348 PROTECTION AGAINST INSECTS. 



accompanies the larch, and has recently become abundant in 

 Switzerland, where the larch is indigenous. It sometimes 

 appears in myriads, 50,000 larvae having been found on a plant 

 only 12 years old in Schlucken, 1895. 



Independently of its large numbers and wide dissemination, 

 its great hurtfulness results from its eating the needles twice 

 during the same year, and appearing year after year in the 

 same localities. As the larch disease almost always accom- 

 panies this insect, the latter probably renders the tree 

 susceptible to this highly destructive fungus. The loss of 

 increment is considerable, owing to the destruction of needles 

 in the spring, so that trees are often so weakened by repeated 

 attacks that they die. 



d. Protective Rules. 



Choice of suitable localities for larch, and planting it widely 

 apart. 



Mixture of larch with beech, spruce, silver-fir, etc. 



Early thinning, and removal of the thinned material, at the 

 latest, by the end of March. 



Protection of titmice and other small birds. 



e. Remedial Measures. 



Pruning the lower branches of larch trees, on which the 

 insect usually appears. 



Kemoval of badly attacked and weakened trees from the 

 middle of June till the end of August. The caterpillars in the 

 needles of these trees will not then become fully developed. 



The little cases may be picked off the trees, and destroyed 

 during the winter and spring, but this plan can be followed in 

 forest nurseries only. 



