H. M. Deakin 83 



worse than the rest of the oaks in the park. Had the attack been as 

 bad as last year's, doubtless a contrast would have been apparent 

 between those trees which were thoroughly sprayed and trees outside 

 the plantation which were not touched. The growth of the leaves was 

 very rapid during the favourable weather which followed the time of 

 the spra3'iug, and the coating of spray, observable for some days and 

 quite unaffected by exposure and rain, finally disappeared owing to the 

 expansion of the leaf. Rain fell while the trees were being sprayed 

 and to some extent this must have affected the deposition of the spray. 

 Caterpillars fed on sprayed foliage either died at once or became starved 

 and finally perished, so that no doubt remains as to the efl&cacy of the 

 poison. 



The question of the falhng off in the severity of the attack this year 

 is an interesting one. The possibility of birds influencing this, has 

 already been touched upon. 



It is possible that last season the parasitic enemies of the chief 

 caterpillar pests were very numerous, thus lessening the numbers this 

 year. The caterpillars appeared however to be numerous enough, 

 especially those of T. viridana. It may be that the dry sunny weather 

 of May and June this year (1913) so favoured the rapid growth of the 

 oak foliage that this easily kept ahead of the attack of the caterpillars, 

 the growth of foliage being greatest when the caterpillars were most 

 numerous and dangerous. 



It can readily be understood that if the growth of the foUage is 

 delayed by unfavourable weather the caterpillars will gain the upper 

 hand and the foliage already present will disappear and the tree will 

 assume the bare appearance typical of years of bad attack. The weather 

 last year (1912) I believe was favourable for the trees till the beginning 

 of June when the weather became colder and damper. If the cater- 

 pillars were still active at this time, they may have caused the stripping 

 of the trees, on the cessation of the fine weather. 



I should like to take this opportunity of thanking Professor Lefroy 

 for the advice and assistance which he gave me during this investiga- 

 tion, and Mr Pullman, the park superintendent, for his advice about 

 the trees and caterpillars. 



[Mr Deakin's observations were put an end to by his appointment 

 as assistant to the Government entomologist, British East Africa. 

 The almost entire absence of any visible effects of caterpillar attack 

 anywhere in Richmond Park in 1913 destroyed the value of our experi- 

 ment as no plantation in the park was affected. But it showed that 



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