PLANT LICE. ; 161 
“The complicated details noted above were only obtained 
after years of painstaking research, conducted by the late Prof. 
Riley in this country and many careful investigators in France. 
“Means of Dispersion. The distribution of phylloxera is, 
first, by means of the winged females; second, by the escape, 
usually in late summer, of the young root lice through cracks 
in the soil and their migration to neighboring plants; third, by 
the carrying of the young leaf-gall lice by winds or other agencies, 
such as birds or insects, to distant plants; fourth, by the ship- 
ping of infested rooted plants or cuttings with winter eggs. By 
the last means the phylloxera has gained a world-wide distribu- 
tion; the others account for local increase. 
“Remedies and Preventives. The enormous loss occasioned 
by this insect when it reached the wine districts of the Old 
World led to the most strenuous efforts to discover methods of 
control. Of the hundreds of measures devised few have been 
at all satisfactory in results. The more important ones are the 
use of bisulphide of carbon and submersion to destroy the root 
lice; and, as preventive measures, the use of resistant American 
stocks on which to graft varieties subject to phylloxera and the 
planting of vineyards in soil of almost pure sand. 
“Bisulphide of Carbon.—The use of this liquid insecticide is 
practicable only in soil of such consistency as to hold the vapor 
until it acts on the root lice and yet friable enough to afford it 
enough penetration. It will not answer in compact clay soils, in 
very light sandy ones, or in soils liable to crack excessively. The 
liquid is commonly introduced in the soil by hand injectors at 
any season except that of blooming or of ripening of the fruit. 
Sometimes sulphuring plows are used, or the liquid is mixed 
with water and the soil about the vines thoroughly drenched. 
The great volatility of the bisulphide enables it to penetrate to 
the minutest roots, and the lice quickly perish. Four or five in- 
jections of one-fourth ounce each may be made to the square 
yard over the entire surface of the vine yard, inserting the im- 
plement from 8 to 12 inches and not approaching within one 
foot of the base of the vine. The opening in the soil must be 
promptly closed with the foot. A large number of small doses 
is preferable to a few large ones. This treatment will ordinarily 
ae to be repeated every year or two, and is therefore expensive 
