THE LARGE LARCH SAW-FLY. 1 89 



Other Saw-flies : — Nematus erichsoni. 



The Nematus laricis, or Has a black head, and body 



small larch saw-fly caterpillar, is greyish green, 



has a brown head, is grass Feeds and grows till the 



green or greenish brown in end of August, 

 colour. It is full - grown in 

 July. 



The larvae leave the trees when full-fed, and spin cocoons in 

 which they live till the spring when they pupate. The cocoons 

 may be looked for under the affected tree not only near the 

 trunk but also over the whole surface covered by the crown of 

 the tree. The cocoons are found in the soil under the moss and 

 litter that usually cover the ground under larch trees, and this 

 must be turned back when the cocoons are being hunted for. 

 These are dark brown and cylindrical with rounded ends, and 

 about half an inch long. 



The adult saw-fly on emerging from the cocoon, after the 

 pupal stage is over, is in general appearance black, with glassy 

 wings. The female flies at once to the lower branches of the 

 tree, to lay her eggs, but apparently much of the life of the 

 insect in this stage is spent on the wing and round the upper 

 branches. It can therefore easily be overlooked, and is difficult 

 to identify at any distance. The large larch saw-fly is nearly 

 twice as long as the small larch saw-fly and can be distinguished 

 from the latter, which is quite black, by the red segments of the 

 abdomen. 



Larch plantations that are suspected of having been attacked 

 should also be examined, with the object of discovering traces 

 of infestation. This work may be carried out from the middle 

 of June to the end of November. The symptoms to be looked 

 for are as follows : — In June and July a search should be made 

 on the terminal shoots of the branches for signs of eggs, which are 

 laid alternately in two rows. The number is usually about 

 twenty, but as many as forty have been found. The easiest 

 sign, however, to notice is the distortion of the current year's 

 shoots, which often curl up when eggs have been laid in them. 

 A closer examination will generally reveal the incisions made by 

 the saw-fly's ovipositor on the concave side of the curled shoot. 

 The slits where the eggs have been laid resemble small eyes less 

 than y^jj inch in diameter. A little later, in July and August, 



