THE INSECT ENEMIES OF THE 

 COTTON BOLL WEEVIL. 



INTRODUCTION. 



When the cotton boll weevil first entered the United States it 

 appeared to have almost undisputed sway. It did, in fact, escape 

 most of its enemies. But whether parasites were introduced with it 

 or not, we now know that within the first three years of its existence in 

 Texas it was attacked by three important species of parasites. Year 

 after year new factors in its control are becoming apparent, although 

 some have probably been concerned since the beginning. On the other 

 hand, it is certain that entirely new elements are entering the struggle 

 as rapidly as the weevil enters new biological complexes. Among the 

 most striking of these new elements in the control is the recent adjust- 

 ment of Microdontomerus anthonomi Crawford (fig. 9, p. 49) . This spe- 

 cies was unknown until 1906 when a very few were taken in material 

 reared at Cuero, Goliad, Hallettsville, Victoria, and Waco, Tex. 

 In 1907 it was found to predominate in a portion of central Texas. 

 In 1908 its range was found to extend northward to the Red River. 

 In 1909 it was found as far east as the Mississippi River in Louisiana. 

 Only a single record of the occurrence of SigalpJius curculionis Fitch 

 (fig. 11, p. 53), the common parasite of the plum curculio, had been 

 made prior to 1908. In that year it began to make its presence felt 

 in northeastern Louisiana and western Mississippi. In 1908 a new 

 chalcidoid parasite, recently described as Tetrastichus Jiunteri Crawford, 

 was found to be the leading parasite of the boll weevil in northern 

 Louisiana and western Mississippi. In 1909 this species was found 

 as far west as Arlington, Tex. 



With the advent of each new enemy and its more complete adjust- 

 ment, the power for damage possessed by the weevil is by so much 

 diminished. On the other hand, every factor which checks these 

 enemies without also checking the weevil benefits the weevil. 



If the solution of the boll- weevil problem consisted merely in adding, 

 one by one, factors which would cut off a given percentage of the 

 weevils, the time would not be distant when that might be accom- 

 phshed. The problem is far more complicated. The various factors 

 do not discriminate against one another, for while heat, ants, cold 

 weather, and excessive moisture may remove many parasites from 

 the struggle, it also follows that heat, cold weather, heavy rains, 



9 



