THE EXTERNAL ANATOMY OF A LOCUST. 



Before taking up the description and classification of tlie insects 

 treated in tliis paper, it is thought best to describe briefi}^ the ex- 

 ternal parts of a typical member of the order Orthoptera. The be- 

 ginner may thus the .more readily grasp the name and location of 

 the parts used in classification, as well as the meaning of many of 

 the technical terms which, of necessity, have to be used in such a 

 paper. 



]f we compare the body of a locust or grasshopper with that of any 

 vertebrate animal, as a fish, bird or squirrel, we find at once great 



Body of a locust, side view, showing the thorax separated from the head and ab- 

 domen, and divided into its three segments. 

 (After Packard.) 



and important differences. The vertebrate is an animal with an 

 inner bony skeleton, two pairs of jointed limbs or appendages, and 

 breathes by means of lungs or gills, according as it dwells in air 

 or water. The insect is an animal which has no inner skeleton or 

 bones whatever, but only a hard crust on the surface which sur- 

 rounds the muscles and vital organs. This crust is composed of sep- 

 arate rings, 17 in number, placed end to end. These rings, as well as 

 the legs and wings attached to them, are composed of a cuticle or 

 skin hardened by a substance called "chitin,'" which is secreted or 

 exuded by the cells which compose the cuticle. Chitin itself is in- 

 soluble and is not composed of cells, but consists of fine, irregular 

 plates. It hardens the cuticle and thus aids the latter in protecting 



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