166 



Principles of Plant Culture. 



ner in which it works its injury, as upon this will depend 

 the preventive measures to be used. 



306. Injurious Insects are referable to Two Classes, viz., 

 eating insects, i. e., those feeding directly upon the plant 

 tissues, as the potato beetle, the apple-tree 

 borers,* the plum curculio; f and the suck- 

 ing insects, i. e., those feeding only upon the 

 juices of the plant, as plant lice, the squash- 

 bug, % and the oyster-shell bark-louse. 



307. The Eating Insects may be subdi- 

 vided into leaf-eaters, those that devour the 

 foliage; root-eaters, those that devour the 

 roots 5 and bur rowers, those that har- 

 bor within some part of the 

 plant by eating a passage for 

 their bodies. 



308. The Leaf-Eaters include 

 numerous species. They are 

 readily recognized by the fact 

 that the leaves, on which they 

 a feed, disappear 



more or less rap- 

 idly. They may 

 generally be d e- 

 stroyed by apply- 

 ing a poison to the 

 foliage, for which 

 purpose the arsen- 



PiG.71. Steam spraying outfit, manufactured leal Compounds are 

 by the Shipman Engine Co., Rochester, N. Y. well adapted (284). 



In cases where the use of a deadly poison is unsafe, hel- 

 lebore (289) or pyrethrum (290) may be substituted. 



* The round-headed apple-tree borer, Saperda Candida; the flat-headed 

 apple-tree borer, Chrysobothris femorata. f Conotrachelus nenuphar. 



I Anasa tristis. $ Mytilaspis pomorum. 



