PINK BOLLWORM OF COTTON IN MEXICO. 

 Table XIX. — Mortality oflarvse of P. gossypiella. 



39 



Num- 

 ber of 

 plants. 



On plant. 



Number of 

 larvae. 



Pupae 

 found. 



Exit 

 holes. 



Larvae, 

 pupae, 



and 



exit 

 holes. 



Per 

 cent 

 mor- 

 tality. 



Remarks. 



Num- 

 ber of 

 shells. 



Num- 

 ber of 

 eggs. 



In 



squares. 



In 

 bolls. 





181 

 141 

 190 

 170 



103 



89 

 111 

 115 



53 

 143 



3 

 1 

 6 

 

 2 



17 

 46 

 84 

 25 

 39 





 

 

 3 

 



7 



12 

 24 

 13 

 15 



27 

 59 

 114 

 41 

 57 



85.1 

 58.2 

 40.0 

 75.9 



44.7 



16 bolls on plant. 

 28 bolls on plant. 



5 



785 



511 



12 



211 



3 



72 



298 



62.1 



From this table it is seen that the mortality varies from 40 to 85.1 

 per cent with an average of 62.1 per cent. If it -is assumed that 

 none of the larvae from the 47.1 per cent of the eggs laid on other 

 parts of the plants ever succeed in entering the bolls or squares, this 

 would still leave 15 per cent of the larvae from eggs laid on the squares 

 and bolls unaccounted for. Since many eggshells had undoubtedly 

 fallen from the plants examined, this percentage of mortality (62.1 

 per cent) is smaller than what actually occurs. 



To determine what percentage of the eggs laid on the bolls are 

 lost, 16 samples of 25 green bolls each were examined, the number of 

 eggs laid on them counted, and the total infestation found (Table 

 XX). 



Table XX. — Mortality of pink bolhuorm larvae from eggs laid on bolls. 





Eggs. 



Larvae. 



Exit 



holes. 



Pupae. 



Total 

 infes- 

 tation. 



Per cent 

 of larvae 



Number of bolls. 



Tip. 



Base. 



Total 



First. 



Second . 



Third. 



Fourth. 



from 

 eggs laid 

 on bolls 

 recovered 

 in bolls. 



400 



61 

 0.15 



4,958 

 12.4 



5,019 

 12.5 



190 

 0.47 



347 

 0.87 



442 

 1.1 



1,005 

 2.5 



386 

 0.96 



1 



2,371 

 5.92 



45.8 











There were 5,019 eggs and eggshells on the bolls. If larvae from 

 all these eggs had hatched and all the larvae gone into the bolls, there 

 would have been an average infestation of 12.5 larvae per boll, whereas 

 an average of a little less than 6 larvae was actually found. These 

 examinations were made in October and later examinations showed 

 that the maximum infestation ever reached was an average of 7 per 

 boll. 



These figures indicate that about half of the larvae from eggs laid 

 on the bolls themselves never succeed in entering them. In Table 

 III it was shown that 51.7 per cent of the eggs were laid on the boils 

 and appendages, and if only half of these successfully enter the bolls 

 this would be equal to 25.8 per cent of the total eggs. This loss of 



