GRAIN MITES 339 



detachments of mites are constantly acquired. In severe in- 

 festations the irritation and poisoning is sufficient to cause 

 constitutional symptoms such as fever, high pulse, headache, 

 nausea, etc. 



Since the mites cannot thrive on human blood, and remain 

 attached to the skin for only a short time, no treatment for 

 destroying them is necessary. Remedies to relieve the itching, 

 such as the application of soda or soothing ointments, or warm 

 baths with a little soda, are called for. To prevent infection 

 when handling infected produce, Dr. Goldberger, of the United 

 States Public Health Service, suggested a greasing of the body, 

 followed by a change of clothes and a bath after working with 

 the infected material. Riley and Johannsen suggest the use of 

 powdered sulphur as a preventive in view of its efficiency against 

 harvest mites. Control of the mite consists largely in keeping 

 grain and other dry produce as free as possible from the insects 

 on which the mites feed. Burning stubble in winter and threshing 

 wheat directly from the shock would tend to lessen the worms in 

 stored wheat and with them the mites. 



Grain Mites. The family Tyroglyphidse, including many 

 species of mites which normally feed on grain, flour, sugar, dried 

 fruits, cheese and other foods, contains 

 several species which become annoying to 

 man and produce an itching rash on people 

 who handle infested goods. 



According to Banks all the members of 

 this family are pale-colored, soft-bodied 

 mites, with prominent pincer-like chelicerse 

 and no eyes. Their bodies are about 

 twice as long as wide and are furnished 

 with a few scattered long hairs (Fig. 140). 



mi Tf i j. f i- f A.-L- FIG. 140. Grain mite, 



The life history of some members of the T yrogiy P hus longior. x so! 

 family is quite remarkable in that there is (After Fumouze and 

 added a phase of existence which does not 



occur in other mites. All the species scatter their eggs haphazard 

 over the infected material. Upon hatching the larvse have six 

 legs and acquire a fourth pair after moulting, in orthodox mite 

 style. Some now develop directly into adults, while others go 

 through what is called a " hypopus " stage. The hypopus (Fig. 

 141) is very different from the nymph from which it develops: 



