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



Adirondack^ by eating away the leaves. Even the small and 

 vigorous larches do not escape." 1 Another report on the 

 saw-fly states that " During several extensive outbreaks since 

 1880 it has killed 50 per cent, to 100 per cent, of the mature 

 larch over vast areas in the North-Eastern United States and 

 South-Eastern Canada. It is evident that the amount of 

 merchantable timber which has died as the result of defolia- 

 tion by this insect will aggregate many billions of feet." 2 



The insect is now distributed throughout North and Central 

 Europe, and Siberia, and in North America from Central 

 Michigan to Labrador. 



Life-History. — The life-history of Nematus Erichsoni has 

 been carefully described in previous publications issued by 

 the Board, 3 and there can be little doubt from the description 

 that the species of saw-fly in North America and in Britain 

 is identical. American entomologists believe that it was 

 introduced to North America from Europe. There is no 

 evidence to show how the saw-fly was introduced into 

 Great Britain, and it is quite possible that it has been present 

 for a number of years, but for some cause or another has 

 not until recently materially increased in numbers. Larch 

 plantations are, indeed, said to have been defoliated in the 

 Lake District by a caterpillar about the year 1868. The 

 caterpillar has been stated to be identical with the larvae of 

 Nematus Erichsoni, but there are no records to prove that this 

 was the case. 



A few points in the life-history of the saw-fly which were 

 previously not quite clear have been elucidated. It has been 

 found that the caterpillars, when full fed, simply drop from the 

 trees to the ground and there proceed to spin their cocoons; 

 the cocoons were almost invariably found between the moss 

 or litter and the soil, so that if the former be rolled back 

 the cocoons are practically all exposed. Naturally the 

 cocoons will be most abundant near the base of the tree, but 

 they are also found scattered irregularly over the whole area 

 covered by the crown. 



1 A Primer of Forestry, U.S. Dept. of Agric. Bull. 24, Div. of Forestry. 



2 " Insect Depredation in N. American Forests," U.S. Dept. of Agric. Bureau of 

 Entomology, Bull. 58, part 5, p. 60. 



z /ournal of the Board of Agriculture, Oct. 1906, and Dec. 1908; and 

 Leaflet No. 186. 



