11 



comparatively few sticks left standing at the end of October. 

 Mr. Shepherd says, with regard to Sharqiya, " Our intensive campaign 

 was October 1916 to January 1917. The sticks that year were 

 probably kept standing well into December because we were trying 

 to clean standing sticks. In 1917 there was comparatively little 

 work done and the cutting of the sticks was probably carried out 

 much the same as in 1916. In 1918 there was a distinct attempt 

 made, at least in my provinces, to have them out early and the 

 percentage of standing sticks was by the beginning of December 

 equal to what it had been in the middle of December in the two previous 

 years. In 1919 it was advanced a fortnight earlier still, and in addition 

 very large quantities of sticks were off the ground by the middle of 

 October." Thus in the past three yeara the average date of pulling 

 in these two provinces has been advanced by at least a month. 



Reference to Table V should convince one that this change is 

 capable of making a very appreciable difference to the boll worm 

 attack. Not only does earliness have a direct effect, however, in 

 reducing the number of long-cycle worms, but it leads to a further 

 reduction of this number in two indirect ways, namely by giving the 

 parasites a longer period in which to attack the worms and by causing 

 a larger quantity of sticks to be burnt before the moths begin to emerge 

 from them. 



The chief parasite of the worms in the bolls is the ichneumon fly, 

 Pimpla roborator F. This insect, though it kills annually immense 

 numbers of boll worms, is restricted in its good work, firstly by the 

 fact that it can only get at the worms after the bolls have opened, 

 and secondly by the fact that it ceases to breed in January. Pulling 

 up the cotton sticks causes the green bolls on them to dry and open. 

 A change in the date of pulling from December 1 to November 1 thus 

 approximately doubles the period during which the worms in these 

 bolls are exposed to the attacks of Pimpla. 



The view that it is the earlier pulling of the sticks which has 

 caused the reduction in the pink boll worm attack is also strongly 

 supported by the recent history of the common boll worm in Egypt. 

 The life-history of this insect closely resembles that of the pink boll 

 worm except, that, instead of having a long-cycle generation which 

 hibernates right through the winter and spring, it has a continuous 

 succession of short-cycle generations throughout the year. Con- 

 sequently a long " close season " when no food-plants are available, 

 is much more effective against it than against the pink boll worm. 



Previous to 1912, in parts of the country, cotton was left standing 

 right through the winter, being treated as a two-year crop. In 

 1912 this was prohibited and a date was fixed by which all cotton 

 sticks had to be pulled or cut. From 1912 onwards, increasing areas 



