46 



BULLETIN 918, U. S. DEPARTMENT OF AGRICULTURE. 



in the seed warehouses, because the dead larvae are so hard to find, 

 but it is evident to one collecting larvae that it is much higher in 

 the early spring than in the fall. The mortality was 80 per cent 

 among larvae thrown out by the cleaners and stored indoors during 

 the winter, and in this sample only the most active larvae were used. 



Table XXIII. — Mortality among larvae in double seeds removed from lint by hand and 

 stored in jars in the laboratory. 



Date collected. 



Number 



entering 



resting 



stage. 



Number 

 emerged. 



Per cent 

 mortality. 



Per cent 

 emerged. 



Number 



alive Nov. 



20, 1919. 



1918. 

 Nov. 15 



206 

 190 

 184 

 88 

 61 

 213 



172 



182 

 165 

 157 

 76 

 41 

 119 



143 



8.7 

 9.4 

 8.1 

 9.0 

 22.9 

 41.3 



11.6 



88.3 

 86.8 

 85.3 

 86.3 

 67.2 

 55.8 



83.1 



6 

 7 



12 

 4 

 

 6 



9 



Nov. 22 



Nov. 23 



Nov. 22 



Do 



Dec. 25 



1919. 

 Jan. 23 



Total 



1,114 



883 







50 

 4.4 per cent. 



16.2 



79.2 









MORTALITY OF LARVAE PLANTED WITH THE SEED. 



A screen-wire cage was built so that no infestation could interfere 

 from the outside, and 100 double seeds were planted with sound 

 seed in 30 hills to see what the infestation would be from larvae 

 planted with the seed alone. No infestation occurred during August, 

 but from September 1 to November 7 the infestation went from 

 12 per cent to 96 per cent, with an average of 5.6 larvae per boll on 

 November 7. Thus it is evident that should all the larvae left in 

 the fields be destroyed either naturally or by artificial means, the 

 infestation arising from the larvae planted with the seed alone is 

 sufficient to cause a considerable loss (Table XXIV). 



Table XXIV. — Infestation of pink bollworm from 100 double seeds planted in a cage. 



Date examined. 



Per cent 

 of bolls 

 infested. 



Average infestation per boll. 



Larvae. Pupa?. 



Exit holes. 



Total. 



1919. 

 Aug. 1 















12.00 

 84.00 

 96.00 















0.12 



2.20 



5.60 





 

 

 

 

 



















0.96 



















0.12 



3.16 



5.60 



Aug. 6 



Aug. 22 



Sept. 1 



SeDt.30 



Nov. 7 





PARASITES AND PREDATORS. 



What part of the mortality in the newly hatched larvae is due to 

 starvation, exposure to the sun, or falling from the plants, and 

 what to predacious insects, could not be determined, but the toll 



