720 



present in South Africa are : Lociista pardalina (brown locust), 

 and Cyrtacanthacris septeiiifasciata (red locust). Locusta danica 

 and Schisfocerca {Acridium) peregrina, which also occur in 

 S. Africa, are northern migratory forms. L. pardalina is an 

 inland species, occurring on grassy plains. The Kalahari Desert 

 seems to be the starting point' of swarms, which travel in all 

 directions, to the east to Rhodesia and the Transvaal, and to the 

 south to the Cape and the Orange River Colony Provinces. In Natal 

 and the Cape VvoYmceC.sejjtemfasciafo, is essentially a coast-frequenting 

 insect, but has also been found far inland. This species shows a 

 preference for arboreal vegetation and this suggests that its permanent 

 abode is not in the Kalahari Desert. The brown locust appears on 

 the wing in March or later and deposits its eggs before winter. The 

 eggs hatch in October and the insects become winged two months 

 later. Two generations occur annually, the first corresponding with 

 the spring rains, the second from 3 to 5 months later. Moisture is 

 required for the development of the egg, which can, however, retain 

 its vitality for more than one season. The red locust has probably 

 only one generation annually ; there is no evidence to show that 

 sggs retain their vitality into a second season, or that rains are 

 essential for their development. Egg-laying in Natal usually takes 

 place early in December, and hatching follows in about 30 days. 

 In the Cape Province, egg-laying may be prolonged into February 

 and March. The locust problem in South Africa is associated with 

 the occurrence of tracts of arid country where the rainfall is scanty 

 and erratic. The gregarious, migratory locust, capable of long- 

 sustained flight, appears to be a natural development in such a 

 situation. The author believes that locusts are continually present in 

 arid regions. The brown locust is supposed to be permanently resident 

 in Kalahari, Bushmanland, Griqualand West, the eastern half of the 

 Orange River Colony and the northern and central parts of the Cape 

 Province. The excessive multiplication may be correlated with an 

 abundance of food supply, which in its turn is dependent on the 

 cyclical climatic change in the region where the insects have their 

 permanent home. 



From personal observation, the author has become impressed with 

 the fact that locust visitations have closely followed long droughts 

 which have been terminated by widespread and general rains. The 

 sudden appearance of the brown locust may be explained by the fact 

 that the eggs preserve their vitality for years in the absence of adequate 

 moisture and accumulate in numbers during this time. Return 

 migrations may be due to wind movements and not to inherent 

 inclination. Birds seem to be a great factor in locust suppression in 

 S. Africa. The most important are Ciconia alba and Glareola melan- 

 oplera, both migrants from the northern hemisphere ; these arrive in 

 October and November and depart during March. The progressive 

 multiplication of locusts is only possible when these birds come to the 

 country in small numbers. Other parts of Africa are subject to locust 

 visitations, and to reach the south, the birds must traverse the continent 

 from the north-east. If there is a shortage of locusts in one region, 

 the birds may pass on to another where the insects are more abundant ; 

 locust cycles in one region may therefore alternate in some measure 

 with those of another localitv- 



