150 
Psyche 
[June- August 
the two pests were then removed from them in the laboratories. 
In detaching them from the bark many of the cocoons tore 
open, for they were attached very firmly. About 700 cocoons of 
the two species were recovered from about twelve bushels of 
peeled bark. 
For their treatment with calcium cyanide, the insects 
(cocoons) were retained in a coarse muslin suspended on the 
stalks fumigated. No pupae were used in the experiment which 
failed to respond to a gentle pinch with the forceps, prior to 
fumigation. 
The vines . — The vines treated in Switzerland were of a 
species called “chasselas,” indigenous to that country, while in 
France vines with American rootstock were selected. Vines of 
varying ages, from 5 years to 50 years, were treated in order to 
secure information concerning the resistance of plants of varying 
ages to the action of HCN gas. 
In Switzerland the majority of vineyards are of the type 
where the vines are grown singly, trained on wooden supports 
about 1 meter or a little over in height, placed in the ground 
close to the pruned vine just as soon as growth begins in the 
spring. The French methods of cultivation are of three types: 
(1), individual vines (as in Switzerland) pruned close to the 
ground; (2), vines trained on a single line of wire stretched the 
full length of each row; and (3), taller vines trained on double 
lines of wire, the first line about 30-35 c. m. above the ground, 
and the second wire about an equal distance above the first. 
The wires are attached to strong wooden posts in the rows, 
placed about 12-15 meters apart. The majority of vineyards in 
France are of the third type. 
The covering .- — The protection afforded the insects by their 
heavy covering (the cocoons) and also the fact that their res- 
piratory system is at the minimum period of functioning during 
this season of the year (late winter and early spring) and stage 
of their life, made it at once evident that open air fumigation 
would be futile. Consequently a canvas tent and a cylindrical 
galvanized iron can were used in covering the vines for the 
treatments. The tent, of heavy impermeable canvas, was made 
large enough to permit treatment of four vines together. Its 
