99Q Distribution of the Large Larch Saw-fly. [march, 



comparatively safe from the weather. On hatching, the 

 female flies at once to the lower branches and lays its eggs 

 (apparently without the intervention of the male), and the 

 caterpillars, when full fed, do not descend the trunk but fall 

 direct to the ground. Artificial remedies, such as tar-banding, 

 are therefore of little use. 



2. The saw-fly is very mobile, and can therefore spread 

 rapidly. 



3. Under the sylvicultural conditions which usually obtain 

 in British larch woods the ground is covered with grass and 

 moss, which renders the collection of cocoons difficult. For 

 this reason there must always remain a number of woods in 

 a district which it would be impossible to treat economically, 

 and such would serve as centres of re-infestation. 



4. The fact that tall trees are attacked equally with young 

 ones. 



5. The apathy which many owners show towards the 

 welfare of their plantations. 



At the Manchester Waterworks plantations at Thirlmere 

 two remedies have been tried. The younger trees have been 

 sprayed with a mixture of arsenite of copper, 1 lb., flour, 

 1 lb., and water, 128 gallons. A knapsack sprayer was used, 

 and it was found that, by a suitable arrangement of tubes, 

 trees from 15 to 20 ft. high could be conveniently sprayed. The 

 spraying was undertaken towards the end of July, principally 

 in two plantations eight years of age and 6 to 8 ft. high; 

 the effect was greatly to reduce the number of caterpillars, 

 though in the autumn there were still a few present. 



The total area sprayed was about 40 acres, and the stock 

 practically pure larch. The cost is given by Mr. Edwards, 

 the forester, as follows : — ■ 



Cost of labour for spraying ... £10 19 2 

 ,, insecticide ... ... ... 1 3 6 



Total ... £12 2 8 



This works out at an average cost of about 6s. id. per acre. 



In the older woods tar-banding was tried. It w 7 as noticed 

 that during high winds and after heavy rains a number of 

 caterpillars were to be found on the ground, and that, if left 

 alone, they ultimately reached the crown of the tree again. 

 To prevent this, the rough bark was removed from some of 



