18 BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



Table VII. — The monthly emergence, of moths from resting larvse for 1918 and 1919. 



Months. 



Number of 



moths 

 emerged. 



Per cent of 

 total emer- 

 gence. 



Number of 

 moths 

 emerged. 



Per cent of 

 total emer- 

 gence dur- 

 ing period, 

 covered. 



March 



April 



May 



June 



July 



August 



September . 



October 



November. 



3sl 

 236 

 525 

 355 

 105 

 16 



23.5 

 14.6 

 32.5 

 21.9 

 6.5 

 1.0 



1. 



125 



851 



1,811 



2,302 



708 



84 



40 



8 



0) 



2.1 



14.3 



30.6 



38.8 



12.0 



1.4 



.7 



.1 



Total. 



5,930 



100.0 



1 No complete record. 



Moths emerging in 1918 were from larvse collected in seed in 

 February, 1918; those emerging in 1919 were from larvse collected 

 in bolls dining November, 1918. Complete records are not available 

 for December, 1918, or January, February, and March, 1919, due 

 to absence from the laboratory. The percentages of moths emerging 

 each month are based on the total number of moths which emerged 

 and not upon the total number of larvse. Of the larvse collected in 

 November, 1918, 4.4 per cent were still alive and had not pupated 

 on November 20, 1919, when the records were discontinued. 



A study of Table VII shows that emergence took place much earlier 

 in 1918 than in 1919. During March, 1918, 23.5 per cent of the 

 moths emerged and the maximum of 32.5 per cent was reached in 

 May, while in 1919 only 2.1 per cent emerged in April and the maxi- 

 mum of 38.8 per cent was not reached till July. This seasonal 

 variation depends largely upon the temperature and humidity. 

 The winter of 1917-18 was unusually mild and there was an excep- 

 tionally hot period during the first week of March which hastened 

 pupation. It was also found that dampening the seed or lint hast- 

 ened emergence and a rain followed by warm weather in March 

 or April would no doubt cause large numbers to emerge. As a rule, 

 moths emerging before the first of May would find no suitable places 

 for oviposition and would not be a factor in starting the infestation 

 in the following crop. 



ISSUANCE OF MOTH. 



The issuance of the moth from the pupal skin requires a very 

 short time. The pupal skin breaks or splits along the dorsal side 

 and the moth works its way out and crawls upon some object in the 

 open so that the wings may develop normally. As soon as the 

 wings have extended to their full length they are raised and held 

 in a vertical position from 5 to 15 minutes to become perfectly 



