42 >1K. C. B. HAKDENBERG 



The Wattle Plantation — The effects of tlie 



Present methods of Wattle Growing on the 



Insect Problem, 



By C. B. Hardenberg^ M.A. 



Introductory. 



The investigation of the insects injurious to the Black 

 Wattle, Acacia mellissima, Wild., is a very large subject 

 and even a mere enumeration and short discussion of the^ 

 various species involved would carry the length of thia 

 paper far beyond reasonable limits. I will therefore con- 

 fine myself to a discussion of the influence of the existence^ 

 of the large wattle ;.lantations on the insect fauna and 

 how the present methods of wattle growing affect the- 

 insect problem. 



Effect of the establishment op 



WATTI,E plantations ON THE InSECT FAUNA. 



Before the introduction of tlie Black Wattle there 

 existed large areas of thorn bush veld, dotted over with 

 various species of Acacias and Mimosas, sustaining a 

 host of insects, uativo to the country, but which, partly 

 on account of the comparative si^arsity of the trees and 

 their scattered posilion, could not increase to such an 

 extent as to (hreaten entire areas Avith extinction. A 

 balance between injurious insects on the one side, and 

 parasites and limits of food supply on the other side, had 

 been established and was apparently being maintained 

 with slight fluctuations. Even now this is the case, for 

 notwithstanding the enormous numerical increases of the 

 various insects, we find that the native thornbush is not 

 seriously afl'ected : a wholesale infestation in one season 

 being speedily reduced to normal conditions. 



