IHE -.VATr/.E PLANTATION ili 



With the advent of the large wattle plantations this 

 kalance of nature was snddenh' disturbed. Thousands of 

 acres of native thornbush and other vegetation were being 

 destroyed and replaced by the black wattle, a congener 

 of the majority of the native trees, which originally 

 formed a breeding place for many of these insects. The 

 change from the old to the new food plant therefore was 

 quickly made and on their new feeding ground they 

 found conditions so much more genial that their increase 

 was extremely rapid. The conditions which had 

 previously prevented their breeding uninterruptedly had 

 been removed, in so far that now there was an unlimited 

 food supply with a greater protection against parasites 

 and other natural enemies, these being the main causes 

 for the phenomenal increase of the wattle insects 'luring 

 the last decade. 



As proof of my contention I give here a comparison 

 between the condition of the Wattle Bagworm, 

 Acanthossyche junodi, Heyl., found in the thornveld and 

 the same species in the Wattle plantation. The former 

 was taken under its most favourable conditions, ramely 

 from a tree which had been infested for the first time, 

 (no old bags of previous seasons were found on the tree), 

 the latter under the most unfavourable conditions, i.e. 

 from a plantation which had suffered from bagworm 

 infestation for four successive seasons. For reasons 

 which are not within the scope of this article, the con- 

 ditions become more and more unfavourable for the bag- 

 worm with each infestation of the same block. As a 

 third example I give the conditions of this same insect as 

 found in a plantation of young trees, infested for the 

 first time. 



Average size of bag : — 



(A), male 30 m.m., female 40 m.m. y^^\ P7>\ 



(B). male 47 m.m., female 54 m.m. /~v^ 6^^ ^'o -VX 



(C). Practicallv the same as B. /^ ~ ^*^, >\, ^ 



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