CONTROL OF WATTLE B.AG^VOEM. 301 



were spread tln'oagh tlie piantations, a condition wliicli mili- 

 tates against the spread of the disease. On the other hand, 

 40 per cent, were destroyed by other diseases in this locality, 

 and this would seem to indicate that the virulence of these 

 diseases is largely dependent on the climatic conditions. At 

 Hilton Eoad mists are almost of daily occurrence during the 

 summer and thunderstorms arc frequent. The excessive 

 humidity during the warm montlis either sets up physiological 

 disturbances which cause the death of the larvae, or else 

 weakens them and renders them peculiarly liable to disease. 



Summary. 

 Out of a total of 59,68T bagw^orms examined, just over 

 1 per cent, were destroyed by birds and rats, 19 per cent, by 

 insect parasites, 16 per cent, by fungous disease, and 17 per 

 cent, by other diseases, making a total of 53 per cent, 

 destroyed. Despite the enormous numbers killed by the above 

 agencies, the figures show that a far greater mortality must 

 take place in tlie younger stages, from September to March. 

 Hardenberg estimates that, of the bagworms which reach 

 sexual maturity, the majority are males, there being an excess 

 of males over females of about 25 per cent. This agrees with 

 my own observations. Therefore, of the 47 per cent, that 

 survive, only 21 per cent, will be females; in other words, out 

 of every hundred bagworms found in the plantations in March 

 only twenty-one females will reach sexual maturity. These 

 females will deposit some forty to fifty thousand eggs, which 

 will hatch in the folloAving* spring-. Assuming no yearly 

 increase on the part of the bagworms, these forty to fifty 

 thousand will be reduced to one hundred by March, that is to 

 say, only one-quarter of 1 per cent, of the larvae hatched 

 survive, the early perils of their life. Even if we assume a 

 lumdrect per cent, yearly increase, only one-half of one per 

 cent, can survive until March. Thus it will be seen that this 

 early mortality, about which very little is known, is by far 

 the most important of the factors in the natural control of 

 the wattle bagnvorm. 



Eeferejn'ces . 

 C. Fuller — 



" Some Common Bagworms and Basketworms."^ — 

 Natal Dept. of Agrio., Bull. XVI., 1909. 

 C. Fuller — 



"The Wattle Bagwovm."— Union of S.A., Dept. of 

 Agric, Bull. 28, 1913. 

 C. B. Hardenberg — 



" Some Insects Injurious to the Black Wattle, Acacia 

 inollissima, Wild." — Union of S.A., Dept. of 

 Agric, Bull. 1, 1918. 

 I. B. Pole Evans — 



" A Fungus Disease of Bagworms in Xatal." — Annales 

 Mycologici, vol. x, No. 3, 1912. 

 E. W. Glaser— 



" Wilt of Gipsy-Moth Caterpillars."— /o?///?. of Agric. 

 Research, vol. iv, ^o. 2, 1915. 



