75 



of preserving, if possible, the foliage of the trees from any injury 

 whatever. A much weaker mixture would be almost, if not quite, as 

 satisfactory'. 



Dr. Lintner said he had found 3 pounds of arsenate of lead in 150 

 gallons of water in his experiments to be about the equivalent of 1 

 l)ound Paris green in the same amount of water. 



Mr. Webster read a paper on the probable origin of the .uenus Dia- 

 brotica. This paper, being somewhat technical in character, has been 

 withdrawn by Mr. Webster for publication elsewhere. 



The f(jllowing paper by Mr. Hopkins was read, in his absence, by Mr. 

 Southwick : 



ON THE STUDY OF FOREST-TREE INSECTS. 



By A. D. Hopkins. Morgantown. W. Va. 



The study of the insects aftecting forest growth, from an economic 

 standpoint, is in many respects a unique branch of economic ento- 

 mology, Avhich should in our opinion be designated bj^ the term '^ for- 

 estry entomology."' 



The importance of advancement of knowledge in this particular 

 branch of science may be inferred from some references to the char- 

 acter of insect injuries to forest growth; to estimates of the amount of 

 damage and the annual pecuniary loss occasioned by such injuries; to 

 the limited knowledge of this class of insects, and to the possibilities 

 of preventing a large per cent of the loss by the adoption of simple, 

 practical methods of combating the pests. 



CHAKACTEK OF I^^TT'KIES. 



The injuries to forest growth maybe separated into two classes, those 

 affecting the living plants and those affecting the dead or dying plants. 

 Of the former we have injuries to the foliage bj' leaf-eating, leaf-mining, 

 sap-sucking, and gall-making insects: to the twigs and branches by sap- 

 sucking, twig-mming, bark- and wood-boring insects; to the trunk b}' 

 bark- and v/ood-boring, and to the roots by wood-boring, bark-boring, 

 and sap-sucking species; the effect of the injuries thus caused upon 

 the living plant being either destructive or detrimental to its growth 

 or usefulness. 



1'he injuries of a destructive character are those caused by insects 

 which occur in sufficient numbers and make their attack in such a 

 manner as to destro}' or weaken the vitality of the tree sufficient to be 

 the primary cause of its death. 



The injuries of a detrimental character are those which are detri- 

 mental to the health, perfect growth, or future usefulness of the tree or 

 its product, but does not cause its death. 



Of the injuries affecting the dying and dead trees we lind, as among 

 those affecting the living, some which are of a destructive character, 



