Figure 1-23. Grasses in the Great Plains have become 

 adapted to endure the effects of prolonged drought and 

 grasshopper infestations. Grass stalks, cut off by grass- 

 hoppers, have been washed up against low shrubs by recent 

 rains. August, 1936, western North Dakota. 



height, density, growth-form, and succulence of plants influence 

 the selectivity, consequently different species of plants are affected 

 according to the kinds and abundance of grasshoppers that are 

 present in an area. Agropyron smithii may be seriously attacked in 

 some years and places while other species are much less affected. 

 Weedy grasses, including Schedonnardus pamculatus, Munroa squar- 

 rosa, and Bromus tectorum, are attacked by fewer kinds than the im- 

 portant forage species named above. ^° The requirements of grass- 

 hoppers and locusts often vary according to the stage of the life- 

 cycle, as has been shown in East Africa, where the requirements 

 of nymphs, ffedglings, young adults, and egg-laying adults of the 

 red locust are found in mesic vegetation, in which low grass, tall 

 grass, and bare soil alternate — the characteristic mosaic found in 

 all outbreak areas. ^ 



In contrast to the feeding habits of many grasshoppers, weedy 



Ecological Ckaracteristics of Species &. Populations • 49 



