198 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



which had been sown at the same time. If, as is sometimes the case 

 with citrous baits, an efficient kill has not been obtained within a few 

 days, the materials and labor represent an almost complete loss, whereas 

 with non-citrous fruits the odor becomes stronger, and even when the 

 bait has been completely dried out, a slight mist or dew will cause the 

 non-citrous baits to again become odorous and attractive, and conse- 

 quently not a complete loss, even though the initial kill had not been 

 high. 



Relative Attractiveness of Mature and Immature Grass- 

 hoppers TO Odorous Baits 



As the majority of the grasshoppers recorded in these experiments 

 were adults, the question arises as to whether these baits would prove 

 equally effective against immature grasshoppers. The writer's obser- 

 vations seem to show that the younger hoppers are much more suscep- 

 tible to a highly odorous bait. In three control experiments on July 

 23, at which time a considerable portion of the hoppers were in the 

 third and fourth instar, a very efficient kill was obtained by the addi- 

 tion of half an ounce of lemon extract to the standard formula. It 

 was originally intended to use the lemon fruit alone, but the lemons 

 did not make the mixture especially odorous so the extract was added. 

 This gave a very efficient kill of from 85 to 90 per cent of the infestation. 



In comparison with the above we have the results of four experi- 

 ments on August 6, under approximately the same conditions. Here 

 lemon fruit was used in the standard bait at the rate of five fruits to 

 25 pounds of bran. The hoppers were still in the third and fourth 

 instars with a few adults. The results from these experiments show 

 not more than a 65 per cent mortality, and this included mostly fourth 

 instar and adult hoppers. This difference in efficiency compared with 

 the earlier experiment, which gave a 90 per cent mortality, is marked 

 and would indicate that young hoppers responded better towards the 

 more odorous bait. This suggests that there may be considerable 

 variation between the attractiveness of a certain bait to the younger 

 in comparison with the more mature hoppers. It is believed that had 

 lemon extract been added to the bait in this second series the results 

 would have been much more efficient. 



Effect of Climatic Conditions on the Efficiency of Poison 



Bait 



A rather low temperature and a high humidity such as one finds 

 immediately after a storm, appears to be ideal f ora rapid and maximum 

 mortality. In one experiment an application of four different baits, 

 containing three different poisons, was made following a night of heavy 



