December, '22] larson: metallic mercury as an insecticide 391 



transformed to flies. A few flies were also found in beet fields on August 

 6, 1921. It would seem that a small second brood of flies occurs in 

 most years. 



A beet field near Lewiston which had a very heavy infestation of 

 maggots in 1921 was fall-plowed and seeded to wheat. This spring 

 flies were abundant and a few eggs were found around weeds in the 

 wheat but none around the grain itself. Eggs were also present near 

 weeds in a potato field across the road. The nearest beet field was 

 forty rods away, and here flies and eggs were unusually abundant. 

 It would appear that flies sometimes migrate some distance to find 

 suitable breeding places. 



The control of Tetanops has received little attention up to the present 

 time. Solutions of corrosive sublimate and other materials that may 

 act as ovicides or larvicides were placed around plants on June 6, 

 but the action of these cannot be observed for some time. It is hoped 

 that when we know more about the insect some cultural practice may 

 be found which will furnish an effective and cheap control. 



Tetanops is apparently a native insect which has fed on weeds for 

 many years and which is now adding the beet to its list of host plants. 

 We rather feel that if early indications are fulfilled, it will this year 

 take its place as one of the three most serious insect pests of beets in 

 Cache Valley. 



METALLIC MERCURY AS AN INSECTICIDE 



By A. O. Larson,! Assistant Entomologist, United States Department of Agriculture 



Dr. K. Kunhi Kannan of the Department of Agriculture of Mysore 

 State, while visiting our laboratory in 1920, mentioned the fact that he 

 had successfully prevented the hatching of Bruchid eggs in India by 

 placing a small amount of metallic mercury in the container. While he 

 was unable to give the identity of the Indian Bruchid, he said that it 

 glued its eggs to the bean as does B. quadnmaculatus. He said that 

 without the mercury appreciably decreasing in quantity, its presence 

 in a container completely prevented the development of the eggs. 

 He said that this action of mercury had been a tradition among his 

 people. 



As a result of this information three experiments with mercury and 

 the eggs of B. quadnmaculatus were carried on at the same time, as 

 follows : 



iThe first experiments were conducted by Perez Simmons.and the last cowpeas were 

 dissected by A. H. Amis. 



