THE LARGE LARCH SAWFLY. 153 
means of reducing the numbers of larve on trees too tall to be 
sprayed. A draw-knife is used to smoothe the rough bark on a 
belt about 15 in. wide round the trunk of the tree at about 
breast-height. Archangel or Stockholm tar, slightly heated, is 
applied to the surface. The tarring requires repeating about 
once a fortnight whilst the attack lasts, in order to keep a moist 
surface. Bands of straw covered with tar are also fastened 
round the trees. By either method the larve perish on the pre- 
pared surface in their attempt to reach the higher portion of 
the tree. Small trees can be shaken by hand before being 
tarred ; the larve, if they have got past the earlier stages, will 
then drop off like rain. Shaking has no effect on the smaller 
larve. Trees too large to be shaken by hand are jarred by striking 
them with a wooden mallet provided with a piece of felt or sack- 
ing on the striking face, in order to prevent damage to the bark. 
Jarring should be repeated at least once a week. Unfortunately 
a great number of caterpillars never fall to the ground, and are 
therefore unaffected by the tar-banding. 
Though much good may be done by these methods, it. appears 
to me that the means which holds out the best prospect of per- 
manently reducing the numbers of N. erichsoni is by way of 
encouraging the natural enemies of the pest. Fortunately there 
is an ichneumon which is parasitic on the larve of the Large 
Larch Sawfly; this is Mesoleius aulicus. It has been proposed 
by the Board of Agriculture to breed out cocoons from woods 
where these ichneumons have been observed, with a view to 
determining the percentage of larve parasitised, and if a satis- 
factory result is obtained, to distribute numbers of the cocoons 
among woods where the attack is just beginning. By hatching 
the cocoons under a net the sawfly can be retained and killed, 
and the parasites allowed to go. It is hoped that in this way the 
parasites will obtain a much wider distribution than by natural 
means, and that the spread of the sawfly will be checked and its 
attacks minimised. It is noteworthy that the number of pup 
affected with the ichneumon at Thirlmere rose from 15 per cent. 
in 1909 to about 62 per cent. in 1910. Some collected for and 
examined by Hewitt in the spring of 1911 only showed 18 per 
cent. parasitised. Others from near Crummock Water had as 
few as 6 per cent. parasitised. 
Zool. 4th ser. vol. XVI., April, 1912. N 
