64 PRACTICAL TREE REPAIR 



amount of cambium it destroys. The only 

 measure which can be taken against it is the de- 

 struction of infested trees. The main reason for 

 describing it here is to prevent confusion of this 

 insect with a beneficial parasite upon it which is 

 often blamed for the work of the tremex. The 

 parasite is an ichneumon fly, Thalessa lunator, 

 which slightly resembles the tremex in appearance, 

 though the ovipositor of the female, instead of 

 being half an inch, is three or four inches long. 

 The male has a slender abdomen, and both have 

 dark spots on the first pair of wings. The Tha- 

 lessa deposits its egg in the burrow of the tremex, 

 and its larva causes the death of the tremex larva. 



Such are the principal insect enemies of trees 

 with which the tree repairer is likely to have to 

 deal. 



All these pests must be fought relentlessly, and 

 it is the duty of the local government, and at times 

 of the State and National Governments, to lead 

 in the fight. The best line of campaign is preven- 

 tion, and effective preventive measures must 

 usually be undertaken on a larger scale than is 

 possible to a;iy but the largest private owners. 

 Insomuch as most of these insects prefer, and 

 increase rapidly upon, weak and dying trees, the 

 authorities should see to it, in so far as they have 

 power, that dying trees are removed and burned, 

 and that weak ones are pruned and fertilized into 



