544 



ap]3earance of L. pardalina on both these occasions has followed the 

 break-up of a protracted drought, and it seems evident that isolated 

 locusts or unobserved clusters had been continuously present generation 

 after generation and were suddenly able to multiply enormously. It 

 is considered that living eggs may accumulate in the soil during a 

 succession of dry years, and that a protracted drought greatly favours 

 the locusts by relieving them of natural enemies that are relatively 

 slow to respond to the opportmiities for increase afiorded by a good 

 season foUowng very dry ones. In the case of the 1915 outbreak 

 similar conditions seem to have occurred. Swarms of locusts invaded 

 the district in March and April 1909 and deposited eggs. In the follow- 

 ing spring, the hoppers hatching from these eggs were combated 

 energetically ; the few winged forms that developed were largely 

 preyed upon by birds and were thought to have been exterminated 

 before eggs could have been deposited. From April 1909 until Novem- 

 ber 1914, drought conditions prevailed throughout the district ; after 

 the latter date rain set in, causing a luxuriant growth of grass, and 

 plant-feeding insects, including grasshoj3pers, became increasingly 

 abundant, true locusts appearing about February 1915. Necessary 

 materials for control, including pumps and poisons, were at once 

 distributed and efforts were made to control the hoppers of the second 

 generation. Owing, however, to the absence of swarm formation 

 and the difficulty of locating the locusts in the tall grass, this work 

 was not very successful, and later in the season isolated winged locusts 

 were found occurring over an enormous area, w^hile many small swarms 

 hovered about. Many initial measures were taken to acquaint the 

 public with the danger that threatened and wth their obligations in 

 dealing with the pest. 



Hatching of the eggs began in September and was very protracted, 

 owing to the rains not reaching all the eggs at once, thus rendering 

 control measures more difficult. The outbreak was not uniform, but 

 was much more intense in a number of districts than had been antici- 

 pated. A table is given detailing the locust destruction in various 

 centres during September-December 1915. 



The locusts of the first generation that escaped destruction began 

 to reach the winged state during the first week of December and 

 probably were all on the wing by the 24th, w^hen the last known 

 swarms of hoppers w^ere dealt with. The number of wnnged forms 

 succeeding the hoppers seemed small, about 75 swarms being reported, 

 but small lots and isolated individuals were found to be scattered over 

 a large area. Oviposition by the new generation began to be observed 

 in early January, and before the end of the month new hatchings 

 were reported. Until the end of April swarms of hoppers appeared 

 sporadically over the infested area, extending north-west and south- 

 west over new country. These new locusts were in part the progeny 

 of the earlier ones, but in part from eggs that had certainly been in 

 the ground for six months or longer. The swarms were much less 

 numerous than in the earlier outbreak and few were really large, but 

 they were spread over such an immense area and appeared so irregu- 

 larly that their suppression entailed considerable difficulty and expense. 

 Methodical farm to farm inspection for locusts over such a vast area, 

 where the average farm is upwards of 10,000 acres in extent and 

 sometimes more than five times as large, is quite impracticable'in the 



