ON iMETHODS OF PREVENTING INSECT ATTACK 43 



impaired In' the frost. The forests were full of stag-headed trees or poles 

 with their upper parts dead, and the fact that the presence of the insects 

 was not more apparent was simply due to the large number of weakly and 

 d}'ing trees for them to breed in. 



The after-effects of severe frosts in young pole forests will need very 

 careful watching in future, since the crops on the ground are, with better 

 and closer management, yearly becoming more dense, and thus more 

 susceptible to insect attacks. 



3. Methods of Ascertaining the Presence of Insects in the Forests and of 



Preventing' Damage. 



The abundance of particular insect pests in an area of forest may be 

 ascertained in various ways, depending to a great extent on the life history 

 of the individual pest. For instance, defoliating caterpillars when in 

 abundance soon make their presence evident by stripping the leaves from 

 the trees. A knowledge of the full life history and appearance of these 

 insects will, however, enable the forester to be forearmed against this form 

 of attack, for before the larvae appear in swarms sufficient to completely 

 defoliate the trees, the moths must have previously been swarming on the 

 wing in the forest, laying the eggs from which the larvae hatched out. 

 Therefore, if you have the knowledge which will enable you to recognize the 

 moth you will have been forearmed against a probable serious attack of the 

 caterpillars. Reports have often been forwarded to me that in such a month 

 small moths have been seen in great numbers iiying about the trees. A 

 few weeks later these trees have been stripped bare of all foliage. The 

 life histories of the insects being unknown, however, the knowledge which 

 would ha^'e connected the first appearance of the moths with a probable 

 subsequent severe defoliating attack was absent. 



The seed of trees is also subject to attack by caterpillars, the sal by the 

 larvae of Coccotrypes sp. (p. 543) and the caterpillars of species of Conogethes, 

 Laspeyresia, Cacoccia, etc., and the deodar, silver fir, spruce, and blue pine 

 by caterpillars of the moths Phycita ahietclla and Euzophcra cedyella. If 

 the small moths of these species are ver\' abundant in the sal forests just 

 before the rains, it may be taken as almost certain that the seed crop 

 the follow^ing year will be severely attacked, and will be practically a 

 failure. Similarh', in the case of the conifers, if the moths of the two 

 species above mentioned are numerous in the forests in September and 

 October, the probabilities are that the cones of the following season 

 will be riddled by caterpillars, and the production of seed be very 

 scanty or nil. These inferences are not of course certainties, since a long, 

 cold, wet spring in either case may result in many of the young caterpillars 

 hatching out of the eggs laid by the moths on the twigs of the trees 

 being killed before they have got into the interior of the seed or down 

 into the cone. 



