128 



Species and Species Change 



ably seldom oscillate synchronously. For example, outbreaks of the 

 African migratory locust Locusta migratoria occurred from 1928 to 

 1934 (Fig. 51), but the occurrence and spread of outbreak areas 



Fig. 51. An outbreak of the African migratory locust Locusta migratoria 

 migratorioides. The area on the middle Niger where the outbreak commenced 

 in 1926-27 is shown in black. The successively numbered areas indicate annual 

 expansion of the invaded area in the period 1928-34. The distribution of low- 

 density areas of the species is not indicated. (After Uvarov. ) 



was highly irregular (Uvarov, 1951). The entire population of sev- 

 eral fur animals show fairly regular oscillations (Fig. 52) (Mac- 

 Luhck, 1937), and moderately large segments of many species 



