42 PRESIDENTIAL ADDRESS SECTION C. 



excessive in insects. Locusts are not specially fecund, yet in 

 one season, in the absence of checks, the Red Locust would 

 multiply over fifty-fold and the Brown Locust a thousand-fold. 

 The predatory and parasitic cliecks on most insects speedily re- 

 assert themselves and soon again restore the normal balance ; 

 but, by forming large swarms and migrating, locusts may be 

 thought to escape their checks to a considerable degree, and 

 thus be in a position to continue to multiply abnormally much 

 longer than the plant-feeders in general. The past summer 

 furnished a large part of the Union with an illustration of this 

 effect on many insects of a rainy season following a series of 

 relatively dry ones. Grasshoppers, butterflies, moths, and 

 plant bugs were extraordinarily numerous. For a while it 

 seemed as if, before the growing season ended, the hordes of 

 caterpillars would have eaten off every green leaf : but, long 

 before the season closed, ordinary conditions were to a large 

 extent restored, parasites and disease suppressing most of the 

 ravaging insects in a surprisingly short time. 



Whatever the immediate cause or causes of excessive increase 

 in locusts, and the conse(|uent formation of great swarms, 

 I do not think it can be doubted that the fundamental cause is 

 a cyclical climatic change in the region where the insects have 

 their permanent home. Hence I think we must look to the 

 meteorologist and other students of climate for some of the 

 information necessary to unravel the mysteries surrounding 

 these insects. From my superficial study of the general subject, 

 I have become impressed with the fact that locust visitations 

 in South Africa have closely followed long droughts that have 

 been thoroughly broken up by widespread general rains. Moffat 

 (Missioiiarx Labours) mentions that the vast swarms he saw at 

 Kuruman in 1826 came after a long and serious drought had 

 given place to a good season. The years 185S to 1862 are 

 recorded to have been very dry years, 1862 being still remem- 

 bered as one in which rivers ceased to flow that had never been 

 known to fail before ; and, quick on the return of good seasons, 

 followed the locust cycle that reached its greatest -height in 1864, 

 but continued to 1876. Then 1883 seems to have ushered in 

 another succession of bad seasons, broken late in 1889, and 

 followed by a locust visitation that, first recorded in February. 

 1890, at Beaufort West, spread over the Transvaal and Orange 

 Free State and much of the Cape Province in 1891, and reached 

 its climax in 1893. A severe recrudescence of the plague 

 followed when what w'as called a " great drought "' in Bechuana- 

 land, Transvaal, and Orange Free State ( see Cape Agricultural 

 Journal. 23, 512^) broke up with splendid rains late in 

 1903. This secondary visitation culminated in i(p7. and 

 settled parts of the Union were practically free from the pest 

 m the following year. But 1908 was a dry year in the southern 

 Kalahari, and after phenomenal rains there earlv in 1909, 

 swarms again swept down over a large area of the Orange Free 



