468 INSECTS INJURIOUS TO VEGETATION. 



and advised by Mr. Herrick, is the very best method of getting 

 rid of the Hessian fly. It is true that by so doing, many of 

 the numerous parasites of the insect will also be destroyed. 

 But this need not give us any concern ; for if we can succeed 

 in putting a stop to the ravages of the Hessian fly, by these 

 or any other means, we shall not have occasion to mourn the 

 loss of the parasites. It is found that luxuriant crops more 

 often escape injury than those that are thin and light. Steep- 

 ing the grain and rolling it in piaster or lime tend to promote 

 a rapid and vigorous growth, and will therefore prove bene- 

 ficial. Sowing the fields with wood ashes, in the proportion of 

 two bushels to an acre, in the autumn, and again in the first 

 and last weeks in Aprfl, and as late in the month of May as 

 the sower can pass over the wheat without injury to it, has 

 been found useful.* Favorable reports have been made upon 

 the practice of allowing sheep to feed off" the crop late in the 

 autumn, and it has also been recommended to turn them into 

 the fields again in the spring, in order to retard the growth of 

 the plant till after the fly has disappeared.! Too much can- 

 not be said in favor of a judicious management of the soil, 

 feeding oft^ the crop by cattle in the autumn, and burning the 

 stubble after harvest; a proper and general attention to which 

 will materially lessen the evils arising from the depredations 

 of this noxious insect. 



Fortunately our efforts will be aided by a host of parasitical 

 insects, which are found to prey upon the eggs, the larvae, and 

 the pupsB of the Hessian fly. Mr. Herrick states, | that, in 

 this part of the country, a very large proportion, probably 

 more than nine tenths, of every generation of this fly is thus 

 destroyed. One of these parasites was made known by Mr. 

 Say, in the first volume of the "Journal of the Academy of 

 Natural Sciences of Phfladelphia;" and the interesting dis- 

 covery of three more kinds is due to the exertions of Mr. 

 Herrick. They are all minute Hymenopterous insects, similar 



* " Cultivator," Vol. V., p. 59. 



t " Cultivator," Vol. IV., p. 110, and Vol. V., p. 49. 



X "American Journal of Science," Vol. XLI., p. 156. 



