292 JOURNAL OF ECON OMIC ENTOMOLOGY [Vol. 14 



SOME FACTORS INFLUENCING THE EFFICIENCY OF GRASS- 

 HOPPER BAITSi 



By A. L. Ford and W. H. Larrimer, Scientific Assistants, Bureau of Entomology , 



West Lafayette, Indiana 



Important considerations in grasshopper control have always been, 

 the best poison to use, the proper strength at which to include it in the 

 bait, and the rate of application of the mixture over the infested area 

 in order to obtain a maximum kill. In order to obtain information 

 on these points a series of experiments were conducted during the sum- 

 mer of 1919 at Lafayette, Indiana in fields infested with grasshoppers, 

 of which at least 99% were Melanoplus femur-rubrum. Preliminary 

 to this work the maximum daily feeding period was found to be from 

 8:30 A.M. until 12:30 p.m. (Daylight saving time). It was also nec- 

 essary to determine which syrup would prove most attractive to grass- 

 hoppers. The experiments as here reported can be grouped according 

 to the following outline :- 

 ist. To determine the comparative efficiency of various syrups when 



used under field conditions. 

 and. To determine the optimum strengths of various arsenical sin bran 



mash. 

 3rd. To determine the optimum rate of application per acre for poi- 

 son bran mash. 

 4th. Having found the optimum strengths and rates of application 

 for the various arsenical?, to determine which of them is most 

 efficient when used under its optimum conditions. 



Method of Obtaining Percentage of Kill 



In estimating the percentage of grasshoppers killed by poison bran 

 mash, practically all workers on this subject have merely covinted the 

 number of dead hoppers per unit area of groimd and estimated the 

 number of living hoppers remaining. The writers believe that this is 

 riot an accurate method for two reasons. 1st. It is impossible to even 

 estimate acctuately the number of living grasshoppers per unit area 

 because of the unusual activeness of this group of insects. 2nd. To 

 count the niimber of poisoned hoppers per unit area is inaccurate since 

 not only many hoppers enter cracks in the soil or seek low shady places 

 to die, but other insects and birds consume or carry away many of them 

 before a coimt can be made. 



'Published by permission of the Secretary of Agriculture. 



