MITES 1013 



and with soft, often velvety skins, frequently of scarlet and other 

 brilliant colours. The large Trombidium holosericum is a well-known 

 microscopical object. The Tetranychi are usually included in this 

 family ; they are, however, rather doubtful members ; they are the 'red- 

 spiders ' of our greenhouses, much dreaded by horticulturists. Each 

 foot is provided with about four singular hairs with round knobs at 

 the end. Bryobia is an allied genus found in great numbers on ivy 

 &c. in gardens and is a beautiful object. The hexapod larvae of several 

 species of Trombidium often attach themselves temporarily to the skin 

 of animals, including man, and produce intolerable itching. They were 

 supposed by the earlier Acarologists to be all one species, and to 

 be adult, and to form a distinct "family ; they were called Leptus 

 autumncdis, and are known in England as the ' harvest-bug/ and 

 in France as the rouget. The Bdellidce are also included in this 

 family ; some authors also include the Cheyleti, which, however, seem 

 to need a separate family, having many curious characters, including 

 the dorsal position of the male organs. 



The Hydrachnidce, or water-mites, as well as the Trombidiidce, 

 have the two stigmata in the rostrum ; the legs are swimming 

 organs, the sexes often very different ; they live in fresh water and 

 are often parasitic in their immature, but not in the adult stages. 

 They are mostly soft-bodied and often of brilliant colours. 



The Limnocaridce are sometimes treated as a sub-family of the 

 Hydrachnidce, but are crawling, not swimming creatures, and are 

 found in fresh water ; but the ffalicaridce, which either constitute 

 a sub-family of, or are closely associated with them, are marine, 

 and are much found among Hydrozoa, on which they probably 

 prey. 



The parasitic Myobiidce are by some included in the Cheyletidce ; 

 the differences, however, are very considerable. They are the last 

 tracheate family. 



The Tyroglyphidce are the cheese-mite family ; they are far the 

 most destructive of all Acarina, swarming in countless numbers and 

 devouring hay, cheese, drugs, growing plants and roots, &c. ; the 

 genus Glyciphagus contains many singular and interesting forms, as 

 G. platygaster and G. Krameri, found in moles' nests. It is in this 

 family that the curious hypopial stage exists ; some of the indi- 

 viduals of some species, instead of following the ordinary life-history, 

 are changed at one ecdysis into a totally different-looking creature, 

 with a highly chitinised cuticle and rudimentary mouth-organs, 

 which can endure draught and other unfavourable circumstances 

 which would kill the ordinary form. They attain the same adult 

 stage as other individuals. The Hypopus is provided with adhesive 

 suckers whereby it attaches itself temporarily to other creatures, and 

 this serves for the distribution of the species. 



The Tarsonemidce are minute creatures, some leaf-miners, some 

 parasitic on bees &c. 



The Sarcoptidce are divided into two great sub-families, the Sar- 

 coptince, or itch-mites, of which the well-known Sarcoptes scabiei of man 

 (Plate XXII, fig. 4) is the type, and the Analgesince, or bird-parasite 

 mites; all have soft bodies with finely striated cuticles. Sarcoptes 



