﻿STUDIES OP THE PINK BOLLWOEM IN MEXICO 39 



plat and 16 in the plat that was plowed only. However, some later 

 examinations show up entirely differently. Thirteen living speci- 

 mens were found in a square yard from plat 2 on April 17, and the 

 same number in a square yard from plat 3 on May 1. It is evident 

 that further experiments should be conducted. 



In addition to the soil examination, three cages were placed on 

 each plat (except plat 5) to catch any emerging moths. Each cage 

 covered 1 square yard and had a trap arranged in the middle to 

 catch emerging moths. Paper covers were placed on the cages at 

 night, leaving only the traps exposed. It was thought that moths 

 seeking light or free air would more readil}^ enter the traps in this 

 way. The cages were examined every second or third day with the 

 following total results: 



Plat 1. 2 moths, April 15. 



2. 1 moth, April 15. 



3. moth. 



4. 1 moth, April 30. 



In August all these cages were removed and the, surface of the soil 

 under each one carefully examined for signs of any moths that might 

 have emerged and not entered the traps. Only the following were 

 found : 



Plat 1. 1 dead pupa in cocoon on surface of ground, 1 pupal case under base 

 of cage. 



2. 1 pupal case under clod of earth. 



3. 1 pupal case under clod of earth. 



4. 1 pupal case under clod of earth. 



The eflEiciency of the traps on the cages was tested. One cage was 

 set up as it had been in the field, 20 moths were placed under it in 

 the afternoon, and the paper cover was put on during the night. 

 Only 6 of the 20 moths were found in the trap on the morning fol- 

 lo^ving. This indicates that probably only 30 per cent of the moths 

 that emerged under the cages in the field were caught in the traps. 



One striking point brought out is the difference between the 

 number of moths that emerged and the number of living larvae found 

 in the soil. Table 29 gives an average for the first two examinations 

 in plat 1 of 14 living larvae per square yard. On this plat, in 2 cages, 

 covering a total area of 3 square yards, only 2 moths were caught. 

 If this was 30 per cent of the moths that actually emerged under the 

 cages, there was a total of 6.67 moths, or an average of about 2.2 

 moths, emerging per square yard. 



EMERGENCE OF ADULTS THROUGH SOIL 



An experiment was conducted in the spring of 1922 to determine 

 the depth of soil through which a moth can emerge. Two sets of 

 sheet-iron cylinders were made. These were 5 inches in diameter 

 and closed at the bottom and ranged in depth from 4 to 20 inches. 

 Larva; in cocoons from the soil and in cottonseeds were placed in 

 the bottoms of the cylinders and covered with soil to difl'erent depths 

 (see Table 30). The cylinders were taken to the field and sunk in 

 an upright position in the ground so as to leave the surface of the 

 soil in the cylinder on a level with the surface of tlie soil on tlio out- 

 side. Screen-wire traps were made to fit the tops of the cylinders, 

 so that any emerging moths might be caught. 



