PROCEEDINGS OF THE THIRD ENTOMOLOGICAL MEETING 757 



and cannot go down again. The grain is therefore automatically freed 

 of such insects. 



It should be remembered that the principal infection, and in the 

 majority of cases the primary infection, takes place after the grain is 

 harvested and when it is allowed to be exposed either in the threshing 

 yard or in the godown. Storing should be done directly from the thresh- 

 ing yard. Another point to remember is that the sun is a very good 

 insecticide of which all can make use and the grain should be stored 

 while hot after exposing it to the sun, if possible in thin layers so that 

 all the grains may be heated. 



If it is not intended to mix the grain with sand, a sheet of cloth can 

 be spread over the grain and the sand placed above the cloth. In 

 actual practice it has been found to be equally effective in the case of 

 wheat, as will appear from Experiment XV, 2 and 17. The insects, 

 at least the rice weevils, somehow crawl out and do not breed in the 

 grain. If the top of the bin is made in the manner shown in Plate 123, 

 fig. 2, the sand will remain in touch with the grain all round the edges 

 while the grain in the bin will remain free from sand. In such bins a 

 sheet of iron or tin or a wooden plank can be used in place of the 

 sheet of cloth. When the grain is stored directly from the threshing 

 floor, as recommended here, cloth for such bins can always be used. 



If, however, the grain is already- badly infected, sand allowed to 

 percolate down through the grains will force out more insects. It is, 

 however, better not to use sand in the case of badly infected cereals, 

 as sand gets into the holes produced by the insects in the grains and 

 cannot be removed easily. Badly infected cereals cannot be freed of 

 insects entirely by sand and breeding and damage may continue under 

 .sand as the inSects, especially the weevils, find enough room to move 

 about in the interspaces among the eaten grains. In such cases the 

 grain should first of all be freed of insects either by fumigation where 

 feasible or by breaking up the eaten grains and shells in a pestle and 

 mortar, winnowing ofi the dirt and chaff and then thoroughly heating 

 the grain in the sun or, better, over a fire. It can then be stored with 

 cloth and sand to prevent re-infection and further damage. 



The mud bins of Bihar (Plates 112, 113) and bins made of bamboo or 

 sticks of other plants and the Bihar Bakharis are not good for storage 

 purposes, at least for cereals. Whatever be the receptacle used, it 

 should have the bottom and walls in one piece and without cracks or 

 inter-spaces through which insects can creep in. Mud-walled storage 

 bins can be built inside houses as shown in Plate 124, fig. 1. The 

 empty space below is for aeration so that the grain may not be 

 a fleeted by damp. Similar masonry storage bins can be built with 



