THE HYLOTOMA. 
1 73 
and descend to the ground and hide themselves in the soil at 
a slight depth. Others do not leave the stem of their favourite 
tree, and not a few stop upon walls or upon the trunks of trees. 
Wherever they may hide or stop they form an oval-shaped 
cocoon, which is composed of silk joined together by a very 
glutinous secretion, but it never contains grains of sand or of 
earth. 
The cocoons of the rose saw-fly are of an earthy yellow colour, 
and their singular construction was noticed in the last century 
by Reaumur. On the outside there is an elastic tissue which is 
able to resist very considerable shocks and knocks, and the 
microscope shows that it is made up of fibres arranged like the 
network of a racket mace. This is the first envelope, and the 
cocoon beneath it is made up of a soft, close, and flexible sub- 
stance which is not adherent to it. 
When the second metamorphosis is complete, and the Hylotoma 
has changed its pupa skin within the cocoon, it gnaws the soft 
layers with its mandibles, and cuts the stout outside threads with 
them, and escapes. 
The second generation of the rose saw-flies appears towards 
the end of July or the beginning of August. They soon lay, 
and the larvae may be seen upon the roses during the whole 
of the autumn. As soon as the temperature of the season 
begins to decline, and before the fine days are all gone, the 
larvae descend to the earth and establish themselves in their 
cocoons in the soil, and none of them remain on trees or walls. 
They have the instinct to place themselves out of the danger of 
frost and cold, for the winter time is full of peril to them. 
After being snugly housed in their cocoons, where they have 
to remain until the next spring, they become dull and stupid, 
and hybernate as larvae. The long winter passes and the early 
spring finds the larvae in much the same state, but a few fine 
days stimulate their vital processes, and the metamorphosis into 
the pupa condition proceeds. 
The saw-flies are a great pest to horticulturists, and yet a 
slight knowledge of the method of the metamorphosis of the larva 
would enable those generally very self-opinionated persons to save 
many a rose, and prevent much loss to themselves. The habit 
