86 INSECT ENEMIES OF THE BOLL WEEVIL. 



The figures show that parasitism becoraes very high under favor- 

 able conditions and also that agriculture modifies the insect control. 

 Obviousl}^ therefore those agricultural methods which will favor the 

 highest insect control must be sought. These methods, as now 

 known, will be dealt mth more fully in a follo-s^ing section. 



It was feared for a long time that the parasites of the weevil would 

 be held in control by the warm climatic conditions which affect the 

 boll weevil. This is not so. We have found abundant proofs of the 

 fact that a temperature which vnll kill the boll-weevil larva will not 

 kill the egg or small parasite larva in the same cell, and that the 

 parasites can develop to maturity on the dried remains of the weevil. 

 The temperature fatal to the boll weevil is 123° F., a temperature 

 frequently reached on a hot burning soil. We have found in several 

 years that a low temperature winch mil kill the boU-weevil larva is 

 also not fatal to the parasites, for in November, 1907, when 97 per 

 cent of all the boll-weevil stages were frozen, no evidence whatever 

 could be found of mortality among the parasites. The minimum 

 fatal temperature of the boll weevil is 12° F. 



3. INTEEPRETATIOX OF THE BIOLOGICAL COMPLEX. 



The complicated biological factors which have been noted in Part II 

 have been summarized briefly in section 16 of that part (p. 82). 

 The interpretation of these facts has been suggested in a number of 

 places throughout the second part. Hence only a few words are 

 necessary at this point. 



The fact that surrounding each cotton field there are numerous 

 plants harboring weevils and then' parasites is of extreme importance 

 in this problem. These parasites are generally capable of attacking 

 the boll weevil under conditions of necessity or alternative choice. 

 The aim is therefore to find all the methods by which these parasites 

 may be forced to leave their native hosts and attack the boU weevil. 

 In fact, the entire second part has been devoted to giving these facts 

 ia order to brhig out this single point. 



4. HOW TO PROFIT BY EXISTING COXDITIOXS. 



COLLECTION OF COTTON SQUARES IX SCREENED CAGES. 



As has just been pointed out, there are conditions around the cotton 

 fields which are potential of a considerable uicrease in the parasitic 

 control of the boll weevil. Probably no other method will yield 

 better results than the gatheruig of the cotton squares which are 

 infested and placnig them ia wire-screen cages of 16 or 18 mesh to 

 the inch and placiug these cages in selected parts of the cotton 

 fields. This method is not new in entomological practice. It has 



I 



