CLASSIFICATION AND DESCRIPTION OF COMMON INSECTS 299 



6. Muriate of potash. 



7. Lime. 



8. Chloride of Hme. 



9. Gas Hme. 



The results of these experiments showed that as insecticides most 

 of these substances are of very doubtful value. Such a large 

 amount would have to be used in many instances as to completely 

 destroy all vegetation; and the cost would be so excessive as to make 

 their application impracticable. 



The following methods were found of value: 



1. Trapping the wireworms and beetles by means of lanterns, 

 and in some cases by means of poisoned dough placed under boards 

 in infested spots. 



2. Plowing late in fall and keeping the earth stirred more or less up 

 to the time winter sets in. By this means large numbers of the newly 

 transformed pupae, which do not become fully hard until spring, are 

 destroyed. It must not be supposed, however, that all of the wire- 

 worms are killed by such treatment, for the ordinary wireworms spend 

 from 3 to 5 years in the ground feeding on the roots of plants before 

 they appear as adult beetles. It is only when the wireworms are 

 transforming into pupae in the fall that they are very sensitive to dis- 

 turbance of any kind. When the worms are numerous in small areas, 

 especially in spots on low, poorly drained land, they may be easily 

 trapped by placing under boards bunches of clover or sweetened bran 

 poisoned with Paris green. 



3. A short rotation of crops, in which the fields are not allowed to 

 remain more than two seasons in grass land, will be found very effective. 

 It is frequently observed that wireworms are more destructive during 

 the second season after the sod is plowed up than the first. This is 

 because there is sufficient vegetable matter in the soil during the first 

 season to furnish a plentiful supply of food; but with the gradual rot- 

 ting of the soil from another season's plowing the food is removed and 

 wireworms then take to the roots of the growing plants. With the 

 breaking up and thorough working over of grass land in the fall, much 

 of the old vegetable matter may be destroyed (see Part IV). 



4. By the application of mineral fertilizers, it is often possible to 

 force the crops in the following season in spite of the wireworms. 

 (Consult Bull. S3, Cornell; Bull. 44, 111. Agr. Exp. Stn.) 



