50 THE ORTHOPTERA OF MINNESOTA. 



The phosphoric acid in such phosphates as are insolu- 

 ble in water or solution of ammonium citrate of 1.09 specific 

 gravity is termed insoluble phosphoric acid; in such as are 

 insoluble in water but soluble in ammonium citrate solution 

 is termed reverted phosphoric acid. "Soluble" and "re- 

 verted" phosphoric acid are equally available by the plant 

 as food. Insoluble phosphoric acid is not as readily avail- 

 able. Nitrogen is the most valuable fertilizing ingredient." 



CONCLUSION. 



It is possible to successfully fight and exterminate lo- 

 custs, providing active measures are adopted at once, and 

 are, moreover, carried out faithfully. This is only true, 

 however, if we have to deal with local swarms, and not 

 with armies covering whole states. In the former case if 

 every one owning a farm in the infested region will only 

 properly cultivate the same, will plow it during the fall, 

 permit no fields to be idle, and seed it in the spring, no fears 

 of loss need be entertained. 



In describing the habits of insects, their growth and 

 metamorphoses, as well as their relation to agriculture, hor- 

 ticulture and allied pursuits, it is ver\' important and neces- 

 sary to study not alone the general form of an insect, but also 

 its external and internal anatomv. For our purpose it will 

 be suflficient toselect one member of the order of orthoptera, 

 the common Two-striped Locust [Melanoplus bivittatus), 

 and to describe in as general terms as possible the different 

 parts of the same. 



