130 



AN ECONOMIC ENTOMOLOGY. 



been introduced, and, after a long series of experiments with 

 insecticides, none of which proved satisfactory, resort was finally 

 had to American stocks upon which the foreign varieties were 

 grafted. This has proved effectual to an extent ; but it seems 

 that, in the course of time, the period varying somewhat, even 



American stocks lose 

 their exemption in 

 Europe and become 

 gradually subject to 

 injury from the Phyl- 

 loxera attacks. 



We have a number 

 of species of this same 

 genus infesting a great 

 variety of plants not 

 of economic interest. 

 Perhaps the most com- 

 mon is that which 

 forms large, blister- 

 like galls on hickory 

 leaves, so prominent 

 as to attract attention 

 from even the most 

 casual observer. If one of these galls be cut open, the inside 

 will be found lined with numerous minute, yellow insects, with 

 dusky wings which lie folded flat over the back, and in this par- 

 ticular the Phylloxera differs from the typical aphids, which have 

 the wings vertical when at rest. 



The subject of dealing with underground pests, or plant-Hce 

 which feed upon roots, is one of importance, upon which the 

 last word has not yet been said. As against the Phylloxera., 

 bisulphide of carbon has proved useful, injected by means of a 

 proper instrument into the ground at about the level of the roots 

 and allowed to permeate the soil. The fumes are deadly to 

 insects, and where they reach them in any but the egg stage, 

 kill. The Phylloxera does not require attention in our country 

 at the present time, and no large space need be given the subject 

 of remedies against it. The matter is different when we consider 

 the species which infest other cultivated plants ; whether Rhizo- 



FiG. 95. 



Galls of Phylloxera on grape-leaf. 



