mg more severe annoyance than adults, and young- women as a rulesutt'er 

 morethanolder persons. People with thin, delicate skin and florid com- 

 plexion are most afflicted by the mites, and with thein the congested 

 red spots are proportionately larger and more inflamed and irritating. 



Many persons, however, as, for example, permanent residents of 

 infested regions, and particularly farm laborers, seem to be practically 

 proof against the toxic efl:ects of harvest mites and go with impunity 

 into places overrun with them. This immunity to poisoning is obvi- 

 ously due to two causes: (I) To outdoor work which toughens the per- 

 son's skin, especially such portions of the arms and legs as are much 

 exposed to the sun and weather; and (2) to inoculation, due to fre- 

 quent infection. 



The inflamed spots due to the presence of the mites under the human 

 cuticle are often diagnosed as hives, nettle- 

 rash, urticaria, oi"the " weals," and resemble 

 closel}^ those produced on man}^ persons by 

 the "bites ''of fleas and some mosquitoes; 

 but on the second or third day each of the 

 mite-infested areas is usually found sur- 

 mounted at the middle by a minute vesicle 

 or water blister. This is obviously the most 

 important characteristic of harvest-mite at- 

 tack. After the subsiding of the inflamma- 

 tion and itching, which takes place in a few 

 da3's, a small scale or scab frequently forms, 

 leaving on some persons a scar which does 

 not wholly disappear in extrtnue cases for 

 weeks. The mites naturally attack first 

 those portions of the body which are most 

 exposed — those nearest the ground. Thev 

 crawl into the stockings and penetrate the skin about the aid^les, fre- 

 quently ])elow the shoe tops, and are usually found most munerous 

 below the knee. According to the late Dr. John Hamilton, a ph^-sician 

 as well as entomologist, the harvest mites enter the larger sweat tubes 

 or pores of the skin, and as these tubes are very tortuous, the progress 

 of the mites is necessarily slow, from eighteen to thirtj^-six hours being 

 required for them to reach the end. When the lesions caused by these 

 luitcs are unusually numerous, the sufferer becomes feverish, and sleep 

 is much disturl)ed. Sometimes the atflicted one becomes fi'antic and 

 lacerates his flesh by too vigoi'ous and f recjuent scratching. Erj^sipelas 

 is known to follow severe attacks, and death resulting from blood pois- 

 oning is recorded. These more serious results of infestation are, how- 

 ever, exceptional and. us with the fatalities which in rare cases follow 

 the ordinarily merely painful oi' annoying 'M)ites" of many insects, 

 undou1)tedly point to an impurity of the blood. 



[Cir. 77] 



). — Troinbidium: Adult, highly 

 magnified {from Banks). 



