ENTOMOLOGY. 1075 



Among other natural enemies of the Hessian fly are mentioned nema- 

 tode worms and thrips. 



As to artificial remedies, the author recommends the burning of stub- 

 ble as soon after the cutting of the grain as possible in case of a moist 

 season. This remedy is not so necessary during a dry season. In cer- 

 tain eases it may be advisable to plow under the stubble. In order 

 that this may be effective the ground should be plowed to a depth of 

 several inches. It is also recommended that all volunteer wheat be 

 destroyed in order that belated individuals may not find a food supply. 

 The author further recommends a rotation of crops such that wheat 

 shall not come 2 years in succession on the same ground, and also that 

 fall wheat should preferably be sowed late rather than at the begin- 

 ning of the fall season in order to avoid attacks of the Hessian fly 

 upon the young developing wheat. Such remedies as pasturing fall 

 wheat with sheep, rolling the wheat with a heavy roller in the fall, and 

 mowing the young wheat are considered by the author as being of but 

 little avail. It is stated that certain varieties of wheat have been found 

 to be more resistant to the attacks of the Hessian fly than others, and 

 a selection of varieties may be made accordingly. 



Of the various insecticides which have been used, none have ever 

 been effectual and none are therefore to be recommended. 



A rather complete bibliography of the literature on the Hessian fly 

 is appended to the bulletin, containing 141 titles. 



The use of hydrocyanic-acid gas for fumigating greenhouses 

 and cold frames, A. F. Woods and P. H. Dorsett ( l T . 8. Dept. Ayr., 

 Division of Entomology Giro. 37, 2. ser., pp. 10, Jigs. 3). — Greenhouse 

 plants were less injured by a short exposure to a large amount of gas than 

 by a long exposure to a small amount of the gas, and at the same time 

 the insects were more thoroughly destroyed by the large amount of gas 

 for a short time. It was found that fumigation after sundown with the 

 temperature as low as practicable gave the best results. For ferns 

 0.075 gm. of 98 per cent cyanid of potash was used for each cubic foot 

 to be fumigated. The ferns were infested with Chionaspis. All the 

 insects were destroyed. Coleus and other related plants were fumi- 

 gated at the rate of 0.1 gm. of 98 per cent cyanid of potash per cubic 

 foot of space. Double English violets were fumigated at the rate of 

 0.15 gm. of 98 per cent cyanid of potash for each cubic foot of space. 

 Roses were found to be especially sensitive and many of them were 

 more or less injured in all of the experiments. Carnations were found 

 to endure 0.1 gm. of cyanid of potash per cubic foot for 15 minutes. 

 Grapes under glass endured 0.09 gm. per cubic foot. Tomatoes with- 

 stood 1 oz. of pure cyanid of potash for each 1,000 cu. ft. Careful direc- 

 tions are given for obtaining the cubic space of greenhouses and for 

 calculating the necessary amount of cyanid to be used in each case. 



The materials to be used are 98 per cent cyanid of potash and com- 

 mercial sulphuric acid. Earthen jars lh or 2 gal. in capacity and of 

 20776— No. 11 6 



