22 ElGHTF.KXTH KeIHIRT StATE KxTOM Ol.OGIST OK MINNESOTA 1920 



made from ])l;ini and animal matter, as dried meats, cheese, dried 

 fruits, ,t,rrain. Hour, and many other substances, including sugar. There 

 would seem to be a reasonable doubt as to whether sugar is really the 

 food of the mites in which they actually grow and reproduce, or 

 whether they have been found in it by accident. 



The moisture conditions of the infested material, as has already 

 been stated, may often be the limiting factor in the development and 

 reproduction of tlie mites. However, they may spend long periods in 

 the hypopial stage in which they can endure dessication. This was 

 strikingly illustrated in a cotton-seed meal warehouse where the meal 

 with various moisture contents was blended, with the result that the 

 mixture had a uniform moisture content of less than eleven per cent. 

 Samples taken from certain car lots of meal with a high moisture con- 

 tent showed mites to be present in fairly large numbers, yet twenty 

 samples taken from the blended meal in various parts of the warehouse 

 failed to reveal a single mite. Later a pile of the meal which had ac- 

 cumulated below a conveyor through which the blended meal was 

 removed from the warehouse, was literally alive with mites after it 

 had been moistened by a rain. From this it seems evident that there 

 were mites present in the warehouse in the hypopial stage but that 

 they did not have sufficient moisture to support them in an active stage 

 until they accumulated on the ground under the conveyor. 



In examining carloads of bran, middlings, and other feed, it was 

 found that the best procedure was to find a spot where the feed had 

 become damp because of a leak in the roof and examine some of this 

 material. If mites were present at all they would be active in such a 

 place as this. If they were not found in the damp feed, the chances 

 were that the material was free from mites. 



In a large percentage of the mills, mites were found when a careful 

 examination was made of the elevator boots and other places which 

 were slightly damp. The best method of examination was to smooth 

 out the surface of the sample with a spatula and examine it carefully 

 with a binocular microscope. Within a few minutes the slow clumsy 

 movement of the mites was evident. When they were present in large 

 numbers a characteristic sweetish odor was evident. When one be- 

 comes accustomed to this he can detect the presence of a bad infesta- 

 tion of mites by his sense of smell alone. 



It has been stated'' that certain predatory mites (Chelytes and 

 Parasitus) will entirely eliminate the tyroglyphid mites. However, the 



3 Kile.v, 18SS. 



