FOREST PROTECTION 87 



though they had been sprinkled with snow. After mid- 

 summer, wings are acquired, and the insjects spread from larch 

 to larch and to the spruce. 



In the case of both Spruce and Larch the attack is worst 

 upon sickly trees, and those at the margins of woods. Where 

 the pest on the Larch is very persistent and the damage severe, 

 it is usually found that the situation is also in other ways 

 unsuitable for the growth of that species. 



As prevention, the Larch should not be grown in pure 

 woods nor in close, " muggy " situations, nor on cold, damp 

 soil. The crowns of the trees should not be much restricted, 

 but be given liberty of space and air. 



Young Larches in the nursery may be sprayed, by means 

 of one of the " Knapsack " sprayers, with paraffin emulsion. 

 Against the aphis on Spruce, nothing can be done in the 

 forest except the removal of weak trees. 



Useful Forest Insects 



Insects are not all harmful, on the contrary, quite a number 

 are most useful, performing direct service for man. But it is 

 the indirectly beneficial carnivorous insects that more especi- 

 ally interest the forester. These consist of predatory and 

 parasitic species living upon injurious forms. They have 

 repeatedly put an end to insect scourges that had got beyond 

 human control. 



To the predatory class belong several beetles, amongst 

 them Calosoma sycophants, Calosoma inquisitor, lady - birds 

 (Cocdnellidce\ and tiger-beetles (Cmndelidte). As parasites, 

 the Ichneumon flies render good service : Microgaster nemorum 

 and Microgaster glomeratus lay their eggs in the body of the 

 Pine Moth larva. Anomalon circumflexum is another and 

 frequently occurring ichneumon, whose habits are altogether 

 beneficial through the killing of destructive caterpillars, and 

 of the true flies (Diptera), the genus Tachina supplies several 

 species which are very active in this direction. 



