﻿6 BULLETIN 1374, U. S. DEPAETMENT OF AGEICULTUEE 



The great number of punctures counted on the bolls is very striking. 

 These particular bolls were not examined further to determine the 

 number of larvae inside, but three field examinations made on October 

 5, 13, and 20, resj)ectively, gave an average of 5.64 larvae and exit 

 holes per boll. So it may be assumed that the infestation of the bolls 

 on which Table 2 is based was somewhere near this figure. 



In some cases the young larva goes directly through the entire wall 

 of the boll and into the lock of cotton inside. In this case the point 

 where it passed through the inner wall is only slightly raised and may 

 be somewhat colored. Very frequently, after passing through the 

 greater part of the wall of the boll, it tunnels for some distance just 

 underneath the inner surface of the wall. In this case the tunnel 

 usually extends until either the suture or the partition wall is reached, 

 at which point the larva then enters the lock. This tunneling occurs 

 more commonly in nearly mature bolls, where the inner wall is 

 harder. Some of these types of entrances are shown in Figure 3. 



ISSUANCE OF FULLY DEVELOPED LARV^ FROM BOLLS 



In the fall of 1922, a test was conducted in the laboratory to 

 determine the time of the day mature larvae leave the green bolls. 

 Fifty green bolls were placed in a screen-bottom tray, with a trap 

 underneath to catch any emerging larvae. All larvae were removed 

 from the trap each day at 8 a. m. and at 8 p. m. Of 172 larvae taken 

 out of the trap from September 29 to October 17, 160 were removed 

 in the afternoon and 12 in the morning. According to this, the 

 larvae, at least under laboratory conditions, prefer to leave the bolls 

 during the daytime. 



TRANSFORMATION AND HIBERNATION OF THE PINK BOLL WORM IN THE SOIL 



PUPATION DURING SUMMER 



In the Laguna district the pink bollworm passes the pupa stage 

 during the summer in shed blooms and bolls, under or attached to 

 leaves on the surface of the soil, and in the soil. Rarely are pupae 

 found in bolls on the stalks. None were ever found in green bolls. 

 One hundred and seventy-four open bolls on stalks examined during 

 the period from July 7 to November 28, 1921, showed neither pupae 

 nor pupal cases, but a total of 358 larvae and exit holes. The last 

 figure, however, does not represent the total infestation, since larvae 

 issuing from the bolls after opening do not as a rule cut exit holes 

 through the wall. Open bolls on stalks during the latter part of 

 November and in December, 1922, averaged about 8 pupae and pupal 

 cases per hundred. 



VARIATIONS IN NUMBERS IN THE SOIL 



A considerable number of field examinations were made during 

 1921 and 1922 in a study of the transformation of the pink bollworm 

 in the soil. In making these examinations, samples of soil, usually 

 1 square yard to the depth of 6 inches, were taken from heavily 

 infested cotton fields and the number of pink boUworms in each 

 sample determined. The square yard was laid off so as to have a 

 row of cotton running through its middle. The soil was first sifted 

 through a sieve of which the mesh was too small to allow the passage 

 of pink boUworms. The coarse remaining material was taken to the 

 laboratory and washed through other sieves, leaving finally only 



