22 



BULLETIN 918, TJ. S. DEPARTMENT OF AGRICULTURE. 



turbed by other insects, such as the flower beetle, Euphoria basalis 

 Gorg. If the larva is not full-fed at the time of opening it may 

 continue feeding inside the flower for two or three days or until 

 after the flower has dropped, or it may work downward from the 

 flower into the newly formed boll. No indication of the larva leav- 

 ing flowers and going into large bolls was ever observed, and it is 

 exceptionally rare to find more than one larva in a single square or 

 flower. From June 1 till August 10, 1919, a daily record, with a few 

 exceptions, was kept of the flowers opening on a small plot of heavily 

 infested cotton at Ciudad Lerdo. The results are given in Table X. 



Table X. — Infestation of cotton blossoms by the pink bollwonn. 



Month. 



Number 



of 



days 



counted. 



Infested. 



Non- 

 infested. 



Total. 



Percent- 

 age 

 infested. 



June... 

 July. . - 



August 



226 

 89S 

 967 



S,210 

 12,333 



2,508 



8,436 

 13,231 

 3,475 



2.7 

 6.8 

 27.8 



On October 3, 50 per cent and on November 10, 90 per cent of the 

 flowers on this same plot were infested. This plot was more heavily 

 infested than is normally the case under field conditions. The in- 

 festation is usually highest in June and July, when few large bolls 

 are present on the plants, and decreases during August and Septem- 

 ber. In October and November, when there are many larvae pres- 

 ent and not so many green bolls, the infestation again increases and 

 the few blossoms appearing at this time are heavily infested. As 

 the feeding in the squares and blossoms is largely on the pollen, 

 the presence of a larva does not necessarily prevent a normal boll 

 from forming. Blossoms were tagged in 1919 and it was found 

 that 40.8 per cent of the noninfested squares and 67.6 per cent of 

 the infested blossoms were shed. 



LARV/E FEEDING IN BOLLS. 



That inside the bolls is the most favored feeding place for pink 

 boilworms is shown by the fact that as soon as the bolls are large 

 enough most of the larvae choose bolls instead of squares or flowers. 

 They attack the boll in all stages of its growth, from the time it is 

 the size of a pea until it begins to open, though most commonly 

 it is not entered until about one-half to three-fourths grown. The 

 larvae bore into the boll at any point upon its surface soon after 

 hatching and remain in the same boll mi til ready for pupation. 

 Once the larvae have entered the boll no definite plan of procedure 

 is followed. They "may burrow directly through the carpel and 

 begin feeding on the soft watery lint or they may stop before cutting 

 completely through and burrow for an inch or more in the spongy 



