22 



Miscellaneous experiments. — The habit of the differential to remain 

 along sloughs, ditch banks, etc., suggested the scattering of lime, 

 acid phosphate, kainit, and other substances to check the march of 

 the grasshoppers out into the crops; but, as none of these materials 

 proved of any value, a continuation of this line of work was early 

 abandoned. 



We found it advisable not to destroy cockleburs growing in the 

 vicinity of the egg areas, as this plant is the favorite food of young- 

 grasshoppers and serves to congregate them, which not only renders 

 more available effective remedies, but also preserves the stand of corn 

 and cotton in these localities. Where it is possible, we also recom- 

 mend delaying the cutting out of the crops to a stand until the young 

 hoppers have been destroyed by some or all of the remedies stated 

 above. 



NATURAL ENEMIES. 



Aside from the very timely rainfall during the latter part of May 

 and in June, there were many predatoiy and parasitic enemies found 

 common to the differential locust in the Mississippi Delta. 



Fig. 6.-— TromMdium locustarum : <i, female with her batch of eggs (from Emerton); b, newly hatched 

 larva— natural size indicated by the dot within the circle; c, egg; d, e, vacated eggshells (from 

 Riley). 



Upon the eggs. — Three predatory and two parasitic 'forms were 

 found feeding to a greater or less extent upon the eggs. 



The locust mite, TromMdium locustarum (see figs, tf and T), which 

 occurs throughout the United States and Canada was in evidence m 

 the Mississippi Delta. The full-grown mites, as well as bunches of 

 the small red-colored eggs, were commonly seen during the cultivation 

 of the land in April and May. While most abundant in the vicinity 

 of the egg-beds, it was not uncommon to find them anywhere over the 

 entire plantation. Many were placed in breeding cages where quan- 

 tities of eggs of differentialis and of other species were kept, but 

 we were disappointed somewhat in not finding them more ravenous 

 feeders upon grasshopper eggs. From the statements of other observ- 



