320 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



marized briefly here, made her feel fairly certain that the grasshoppers 

 originated in western Morocco, where they probably left the morn- 

 ing of October 11, arriving over Portugal late that night or the next 

 day. The distance involved was 600 to 800 miles, varying with dif- 

 ferent localities in Portugal where they were found. Very complete 

 information on grasshopper movements in Africa was available, and 

 the nearest reported swarm of a comparable age, the degree of sexual 

 maturity after the final molt in that species being shown by color, was 

 in western Morocco. On the morning of October 11 there was a sharp 

 rise in temperature, which presumably would induce flight activity, 

 accompanied by convection currents and a wind blowing out to sea. 

 A few miles offshore a strong wind from the south, averaging about 

 30 miles per hour at 1,500 to 2,000 feet, was also recorded by meteor- 

 ologists. The facts in this case are unusually complete, due in large 

 part to the existence in Africa of a well-developed organization for 

 compiling data related to migratory grasshoppers. 



The occurrence of gr eg aria in Portugal is not new, Uvarov (1928, 

 p. 253) referring to its occasionally being found there and conclud- 

 ing that "it seems certain that in all cases the appearance of the 

 locusts has been due to strong swarms from Africa." 



There are numerous recorded cases of long flights by Schistocerca 

 gregaria. Scudder (1878) and Howard (1918) give separate in- 

 stances of its being taken on board ships in the Atlantic Ocean about 

 1,200 miles from the African mainland. Uvarov (1923, pp. 34-35) 

 reports specimens of gregaria from the islands of Cape Verde, Grand 

 Canary, and Ascension, and he says those occurrences can be explained 

 only as the result of flights from Africa. Swarms of gregaria usually 

 travel about 20 to 30 miles per day, and settle down at night (Waloff, 

 1946), so these unusually long movements are of interest in illustrat- 

 ing the potentialities of migratory grasshoppers when aided by espe- 

 cially favorable weather conditions. 



FACTORS INFLUENCING THE MOVEMENT OF GRASSHOPPERS BY AIR 



Some basic principles bearing on long flights of grasshoppers have 

 been treated in recent publications based on field work with the desert 

 locust in Africa and the Middle East. J. S. Kennedy (1951) has 

 analyzed the various factors involved in the behavior of swarms, and 

 has presented a theory explaining long-range migrations. The chief 

 factors are the condition of the grasshoppers, gregariousness, wind, 

 sun, and landscape. The influence of wind was stressed, since swarms 

 of gregaria usually fly into the wind by choice. If the latter is too 

 strong, however, as is often true when it blows about 9 miles per hour 

 or more, the grasshoppers are apt to turn aside. Then they most 

 often settle or turn about and fly with the wind. Rainey and Waloff 

 (1951) have given special attention to the effect of convection cur- 



