128 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



stems of the field, but it is most effective when practised in the pro- 

 gressive or rotation form now used by many farmers. This method, 

 which consists in dividing the field and turning all the animals into 

 each enclosure in turn, meanwhile allowing the others to grow up, 

 gives a greater yield of forage than the old way, and, what most inter- 

 ests the entomologist, permits the weevils to place their eggs at a 

 considerable distance above the ground, where they are almost sure 

 to be destroyed by the live stock at their next admittance to the en- 

 closure. Experience shows that the weevils will deposit their eggs 

 as near the ground as they are compelled, by the shortness of the 

 growth, to do, while there is a limit to the closeness to which animals, 

 particularly cows, can crop their pasture. Fields which have been 

 pastured closely therefore sometimes suffer as much from the pest as 

 do those which are unpastured, while fields pastured in rotation almost 

 uniformly escape with little damage to the first crop and are practically 

 free from weevils when the stock is removed after the egg laying season. 

 Thus the first crop is without labor and the field is, without extra 

 expense or effort, left in condition to produce later crops of hay. 



Harrowing 



In case neither spraying nor pasturing has been employed, the con- 

 dition of the field after the removal of the first cutting is serious. All 

 the larvae and young weevils which made such inroads upon the first 

 crop as to compel its cutting before maturity to prevent total loss, are 

 then compelled to find food in the little sprouts upon the stubble. 

 Although many become ineffective by pupation and many more by 

 death from extreme heat, there are enough left to destroy all growth 

 throughout the time usually occupied by the production of the second 

 crop, which is thus a total loss. Any treatment of the field after the 

 first cutting is a deplorable necessity, because that is the busiest time 

 of the season, and labor and time are valuable, but if no earlier treat- 

 ment has been applied it is simply a question of whether the crop is 

 worth the cost of saving it. 



Under such circumstances the insects can be destroyed and the crop 

 protected by taking advantage of the fact that a temperature of 120° 

 F. is fatal to the insects. This temperature is best produced by cover- 

 ing the surface of the field with something approaching a dust-mulch, 

 unshaded by clods and vegetation. On a bright, warm day such a 

 surface is heated by the sun enough to kill all stages of the weevil, 

 and the dust kills many of those which escape the heat. If the field is 

 not dry, the necessary temperature cannot be produced, and if it is too 

 grassy, rocky or hard, the cost of the preliminary cultivation will be 

 high. The tools used are the disc or spring-tooth harrow and some 



