348 THE LOCUST 



They are stiffened by thickened portions, or "veins," between 

 which the wing is thin and membranous. In the majority of 

 flying insects the wings are much more dehcate than in the locusts. 

 The external openings of the respiratory system appear as the 

 paired spiracles (Fig. 177), on either side of the three thoracic 

 segments and on the eight anterior abdominal segments. In 

 many insects the margins of these openings are colored, appearing 

 as conspicuous spots along the sides of the body. The number of 

 spiracles differs in insects, but there is typically a pair for each 

 segment of the thorax and abdomen. In Ufe, they may be seen 

 rhythmically opening and closing with the respiratory movements 

 of the body. 



The following sense-organs may be easily recognized in the 

 locust: the compound eyes; the three simple eyes, or ocelli, forming 

 a triangle on the anterior surface of the head; the antennoe, which 

 are tactile and olfactory; and the tympanic membrayies, supposedly 

 auditory in function, which are located latero-dorsally on either 

 side of the first abdominal somite (Fi,-?. 177). 



General Activities. — Grasshoppers are active only in the day- 

 time, although their relatives, the crickets and katydids (Fig. 191, 

 p. 373), are nocturnal hke many other insects. With the com- 

 ing of nightfall the grasshopper remains quietly attached to 

 the vegetation until the sun warms it into the renewed activities of 

 another day. Since the grasshoppers have been extensively 

 studied in attempts to combat them as foes of growing crops 

 (Fig. 172), a brief account of their habits and hfe cycles, as i elated 

 to agriculture, will be given. 



Along the eastern approaches to the Rocky Mountains, for 

 example, injurious grasshoppers may be grouped into two types, 

 the migratory and the non-migratory species. The more serious 

 injury to vegetation is usually caused by the migratory forms. 

 This latter type, of which the " warrior " grasshopper (Cam- 

 nula pellucida) is the most important species now that the Rocky 

 Mountain locust has become virtually extinct, breeds in one 

 locahty and migrates to another. The non-migratory type, which 

 includes all the common species, usually spends its entire life within 

 the radius of a single field or, at most, in a very restricted area. 

 Thus, a farmer who knows nothing of grasshopper control, or one 

 who is indifferent, may breed the local plague that consumes his 

 own fields and also those of his immediate neighbors, whereas 



