34 « 
Another interesting point in connection with the life history of 
Pimpla conquisitor is the fact that it occurs both as a primary and 
a secondary parasite on the same host, Clistocampa americana. Very 
small individuals were bred from several species of primary parasites 
attacking the immature caterpillars, the species most commonly act- 
ing as host in this manner being Limneria fugitiva. 
The next paper, by Mr. Fernald, was entitled: 
ON THE MARGUERITE FLY. 
By H. T. Fernaup, Amherst, Mass. 
[ Withdrawn for publication elsewhere. ] 
Replying to a question from Mr. Johnson, as to whether hydrocy- 
anic-acid gas had been used, Mr. Fernald stated that there was objection 
to the use of this substance among florists, who have an exaggerated 
idea of the danger involved and will not often use it. He had no 
doubt hydrocyanic-acid gas would be more effective, but thought the 
florists would prefer to use carbon bisulphide, as this substance had 
proved satisfactory. 
Mr. Fletcher thought that remedial work against the flies during 
the winter would be better than work against the larve after they 
have eaten the leaves. 
Mr. Fernald replied that the problem had been thus far looked at 
by him entirely from the florists’ standpoint, and the insect treated in 
the stage at which the florists would first see it and want to treat it. 
He was certain, however, that the fly could be handled by fumigating 
the greenhouses. 
Mr. Woodworth said that the fear that exists in the East over the 
use of hydrocyanic-acid gas was looked upon by many Californians as 
very funny. In his State the greenhouse man will pick up his mate- 
rial in his hands, charge his vessel, walk out deliberately, and close 
the door after him. 
Mr. Johnson stated that one could not be too careful in the use of 
hydrocyanic-acid gas, and he wanted to caution all those who used it. 
In one instance, after preparing the chemicals necessary for generating 
the gas, he thought he would take his chances in dropping the cyanide 
in the jar and get out, but he felt the effects of the gas almost imme- 
diately. By the time he reached the door a haze came over his eyes, 
everything looked black, and a feeling similar to blind staggers over- 
came him. Experience has proved that it is not a trifling matter, and 
he would caution all who had occasion to use the gas. At the same 
time he felt that hydrocyanic-acid gas was the coming material for the 
destruction of certain insect pests in mills where stored grain and 
