Mites Infesting Flour and Mill Feed 23 



work carried on in England* does not seem to substantiate this. The 

 observations of the writers have sliown that while these predaceoiis 

 mites do actually destroy some of the tyroglyphids, their effect is most 

 noticeable when the moisture conditions are unfavorable for the tyro- 

 glyphids and the effect is least noticeable when conditions are most 

 favorable. This is indicated by the fact that when hundreds of samples 

 were examined the predaceous mites were most abundant in the dryer 

 material where the tyroglyphids were fewer and the tyroglyphids were 

 most abundant in the moist samples where the predaceous mites were 

 least abundant or entirely absent. In no case, either in the laboratory 

 breeding experiments or in the mills, were the tyroglyphids entirely 

 eliminated by the predaceous mites if the moisture was favorable for 

 the tyroglyphids. 



The damage done to tiour and grain is evidently due partly to the 

 presence of the mites themselves and partly to bacterial action which 

 may be started by the accumulation of their excrement. Beattie'' con- 

 cluded that this was the case in flour which he examined. Humphries" 

 concluded that flour could be reconditioned by passing it through a 

 No. 14 bolting cloth, and that if the moisture content was low this 

 flour would be suitable for human food. 



Much of the material examined by the author was found to have 

 the characteristic mite odor so strong that it seemed impossible to 

 recondition it and use it for food. In fact much of the stock feed 

 which was badly infested was refused by cattle, evidentlv because of 

 the odor. 



Experiments in separating the mites from flour have shown that 

 adults mav be removed by passing the material through a No. stand- 

 ard bolting cloth. To remove the young larvae a No. 9 cloth must be 

 used, and for the eggs a No. 14 cloth. As the presence of adult mites 

 is circumstantial evidence of the presence of eggs, it is not practical 

 to try to get the mites out of any material except that which can be 

 passed through a No. 14 standard bolting cloth. This means that high- 

 grade wheat flour is the only material that can be treated in this way. 



Methods of Combating Mites 



It is generally said that fumigation is not effective against mites 

 owing to their lack of tracheae. Experiments carried out with carbon 



4 Newstead and Duvall lOlS, p. 11. 



5 Beattie, 1918. 



(■> Humphries. 1018. 



