SOME FACTORS IN THE IS^ATURAL CONTROL 

 THE WATTLE BAG WORM. 



By S. H. Skaife, M.A., M.Sc. 



With Fifteen Te.rt Figures. 



Read July L5, 1920. 



The life-lii.story of the wattle bagworm, Acanthopsyche 

 junodi, Heylaerts, has been studied in detail by Messrs. Fuller 

 and Hardenberg-, and an account of their studies is contained 

 in the iniblications listed at the end of this paper. When 

 I took over the investigations of the wattle insect early in 1919 

 little remained to be learned concerning the life-history of the 

 bagworm, the worst of the pests of the black wattle, hence 

 my attention was turned particularly to the study of the 

 natural enemies of this insect. Among the manuscript notes 

 transferred from New Hanover to the Cedara School of 

 Agriculture were some A'aluable records made by (t. C. Haines, 

 whilst assistant to Hardenberg. Haines had collected large 

 numbers of bagworms at intervals, and had carefully examined 

 each one and recorded its condition at the time of examination. 

 More than thirty-five thousand records had been made in this 

 way, but these had never been .totalled or abstracted. I wrote 

 to Haines, and he generously gave me permission to complete 

 his work and make use of it. During the past eighteen months 

 numbers of bagworms (500 to 1,000) have been collected at 

 intervals in the plantation^ around Pietermarilzburg. These 

 have been examined carefully, and records similar to the above 

 kept of them. Altogether nearly 60,000 bagworms have been 

 examined by Haines and myself, and a broad outline of the 

 results obtained are given in this paper. 



As the bagworm is an indigenous insect, one may reason- 

 ably expect to find that it has many natural enemies, and such 

 is indeed the case. The natural checks include two or three 

 diseases, seven or eight insect parasites, and various pre- 

 daceous enemies. That these enemies forai efficient checks is 

 shown by the fact that the bagworm is effectively controlled by 

 them in normal days, despite its enormous powers of reproduc- 

 tion. According to Hardenberg, the average number of eggs 

 laid per female is 2,300, yet it is only occasionally that severe 

 outbreaks occur, when the plantations are defoliated and 

 serious losses entailed. 



Predaceous Enemies. 



Large numbers of the newly-hatched larvae are destroyed 

 before they have an opportunity of forming their bags. 

 Hardenberg mentions " a small grey spider which enters the 

 bag and destroys its occupants even Ijefore they have left their 



