PKOCEEDING.S OF THE THIRD ENTOMOLOCaCAL MEETING 761 



The reason why it is that the weevils come to the top is that they jyir. Kunhi Kannan. 

 want free space to mate. 



When a large quantity of grain is stored and small quantities have Mr. G. R. Dutt. 

 to be taken out at intervals for use, infestation may take place when 

 the sand is removed from the top. Some arrangement by which the 

 graiji can be drawn out from below would be desirable. 



Such an arrangement is possible but not necessary. The grain can Mr. Ghosh, 

 be taken out from the top and re-covered with sand. The bin of wliich 

 Mr. Kunhi Kamian has given a description, with a hole at the lower 

 part closed with a coconut shell, affords a weak point at the hole through 

 which weevils will get in. If it is really desired to have such a hole it 

 should have an arrangement which will allow of the hole being covered 

 with sand. 



38.— MEECURY AS AN INSECTICIDE. (Abstract.) 



Bij K. KuKHi Kannan, M.A., F.E.S., Senior Assistant Entomologist, 

 Mysore. 



While investigating the indigenous methods of storing pulses in 

 Mysore, it came to the notice of the Agricultural Department that 

 raiyats had great faith in the efficacy of mercury as a protection against 

 the pest. The practice appears to have been to place a drop of mercury 

 in an excavated soap-nut in the receptacle used for storing. Further 

 details could not be obtained, as the practice seems to have died out 

 practically. The poisonous effect of mercu^ vapour on human beings 

 being well known, it was decided to test the value of the metal as an 

 insecticide and the results have vindicated what has been long re- 

 garded as a superstition. 



The presence of the metal in very small quantity placed in a dish 

 inside the receptacle prevented the multiplication of the beetles. A 

 series of experiments conducted show that the action is on the eggs 

 of the beetles which are usually laid only on the top surface of the pulses 

 and not on the other Stages. The effect is less marked m the case of 

 large store bins of several cubic feet capacity. But in small jars or 

 pots of a couple of cubic feet or so a drop or two absolutely prevent 

 emergence. The same deleterious action has been noticed on the eggs 

 of silkworms also. Detailed results will be published elsewhere. 



Where do the raiyats get the mercury ? Mr. Fletcher. 



It is sold in the bazaars. Grocers store it. Mr. Kunhi Kannan, 



Is it found in India ? Mr. Fletcher. 



I think so. At one place they had ten pounds of mercury found Mr. Kunhi 

 as metal in one place. Kannan. 



