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ent species of oak. In Fig. 20 (after Corastock) we have an oak leaf represented, covered 

 with blotches. These are of a dull yellowish- white colour, and are caused by the larva of 

 this insect, which lives between the upper and under skins of the leaf and consumes its 

 substance. The young larvae are shown at h, in the figure ; c,f, and g represent the larva 

 in the later periods of its growth; m the chrysalis and a the moth. Although .each insect 

 makes but an insignificant blotch on the leaf, yet they are sometimes found in such 

 countless multitudes that almost every leaf has a colony of them, and this interfei'ence 

 with the vital functions of the tree by the destruction of the foliage often seriously injures 

 it, and sometimes causes its death. 



The White Pine Saw-fly — Lophyrus abbotii. 



Moths and their caterpillars are not the only enemies the tree grower has to contend 

 with ; foes of the most formidable character are found as well among other orders of 



insects. Probably, no insect is more gen- 

 erally destructive to the white pine than 

 the pine saw-fly, belonging to the order 

 Hymenoptera, which is represented in its 

 different stages in Fig. 21 (after Riley), 

 The larvae, shown at 4 in ^^^ figure, are 

 found in colonies, keeping together until 

 full-grown, and after stripping the leaves 

 off one twig or branch they pass on to the 

 adjoining branches, until sometimes one 

 side of a tree, or, if it be of small siz^, the 

 whole tree will be denuded of its foliage 

 and destroyed. They appear from mid- 

 summer until October, are nearly an inch 

 long, of a yellowish-white colour, with 

 three or four longitudinal rows of black 

 spots. When mature they form tough, 

 brown, pod-like cocoons attached to the twigs within which the change to a crysalis takes 

 place, from which, in due time, the perfect fly escapes. 



The Hickory Aphis — Aphis Caryalla. 



This is a small yellow aphis which lives on the under side of the leaves of the 

 hickory. Its antennae are ringed alternately with white and black, the wings are tran- 

 sparent, without spots, and the legs yellowish white. This insect, in common with all 

 other plant lice, lives by suction ; it inserts its beak into the tissues of the leaf and lives 

 upon the sap. 



Having briefly referred to some representative species in each group of these insect 

 enemies to forest culture, we now pass to the consideration of the remedies, natural and 

 artiticial, available for their destruction. 



It is obviously extremely difficult, if not impracticable, to undertake to destroy or 

 control by human agency, insects injurious to forest trees. The area covered by them is 

 so great that the labour and expense connected therewith would be out of all proportion 

 to the good likely to be accomplished. Artificial remedies are applicable only to street 

 trees, small groups on the lawn or ornamental ground, or to plantations of young trees, 

 where the depredators may be easily reached, and since such trees or groups are in most 

 instances esteemed as of great value by the owners, and are objects of constant solicitude, 

 they are worthy of special efforts for their preservation. 



It is difficult to reach insects which make their home either on the surface or in the 

 interior of the roots of trees. Where the presence of such insects are suspected, the sur- 

 face soil should be removed and the superficial roots examined, when if convincing 

 evidence of their presence is found, scalding hot water should be poured upon the roots thus 

 laid partially bare, and the earth replaced. It has also been suggested to apply bisulphide 



Fi-. 21. 



