OUTLINES OF ENTOMOLOGY. 113 



CHAPTER XXVIII. 

 Order VI. OKTHOPTERA. 



[Fig. 45.] 



Old World Migratory Locust (Pachytylus migratorius.) 



In this Order of so-called straight-winged insects we find many 

 unusually interesting species. Geologically and historically they are 

 the oldest of insects. In the stratified rocks their remains are found 

 among the very earliest forms of animal life ; while the " locusts,' 7 so 

 frequently mentioned in the Old Testament, and in equally ancient sec- 

 ular history, as suddenly swooping down upon a country and "devour- 

 ing every green thing," are among the typical representatives. Except- 

 ing the Cicadas, described in a preceding chapter, we find among the 

 Orthoptera the only insects provided with a special musical apparatus, 

 each species having its own peculiar instrument and contributing its 

 characteristic notes, called stridulations, to the insect concerts that 

 enliven the summer days and nights. Many of the most singular imi- 

 tative forms that occur in nature are also found here in the " walking 

 sticks" and "walking leaves" that compose one of the groups; and 

 by many other peculiarities of structure and habit the Orthoptera chal- 

 lenge attention from the student of pure science, the lover of nature, 

 and the economist. 



The straight-winged insects are nearly all of a size to be examined 

 without the aid of a microscope, and some forms have been considered 

 superior to all others as subjects for dissection in the study of internal 

 as well as external structure. While they exhibit much variation in 

 form, all the more conspicuous species agree in the vertical position of 

 the head, the biting mouth, the large pro-thorax, and the parchment-like 

 wing-covers when these organs are present. 



The head is usually large, and though somewhat sunken under the 

 pro-thorax in many species, is freely movable on the flexible neck. The 

 eyes are round or oblong, and prominent in most species. The antennae 



