THE IIYLOTOMA. 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 larvse 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 larvse. The long winter passes and the early 

 spring finds the larvse 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 



