77 



THE CATERPILLARS ATTACKING THE OAKS OF 

 RICHMOND PARK, WITH AN ACCOUNT OF 

 AN EXPERIMENTAL SPRAYING WITH LEAD 

 CHROMATE. 



By R. H. DBAKIN. 



The oak trees of Richmond Park have suffered very extensively 

 of late years from the attacks of caterpillars. 



I have not personally seen the damage done in previous years, but 

 from all accounts the trees last year (1912), as also the year before, were 

 almost stripped of foliage, presenting as a result the appearance of dead 

 trees. A secondary growth of foliage then occurs. The period of maxi- 

 mum damage is said to have occurred in June, the time doubtless 

 varying with the weather conditions in the spring. Impressed by the 

 serious nature of the damage, the authorities at Kew Gardens com- 

 municated with the entomological department of the Royal College 

 of Science, and Professor Lefroy, under whose guidance I have been 

 working, took the matter up. 



It was decided that one section of the oaks in the park should be 

 kept under observation and sprayed and for this purpose Ham Cross 

 Plantation, consisting of some 400 large oak trees planted in 1825, was 

 chosen. 



This plantation, presenting a very compact area of trees, has been 

 very severely attacked in previous years. 



I first visited the plantation in the third week of April. Some half 

 dozen trees were already breaking into leaf and on these minute cater- 

 pillars were observable. 



From this time onwards the number of caterpillars and the accom- 

 panying damage to the leaves increased rapidly, and it became possible 

 to collect the different forms for the purpose of breeding out the moths. 



The two commonest caterpillars were soon seen to be those of Tortnx 

 viridana, the leaf-roller moth, and Cheimatobia hrumata, the winter 



