MITES AND TICKS 



423 



when hatched, but soon gain another pair. When some mites are 

 starved or desiccated, and to some extent die, certain cells in the body 

 unite within a cyst, and are able in favourable conditions to regrow the 

 animal. 

 Examples — 



(a) Without tracheae. Cheese-mite {Tyroglyphus). Itch-mite 

 (Fig. 235) {Sarcoptes scahiei), causing "itch" in man; S. 

 cams, causing " mange " in dogs. Follicle-mite {Demodex 

 folliculorum), common in the hair follicles of man and domestic 



pit' 



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 (•.:v^-,i'f..:-7 



•*...' • • • • j§ 



m 



■'-■■■-■■.•:( 

 '•'■'■'-'■i 



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Fig. 234. — Follicle-mite Fig. 235. 



(greatly enlarged). 



-Itch-mite (Sarcoptes scabiei) 

 (greatly enlarged). 



animals (Fig. 234). Gall-mites (Phytoptids), forming dimples 

 and pouches on plants. 

 {b) With tracheae. Harvest-mites {Trombidium), whose minute 

 hexapod larvaj are troublesome parasites in summer on 

 insects, many mammals, and man. The so-called " red 

 spider " {Tetranychus telearius) spins webs, and lives socially 

 under leaves. Water-mites, e.g. Hydrachna on water- 

 beetles, and Atax on gills of fresh-water mussels. Beetle- 

 mites {Gamasiis), often found on carrion beetles and on 

 humble-bees. There is a common red mite on the shore- 

 rocks, known as Molgus (Bdella) litioralis. 



