INSECT ENEMIES AND THEIR CONTROL 113 
chemical reaction of the sulphuric acid and water and it 
is important for the liquid to cool considerably before the 
cyanide is added in order to prevent too rapid generation 
of the gas. 
Some growers drop the cyanide into jars without the 
use of paper bags or packages. It is much safer, how- 
ever, to use paper containers, for these will resist the 
action of the acid for a few seconds and make it a safer 
operation for the fumigator. The proper amounts of 
cyanide may be weighed on suitable scales or it may be 
more convenient to have them prepared in proper 
amounts by the druggist. 
When everything is in readiness, all doors are closed 
and locked except the ones through which the operator is 
to pass. If there are several rows of crocks there must 
be a man for each row. The 
packages are carried in a basket 
or a convenient receptacle, and 
the operator usually starts at the 
end of the house farthest from 
the packing or service rooms. He 
passes rapidly from vessel to ves- 
sel, carefully placing a packet in 
each crock so as to avoid splash- 
ing the contents or breathing the 
gas that might escape before he 
proceeds to the next crock. After 
the last crock is passed, he leaves 
the house and locks the door _ fig, 35,—Female nematode 
which has been left open for his (Heterodera radicicola) mag- 
: ‘ nified 85 diameters: a, 
exit. The house should be care- mouth; &, spherical sucking 
Z bulb; c, ovaries as seen 
fully guarded for a few hours. through the body wall; d, 
ie, sin ws : anus; @, small white spots 
Chere is absolutely no danger in Showing’ approximately _ the 
is oO aes : Te — Natural size of these worms. 
this operation if proper care is ex Pe eke oct ie 
ercised. is generally not difficult to 
S ; - isolate them in water by 
some growers prefer to raise breaking open the galls con- 
iteamentiiation im two or three. sian; oo falar xe A: 
