88 INSECT ENEMIES OF THE BOLL WEEVIL. 



Parasites reared 250 



Parasites escaped. 250 



Parasites in field 500 



There is 1 parasite to every 7.7 weevils. 



III. — Given 10,000 developing stages in a 1 -acre field. 



No squares are collected 10,000 



Normal parasitism, 5 per cent 500 



Ants and heat kill 40 per cent 4, 000 



Mortality 4, 500 



Breed 5,500 



Parasites reared, 500. 



There is 1 parasite to every 11 -weevils. 



SUMMARY. 



ELIMINATION OP COHOSTS. 



Another practice of undoubted value in bringing about a higher 

 percentage of parasitism upon the boll weevil is the eUmination of 

 the cohosts of the boll-weevil parasites at proper times. To show 

 what has been done in this Hne, the case of the Dallas farm in 1907 

 may be cited. On July 19 of that year a very large hedge of weeds, 

 Ambrosia trifida, infested by Lixus scrohicollis was cut. These weeds 

 were along the fence adjoining a part of the cotton field wliich had 

 been under close observation for parasites throughout 1906 and the 

 spring of 1907. In 1906 there was not found in any plat on tliis 

 farm a higher parasitism than 2 per cent by Eurytoma tylodermatis in 

 hanging squares. Eurytoma was very numerous in the Ambrosia 

 weeds next to tliis field, but did not appear to attack the weevil in 

 large numbers. Before the weeds were cut in 1907 the two plats 

 nearest these weeds averaged 26.76 per cent and 16.79 per cent 

 parasitism by Eurytoma. On August 17, about a month after those 

 weeds were cut, the two plats just mentioned had, respectively, 37.50 

 per cent and 26.66 per cent parasitism by Eurytoma. This striking 

 gain adjoining the weeds was not reflected by parts of the field farther 

 removed. 



