GRASSHOPPERS — GURNEY AND BROOKS 21 



different areas is largely the result of surrounding conditions. Even- 

 tually, studies may show that the recognition of additional named 

 segregates is desirable. 



The dorsal valve of the aedeagus may have a narrow anterior flap 

 and a rather shallow lateral concavity (figs. 2 J; 3,e), or approach the 

 more swollen type found in intergrades with defectus (fig. 3,/), with 

 wide anterior margin and deep lateral concavity. Practice is re- 

 quired to become familiar with the variation, which apparently is 

 partly individual and partly geographic. A very small male with 

 abortive wings, collected at Clark,|Wyo., Aug. 7, 1937, has the dorsal 

 valve rather stubby, without the usual details, and apparently im- 

 perfect because of the failure of the individual to develop normally. 



Figure 4. — Distribution of male specimens of Melanoplus viexicanus examined. 



The distribution of males of bilituratus hilituratus examined is shown 

 in figures 5 and 6. 



Biology and economic importance: The great importance of M. 

 hilituratus hilituratus, which represents the northern subspecies of what 

 usually has been called M. mexicanus or M. atlanis, is well known. 

 Important bulletins dealing with this grasshopper are by Herrick and 

 Hadley (1916) and by Shotwell (1930, 1941). Although crop and 

 range damage occur most often west of the Mississippi River, injury 

 on a smaller scale occurs in the Eastern States. Washburn (1953) 

 described a severe outbreak on two farms near Palmer, Alaska, in late 

 July 1951, in which populations up to 300 per square yard were 



