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



in the same boll. During the latter part of the season, when the 

 infestation is heavy, an average of 6 or 7 larvae is found per boll and 

 individual bolls may contain many more. One boll was examined 

 that contained 26 larvae. The number for all bolls examined through- 

 out the season of .1919 averaged 2.5. 



PROLIFERATION OF BOLLS. 



The presence of larvae often causes the bolls to form abnormal 

 growth or proliferation. Proliferation is described by Dr. W. E. 



Hinds (1) as: 



The development of numerous elementary cells from parts of the bud or boll which 

 are themselves normally the ultimate product of combinations of much more highly 

 specialized cells. The resulting product is thus composed of comparatively large, 

 thin-walled cells, which are placed so loosely together that the resulting formation is 

 of a soft texture, and has a granular appearance which may be plainly seen with the 

 unaided eye. 



Greenish white or discolored brownish opaque swellings are formed 

 on the inner wall of the carpel, the seeds themselves proliferate, 

 and very little if any lint is formed on them. This spongy mass of 

 granular cells develops much more rapidly than lint, thus occupying 

 the space that would have been filled with lint. Badly proliferated 

 bolls contain but little lint, and this is matted or felted and of poor 

 quality, thus greatly increasing the damage done by the pink boll- 

 worms. Proliferous seeds are not confined to those actually attacked 

 by the larva?. The irritation caused by the presence of the larvae in 

 a boll or the stimulation from proliferation in seed actually injured 

 causes other healthy seed to proliferate. The percentage of proliferous 

 bolls increases very rapidly with the advance of the season, which is 

 simultaneous with the increase of the number of bolls attacked by 

 the pink bollworm and with the number of larva? in each boll. The 

 Egyptian cotton grown at the laboratory was much more severely 

 affected by proliferation than were the short-staple varieties. Larvae 

 occasionally are killed by proliferation, but from general observa- 

 tions it is thought that not more than one-tenth of 1 per cent are 

 killed in this way. The result is by far more detrimental than 



beneficial. 



DAMAGE CAUSED BY THE PINK BOLLWORM. 



The damage by the pink bollworm is caused by the feeding of 

 the larvae on the squares and blooms, the walls and partitions of 

 the bolls, and the lint and seed of the cotton. Upon entering the 

 boll after hatching the larvae feed on the lint and tender tissues of 

 the boll during its earlier stages of growth; in the latter stages the 

 larvae feed almost exclusively on the seed, thereby arresting the 

 development of the lint and seed and also destroying the seed itself. 

 In passing from seed to seed and from lock to lock the larvae cut and 



