HARVEST MITES 333 



sitism has apparently arisen independently in different families 

 and genera at least eleven times. Nathan Banks in his treatise 

 on the Acarina, after giving a number of interesting examples of 

 peculiar parasitic habits, writes as follows: " We can only explain 

 these remarkable habitats by the fact that mites, especially in 

 their immature stages, have an incontrollable desire to go some- 

 where, and get into every cavity and crack they discover in their 

 wanderings. When hungry they test their locality for food, and 

 if not too different from their previous diet this new habitat may 

 result in new species and genera." 



A few species of mites have become adapted to live as internal 

 parasites, but all the species normally infesting man are either 

 external or subcutaneous in their operations. A few of the 

 species which are not averse to human beings as food are 

 troublesome and irritating enough to bring their whole tribe into 

 disrepute. The families of mites which contain species annoying 

 to man are the Ixodidce and Argasidce, the ticks; Trombidiidce, the 

 harvest mites and " red-bugs "; Parasitidce (Gamasidce), including 

 the chicken mites; Tarsonemidce, including the louse-mite; Ty- 

 roglyphidce, including the cheese and grain mites; Sarcoptidce, the 

 itch mites; and Demodecidce, the hair-follicle mites. For con- 

 venience we may include with the mites the very aberrant arach- 

 nid ^forms known as tongue-worms, now usually placed in a 

 distinct order, Linguatulina. Since the ticks are popularly looked 

 upon as quite distinct from other Acarina, and form a very im- 

 portant group of the order on account of their role as disease 

 carriers, they will be considered in a separate chapter. 



Harvest Mites 



The six-legged larvae of the harvest mites, family Trombidiidse, 

 known as red-bugs or chiggers, are very annoying pests, and one 

 species, the Japanese " akamushi " or kedani mite, has been 

 proved to be the carrier of a dangerous disease, kedani or flood 

 fever. Harvest mites are little scarlet-red animals, and their 

 larvae are tiny pale-colored creatures bare'y visible to the naked 

 eye (Fig. 136). According to one writer who had evidently 

 experienced them a red-bug is a " small thing, but mighty; a 

 torturer a murder of sleep ; the tormentor of entomologists, 

 botanists and others who encroach on its domains; not that it 



