118 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



of eggs and very young larvae killed by the proliferation of plant 

 tissue. These were gathered at many places over an area of approx- 

 mately 200,000 square miles, at many times and are representative of 

 all the component biological or geographical regions infested by the 

 boll weevil in the United States. 



During 1907 the average control of the weevil by parasites was ten 

 per cent against four per cent in 1906. They are not, however, the 

 principal element of control. Out of 62 per cent mortality in 1907, 

 32 per cent was due to heat and other climatic conditions, while 20 

 per cent were killed by predatory ants. This gives then 30 per cent 

 as the sum of insect control. 



The utilization of these insects belongs in three distinct groups of 

 economic treatment. The most important group consists in the appli- 

 cation of strictly cultural methods to farm practice and is therefore 

 under the control of every cotton grower. The next group takes ad- 

 vantage of the known rotation of hosts and also belongs under farm 

 practice. The third group is the simple introduction of parasites and 

 is really in many cases preliminary to the two preceding. 



The first mentioned group of methods involves early planting, wide 

 spacing, and the use of determinate, short limbed, square retaining- 

 varieties of cotton, as explained in the following paragraphs. 



The study of the activity of the parasites on weevil stages in dif- 

 ferent conditions demonstrated that the most favorable condition for 

 parasite work was the dried hanging square. It appears that when the 

 weevil attacks the squares or bolls the plant produces a corky absciss 

 layer which causes the infested form to fall to the ground. There is 

 a decided tendency among certain varieties and less so in all varieties 

 to fail in forming a complete absciss layer and hence the infested 

 part is caused to hang. When this has become dry, it affords the best 

 possible condition for parasite attack since most Hymenopterous para- 

 sites require heat and light for successful work. During 1907 the 

 average parasite control in hanging squares was 30.45 per cent, in 

 fallen squares 4.67 per cent, in hanging bolls 5.44 per cent, and in 

 fallen bolls 2.5 per cent. This positive demonstration of preference 

 contributes a suggestion for economic application. It may be possi- 

 ble that plant breeders can develop a variety of cotton which will 

 have this tendency in such a marked degree, that the possible parasite 

 control will exceed the total control by all causes in varieties which 

 shed all infested forms. At present the total control in hanging and 

 fallen squares does not greatly differ. 



Careful studies have demonstrated a preference for squares fallen 

 in the sun over squares fallen in the shade, and for fallen squares on 



