrocyanic acid gas or sulphur dioxide ; and (3) im- 

 mersion in " cyllin " solution (o'i per cent.) for 24 

 hours just previous to sowing.* 



Cotton Worms. The American cotton worm 

 (Alabama argillacea] is a bluish-green caterpillar with 

 small black spots or black stripes on its back. It 

 devours the cotton leaves, not infrequently stripping 

 the plant bare. The moth usually lays her eggs on' 

 the under-surface of the leaf. The eggs hatch in 

 three or four days, and the young larvae or cater- 

 pillars emerge. The larval stage lasts from one to 

 four weeks, and the caterpillar is then transformed 

 into the pupa or chrysalis, which is generally en- 

 closed in a rolled leaf. After a period varying from 

 a week to a month the moth emerges. Each moth 

 lays about 500 eggs, and there are usually five or 

 six generations produced during a single season. 

 The larvae and eggs are preyed upon by numerous 

 parasitic insects. 



The principal method employed for the destruction 

 of the cotton worm is by the application of poisons 

 as already described in connection with the American 

 boll-worm. A favourite way of dusting the plants 

 with Paris green is to place a pole, carrying a sack 

 of the powder at each end, across the back of a horse 

 or mule and then ride the animal between the rows 

 of cotton. By jarring the sacks, a small quantity of 



* Of these methods, the hot-air treatment has been accepted as the 

 most practicable, and a law has been promulgated in Egypt requiring 

 all ginneries to instal approved machinery to carry it out. 



