igo8.] 



Large Larch Saw- Fly. 



653 



Dodd plantation on the south-east side of Bassenthwaite Lake, 

 which belongs to Miss Spedding, and which I visited in July, 

 about 200 acres are attacked, and the trees were almost entirely 

 defoliated at the time of my visit. The presence of the larvae, 

 I was informed by Miss Spedding 's head woodman, has been 

 visible for about six years, but he had never seen anything 

 similar to it either in the Dodd or in the neighbouring planta- 

 tions during the sixty years he had lived in the district. The 

 result of this prolonged attack is that many hundreds of the 

 trees have already been killed and many are dying ; of the trees 

 dead and dying 3,000 have been cut down and, I am informed,, 

 there are twice as many still to be felled. 



It is not difficult for the biologist to understand how the 

 death of these trees has been caused by the ravages of the 

 larvae. Like most rather closely planted fell-side larches they 

 have merely a crown of green leaves from which to obtain their 

 organic food ; if this small supply is repeatedly cut off, although 

 possibly for only half its annual life, the tree cannot procure 

 even a minimum amount of food. The result, therefore, of 

 the repeated diminution of the annual store of food over a 

 series of years is, as one would expect, fatal. The vitality of the 

 tree is also affected in another manner. As a result of the 

 defoliation, which is often complete by the beginning of August, 

 the trees respond by putting forth a second crop of green 

 leaves, and the defoliated plantations have a green appearance 

 when all the unattacked larches have lost their leaves. This 

 w 11 not only weaken the already diminished vitality by drawing 

 on the small amount of the stored food of the tree, but further 

 injury may result through the destruction by frost of the second 

 crop of leaves. 



Distribution of Nematus erichsonii in the Lake District. — 

 A fairly complete inspection of the district was made in August, 

 1908, with a view to ascertaining the extent and intensity of the 

 attack, but as it was not possible to visit the whole of Cumber- 

 land and Westmorland the absence of a plantation from this 

 list does not necessarily indicate the absence of the saw-fly from 

 that district. I believe, however, from visits that I have made 

 to neighbouring localities, that the attack is at present confined 

 to the Lake District. The insect was found in the following 

 localities : — 



