OF THE FARM AKD GARDEN. 267 



Cresson as a species of Trioxys. Aphides, wherever they 

 occur, are readily destroyed by the use of tobacco, applied 

 as smoke or in infusion as already described. What is 

 known to gardeners as the "Blue Louse" is an aphis 

 which sometimes attacks the roots of verbenas, asters, 

 and other flowers in such numbers as to cause their death 

 before the source of the trouble is suspected. When 

 these underground lice attack the roots, a persistent ap- 

 plication of tobacco-water will save the plants if it is 

 used before the injury has gone too far. 



THE MEALY-BUG. 

 Genus Dactylopius. 



This insect is a common pest of the green-house both 

 in this country and in Europe, and is often injurious to 

 plants in the open air. 

 There are several spe- 

 cies, all of which are 

 more or less covered 

 with a quantity of 

 floury matter secreted 

 through pores scat- 

 tered over the body. 

 They are often very 

 abundant upon almost 



every variety of house-plant and very destructive. They 

 are most frequently found in the crotches of the branches, 

 and close down in the axils of the leaves, though they do 

 not confine themselves to these places. The engraving, fig- 

 ure 157, shows a Mealy-bug, with its powdery covering 

 removed and much magnified. One species D. de- 

 structor, Com stock is one of the worst enemies to the 

 orange groves in Florida. 



Professor Comstock, in his Report as Entomologist of 



