OBSERVATIONS ON 

 MITES INFESTING FLOUR AND MILL FEED^ 



By R. N. Chapman 



Mites belonging to the family Tyroglyphidae have been well- 

 known pests of flour, grain, and other food products since early in the 

 eighteenth century. They were reported as very numerous in Mil- 

 waukee in 1885.- When present they are often very numerous, some- 

 times causing the so called "grocers itch" which is said to be due to 

 mites accidentally getting on the hands of those who handle infested 

 groceries. Frcjm the fact that some of these pests have been found 

 infesting cheese in large numbers, they are often called "cheese mites" 

 but it would seem more appropriate to speak of them as "flour mites." 



These mites seeui to be well fitted for life in stored food products 

 and for distribution in commerce. They have evidently been distrib- 

 uted all over the globe wherever there is trading in wheat, flour, dried 

 meats, dried vegetables, and other similar products. They are doubt- 

 less much more prevalent than we ordinarily believe, for their presence 

 is often overlooked because of their small size; and the damage which 

 they do is often ascribed to some other cause. 



Within recent years a considerable amount of work has been 

 done on mites in England. This work began during the war and was 

 directed principally toward the damage to wheat and flour. Our 

 knowledge of the habits of these pests has been materially enlarged 

 by this work which has tended to show that mites are restricted to 

 flour and feed with a moisture content of more than eleven per cent. 

 The use of heat and hermetical sealing have also been suggested as 

 means of control and the laboratory experiments with these means 

 have shown that such methods are promising. 



In 1920 it was found that mites were very common in flour and 

 feed mills which were examined for them. Dr. Ewing examined some 

 of the specimens obtained and pronounced them species of Tyrolgly- 

 phus. In only two cases did the proprietors of the mills realize that the 

 mites were present. In one case a large amount of bran had been spoiled 

 and it had been thought that it was due to "heating." A careful exam- 



1 I'tiblished with tlic .mii|i1()v;i1 <if tlie IMrector iis Pajicr No. 'jrA, at the .Imiriial 

 Series of the Minnesota .Xfjrric iiltnial Kxperinient Station. 



2 Riley, 1S^8. 



20 



