336 THE MITES 



good, and alcohol, camphor and other cooling applications are 

 also useful. 



Since in many instances the adults are unknown, the larval 

 harvest mites are, for the sake of convenience, placed in a col- 

 lective group, Leptus, and the name is used in the manner of a 

 generic name. The common red-bug of Europe, for instance, 

 which is supposed to be the larva of Trombidium holosericeum is 

 known as Leptus autumnalis. The most abundant species of 

 red-bug in the United States is Leptus irritans. It occurs through- 

 out the southern United States and as far north as New Jersey 

 and the upper Mississippi Valley. An allied species, Leptus 

 americanus, also occurs in many parts of southern United States. 

 On the northern border of its range this mite does not appear 

 until the latter part of June and becomes especially annoying 

 during August, but its season becomes earlier and earlier the 

 farther south it occurs. 



The European harvest mites, the commonest of which is Leptus 

 autumnalis (Fig. 136), are well known pests throughout Europe, 

 especially in Central and Western France, where they are known 

 as the " betes rouges " or " rougets." They are said to attack 

 small mammals, such as rodents, by preference. Unlike the 

 American species, the European harvest mites become espe- 

 cially abundant in the fall of the year. Japanese investigators 

 have recently cast doubt on the commonly accepted belief that 

 Trombidium holosericeum is the parent of Leptus autumnalis since 

 in Japan the parent of the kedani mite (Fig. 137), which very 

 closely resembles L. autumnalis, is quite different from T. holo- 

 sericeum, whereas an adult mite which very closely resembles 

 the latter, produces larvae quite different from L. autumnalis. 



The Japanese harvest mite, larva of Trombidium akamushi, 

 known locally as the akamushi (red-mite), tsutsugamushi (sick- 

 ness mite) and kedanimushi (hairy mite), has been proven to be 

 the carrier of a typhus-like disease known as kedani or flood 

 fever. These larval mites occur in countless numbers on the 

 local field mice, Micromys montebelloi, living especially on the 

 inside of the ear. They frequently attack the farm laborers 

 who engage themselves in harvesting and handling the hemp 

 which is raised on the flood plains of certain Japanese rivers. It 

 is among these people that the kedani or flood fever occurs, 

 always following the bite of a mite. The bite, usually in the 



