218 Journal of the Department of Agriculture. — Sept., 1922. 



LOCUSTS: SEASON 1921-22. 



Report by R. H. Williams, Officer-in-Charge, Locust 

 Administration, 



The locust season under review Las been the worst that South Africa 

 has experienced for over twenty years. A heavy infestation was antici- 

 pated, but not nearly of such intensity and so widespread as was the 

 case. 



Reference to the accompanying' map will show that the whole of 

 the Karroo, Bushnianland, the north-western districts of the Cape Pro- 

 vince, the western half of the Orange Free State, and the western 

 districts of the Transvaal were infested with voetgangers. The 

 campaign commenced during the last Aveek of September, 1921, and 

 ended in the middle of May, 1922. The first voetgangers were 

 hatched out in Prince Albert District, and the last in Ma f eking and 

 Vryburg Districts. During the season 58 magisterial districts were 

 infested with voetgangers ; 118,662 swarms were destroyed under 

 supervision, and 92,675 gallons of concentrated, that is, approximately 

 5,OUU.0UU gallons of diluted, poison were issued. 



Owing to the fact that in a large number of the infested districts 

 only intermittent light showers fell, the campaign was extended over 

 a longer period than it would have been had good heavy rains fallen 

 and all the eggs liatched out at one time. 



Having two campaigns naturally increased the expenditure and 

 rendered the work of the locust officers far more difficult, in that it 

 required constant pressure on their part to keep the farmers enthusi- 

 astic over the destruction of the locusts. Had heavy rains fallen the 

 voetgangers would have all hatched out at one titne, the campaign 

 would have been over much sooner, and even better work than lias 

 been done would have been accomplished. A peculiarity that occurred 

 in one or two districts was that the bottom layer of eggs hatched out 

 before any rain fell. This is accounted for by the fact that the eggs 

 were laid in damp ground. The bottom layers hatched out as soon 

 as the weather became warm, but the top layer only hatched out when 

 the rain fell and they received the necessary moisture. 



Explanation of Reappearance of Locusts in such 

 VAST numbers. 



The theory that outbreaks of locusts follow a severe drought has 

 been amply proved this season, for the districts in which the infesta- 

 tion was most intense were those that suffered severely from the 

 drought of 1919. When this drought broke, breeding up commenced, 

 but, as locusts had not been prevalent for some time, the farmers had 

 become lulled into a sense of security and did not take notice of the 

 stray and scattered locusts that appeared in 1919-20. So greatly 

 and quickly, however, do the locusts multiply, if unmolested (experi- 

 ments have proved that one female can lay between 300 and 400 eggs 

 in her brief lifetime), that in 1920-21 the scattered locusts formed 

 into swarms, and as many as 27,000 swarms were destroyed. The 

 reason for the abnormal outbreak during the past season is difficult 



