34 



Another interesting point in connection with the life history of 

 Pim])la conquisitor is the fact tliat it occurs both as a primarj^ and 

 a secondary parasite on the same host, CUsiocampa 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 Limneriafugitiva. 



The next paper, by Mr. Fernald, was entitled: 



ON THE MARGUERITE FLY. 



By H. T. Fernald, Amherst, Mass. 

 [Withdrawn for pulilication elsewhere.]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 

 dou))t hydrocyanic-acid gas would be more eflective, 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 larviK 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 efl'ects 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 



