39 



better than the heavier coat experimented with in this instance and 

 perhaps might have proven of some slight value in preventing the set- 

 tling of the young scales. Further than this the pure lime wash 

 appears to be of little value against scale insects, at least as indicated 

 by this single test. (See PL II.) 



The insecticide value of formaldehyde gas. — Some experiments were 

 made in conjunction with Dr. E. A. de Schweinitz, of this Department, 

 several years since to determine the insecticide value of formaldehyde 

 gas. The results of these early trials indicate little, if any, value in 

 this gas for the purpose named. This year opportunity was offered 

 to test this gas in a much more satisfactory way. A patent generator 

 having been devised by some local parties especially for germicide 

 purposes, the owners were very anxious to have it tested, also to deter- 

 mine its value as a means of destroying insects. Under the writer's 

 supervision, therefore, it was used in the first instance against insects 

 affecting stored products. The gas was generated to three or four 

 times the amount necessary- for germicide purposes in the fumigating 

 room of the Department which contained some grain badly infested 

 with the Angoumois grain moth and some beans thickly stocked with 

 the bean weevil. The gas killed some of the moths which were flying 

 about thickly when the generator was put in operation, but the bean 

 weevils were apparently not injured in the least by it and a good many 

 of the moths were not killed. The generator was subsequently placed 

 under a tented peach tree thickly infested with Diaspis pentagona. 

 The generation of the gas in this instance was again in enormous 

 quantity for the space inclosed, a quart of alcohol being converted. 

 The effect on the tree was, however, most disastrous, the leaves show- 

 ing almost complete withering as soon as the tent was removed and 

 the tree dying shortly after. The scale insects were immediately 

 killed by the application, and therefore not as a result of the death of 

 the tree. The effect on the scale insects and the tree may have been, 

 and was, very likely, due to the heat which the generation of the gas 

 produces. This gas is generated by the imperfect combustion of wood 

 alcohol in a burner or stove especially designed for the purpose. The 

 insects in the fumigatorium and the scale insects on the tree were 

 subjected to the influence of this gas between three and four hours. 



A recent bulletin of the Hatch Experiment Station of the Massachu- 

 setts Agricultural College (No. 69) would seem to indicate that this gas 

 has little or no value as a fungicide. 



THE CARRIAGE OF DISEASE BY FLIES. 



By L. O. Howard. 



So much is said nowadays of the carriage of a certain class of dis- 

 eases by mosquitoes that the agency of certain flies in the transmis- 

 sion of another class of diseases is apt, to a certain extent, to be 



