October, 'OS] JOURNAL OF ECONOMIC ENTOMOLOGY 32JJ 



lowed to dry and hang. Here the heat is not so great, and the ants 

 are less likely to find the weevil stage within, but the sun-loving Hy- 

 menoptera choose this situation for their attack, in preference to fal- 

 len squares. Certain varieties of cotton mature very early, and hence 

 drive the weevils out sooner. Some varieties have less extensive foli- 

 age than others and hence permit greater mortality from the sun's 

 rays. Under some conditions proliferation also destroys the immature 

 stages by crushing. Examples of these kinds abound throughout our 

 literature. The protection afforded insects by the plant is often a 

 great protection against manj^ factors, e. g., the protection of cotton 

 bolls compared with squares. The thickness of the carpels and the 

 mass of the fiber in the bolLs afford considerably more protection 

 against cold than the squares. 



3. Cultural conditions. Insect control is frequently effected by 

 means of certain cultural or field practices. In the boll weevil prob- 

 lem it is possible to make parasite control supplement this cultural 

 control, as has been shown in my paper, previously quoted. Our idea 

 is to kill all of the boll weevils that can be killed, and to do this Ave 

 must add every factor, which can do even a little bit. The parasites 

 can take a given per cent which can not be touched by any given cul- 

 tural method and furthermore are facilitated in part of their work 

 by definite cultural practice. 



4. Food supply. In a general way the amount and nature of the 

 food supph' of an insect determines its size, its fecundity, its ability 

 to withstand climatic conditions, the rapidity of development, and its 

 movements. The food supply is in turn controlled by climate. 



5. Duplicated mortality. It goes without demonstration that, with so 

 many factors of mortality possible in the case of a given insect, there 

 will be more or less duplication. Ants carry off the evidence of mor- 

 tality by both heat, fungus and parasites. Parasites attack and breed 

 upon hosts already killed, and upon those which would have been 

 killed by other factors. Heat kills stages which would have been 

 otherwise killed, and in fact kills these other agencies also. Never- 

 theless it must be considered that, whether a parasite was needed or 

 not in order to kill a given stage, having done so it is capable of pro- 

 ducing offspring which may be of direct and positive value. 



