t^ocasT 



417 



and low-growing plants of the fields and open country. In the 

 United States many destructive species are found. As early as 1743 

 Mr. Smith reported the damaging activities of Melanoplus atlanis 

 in the New England states, and from 1855 to 1877 many outbreaks 

 of grasshoppers were reported in the western United States. Even 

 today the national government is expending large sums annually 

 to keep down the activities of the many destructive species. 



The grasshopper is a typical insect, and may serve to illustrate 

 the general structure of the class Insecta. 



13 1.4 15 16 



Fig-. 171. — External features of a grasshopper. 1, maxillary palp.; 2, mandible; 

 S, labrum ; .',, clypeus ; 5, f rons ; 6, compound eye; 7, ocellus; 8, vertex; .0, antenna; 

 10, gena ; 11, pronotum ; 12, wing, mesothoracic ; IS, spiracle, thoracic; U, spiracle 

 of first abdominal segment; 15, auditory apparatus; 16, wing, metathoracic ; 11, 

 supra-anal plate; 18, podical plate; 19, cercus ; 20, ovipositor; 21, labial palp; S2, 

 femur of prothoracic leg; 23, coxa of metathoracic leg; 2Jf, trochanter; 25, femur; 

 26, tibia; 27, tarsus; 28, femur of metathoracic leg; 29, spiracle; 30, sternum; Si, 

 tergum. (Courtesy of General Biological Supply House.) 



The insect body is divided into a series of rings, or segments, and 

 the segments are made up of hardened plates. These plates are 

 known as sclerites, and the depression between the plates is called a 

 suture. The hardness of the plates is due to the deposition of a 

 horny substance called chitin. In many places two or more of these 

 rings have grown together, or are fused. Again, in certain regions 



