190 



INJURIOUS INSECTS OF 1904. 



lady who was troubled with the above pests in her greenhouse. 

 The Violet Gall is caused by the larva of a small two-winged fly, 

 which rolls up a violet leaf and lives within. Rotting of the leaf 

 is apt to follow this imperfect gall. 



Mr. Ruggles first accurately determined the cubic contents of 

 the greenhouse, and then fumigated with hydrocyanic acid gas at 

 the rate of 0.15 grams (2,325 grains) to a cubic foot of space. The 

 cyanide of potash, sulphuric acid and water were used in the pro- 

 portion of 1-1^-2, and the exposure was 35 minutes. As results 

 proved, 25 minutes, the prescribed time, would perhaps have been 

 better, since some of the more tender growth was injured. 



Some of the Aphids svirvived the above treatment, though 

 many perished. The insects causing the galls were apparently 

 killed, though the difficulty appeared after the above treatment, 

 calling for a second application. 



GRAIN PLANT LOUSE. 



A few reports of the occurrence of this insect have been mailed 

 the Experiment Station by parties who were somewhat alarmed 

 at seeing them on heads of wheat. As usual, they have been taken 

 care of by parasites, and their presence has resulted in no serious 

 harm. 



Ij-^ ■ /fit' 



Fig. 177. — Grain Plant Lice from which parasites have issued. 



