Mites Infesting Flour and Mill Feed 21 



illation revealed t,he fact that it was heavily infested with mites which 

 increased the moisture content of the material and probably contributed 

 to the "heating." 



The small size of mites and their habits of life make them diffi- 

 cult to combat. The females usually lay from twenty to thirty eggs, 

 altho there is reason to suspect that they sometimes lay many more. 

 The eggs are scattered about in the food and are- small oval iridescent 

 structures which sometimes adhere to particles of flour and at other 

 times are entirely free. Their period of incubation varies from three 

 or four days to several weeks depending upon temperature and other 

 factors. 



The larval stage lasts for five or more days and the nymphal stage 

 for six or more days depending upon the variable environmental factors. 

 Thus the entire life cycle may be shortened to about seventeen or 

 eighteen days under the most favorable conditions of high temperature 

 and humidity. 



The life cycle does not always proceed uninterruptedly as outlined 

 above, for there is often a hypopial or resting stage. In this stage the 

 structure is slightly altered in that the chitinous covering is thick and 

 suckers are present by means of which the mite may be attached to 

 insects or mice for transportation to new and favorable environment. 

 During this stage as well as in short periods at the close of the larval 

 and nymphal periods the mites may be blown about with dust. 



When the mites are present in large numbers they often devour 

 practically all of the material so that the result is a mass of mites to- 

 gether with their molted skins. In a warehouse where sacks of cotton- 

 seed cake were stored, the mites were found in piles beside the sacks. 

 By continually falling to the floor a pile of mites had accumulated four 

 inches in height. From this they were crawling awav in every direc- 

 tion. Upon the basis of averages of the number of mites in five sample 

 areas two inches square, it was found that there were 64 mites to the 

 square foot at a point three feet from the base of the pile of cotton-seed 

 cake. 32 to the square foot four feet from the pile, and 8 to the square 

 foot six feet from the pile. Beyond this point the floor was of dirt 

 and it was impossible to determine the number of mites. 



Laboratory observations on five mites showed that they were 

 capable of crawling, on an average, two inches a minute. This, taken 

 with the observations in the warehouses, makes it evident that mites 

 can crawl from one consignment of goods to another while they are 

 in the warehouse. 



The food list of Tyroglyphus contains nearly all food products 



