PINK BOLLWORM OF COTTON IN MEXICO. 23 



carpel tissues just beneath the inner wall of the boll. In the latter 

 case they leave brownish, discolored tunnels or burrows resembling 

 the work of young leaf miners. These tunnels, commonly called 

 "railroads," are very characteristic of pink bollworms and when 

 found are sure evidence that a boll is infested. They disappear as 

 the boll grows older and are not noticeable in an open boll. 



When the larvae cut directly through and into the lint sometimes 

 a. slightly discolored proliferation resembling a puncture made by 

 a cotton stainer is formed and at other times only a slight discolor- 

 ation is left. Again, a larva may be found inside a boll and no sign 

 of its entrance place found even when the boll is examined from the 

 inside. The larvae may tunnel in the carpel tissues or feed in the lint 

 in any direction from the point of entrance and seldom if ever feed 

 on seed until after the first molt. They may burrow between or 

 cut through the fibers of the lint for a considerable distance while 

 feeding on the soft tissues, leaving behind slightly discolored trails 

 through the lint and "railroads" through the immature seed coats; 

 or, on the other hand, they may remain feeding on the lint near the 

 point of entrance. 



Second or third instar larvae are found which seem to have fed 

 exclusively on the lint, but there is always some feeding on the seed 

 before the larvae become fully mature and second and third instars 

 are frequently found in the seed. The seeds are normally first 

 attacked from the broad end nearer the outer surface of the boll. The 

 contents of the first seed attacked are not eaten completely out 

 before an adjoining seed is attacked. The number of seeds attacked 

 by a single larva varies greatly, due to the age and development of 

 the boll at the time of attack and the behavior of the larva. Cases 

 have been seen where a larva completed its development on as few 

 as two seeds and within a short distance of the place of entrance, 

 while another larva may destroy a whole lock or more. Often a 

 larva will cut through the partition into the adjoining lock instead 

 of going to another seed in the same lock. The hole in the partition 

 is clean cut, round or oval, and is good evidence that a pink bollworm 

 has been in that boll. Plate III, B shows these holes. 



When very small bolls are attacked by larvae working downward 

 from the flowers, they turn brown and usually drop from the plants, 

 but if the bolls are not attacked till about half grown, the presence 

 of larvae does not cause them to shed. When there are only 2 to 4 

 larvae in a boll that is rather far advanced, say three-fourths to full- 

 grown, when attacked, the work may be classed as "clean," but if 

 several larvae have attacked a boll that has not reached that stage, 

 the entire contents are very likely to be completely broken down 

 into a decayed mass. The presence of larvae in bolls does not prevent 

 other larvae from entering, and usually larvae of all stages are found 



