COTTON 397 



carbon bisulphide, which kills all larvae present in half an 

 hour, if applied at the rate of i c.c. of the fluid to each 

 litre space contained in the cotton seed vat. Exposures 

 of less than half an hour are not always safe, nor are 

 quantities of less than O'l per cent, carbon bisulphide. 



Hydrocyanic acid gas also gives good results, but 

 requires longer to kill the worms. Sulphur dioxide is 

 also distinctly promising, but it has not been possible 

 for us to make a thoroughly satisfactory experimental 

 arrangement for the use of this gas on a small scale. 



(3) Treatment with Cyllin. A remedy usable only on 

 a small scale is immersion in cyllin and water. We have 

 found that steeping for twenty-four hours in solutions of 

 i : 100, i : 500 and I : 1,000 has no injurious effect whatever 

 on the seeds, and yet kills every worm in the sample. 

 The only objection to the method is that the seed must 

 be instantly planted, as the long immersion is apt to start 

 the germination. The seed will germinate, and the seed- 

 ling grows readily when watered with i per cent, cyllin. 



In an Appendix given at the end of this paper will be 

 found the figures on which all these deductions are based. 



In our opinion the pink boll worm, which has in three 

 years sprung into existence as a major cotton pest, need 

 not be feared as much as either the Egyptian cotton worm 

 or the ordinary boll worm (Earias), for, provided the 

 desired legislation is enforced and the power is given to 

 carry out the necessary operations, it ought to be possible 

 to restrict its ravages to a minimum. 



