ACARINA. 851 



genera with but a single species ; Hydrachna with 33 species, Thyas with 

 8 species, Panisus with 4 species, Protzia with 2 species, Eupatra with 4 

 species, Hydryphantes with 17 species, Krendowskia with 3 species, 

 Arrhenurus a very large genus with about 100 species, Aturus with 4 

 species, Torrenticola with 2 species, Lebertia with 6 species, 0#w$ with 

 8 species, Teutonia with 2 species, Sperchon with 14 species, Limnesia 

 with 12 species, Atractides with 5 species, Hygrobates with 11 species, 

 Hydrochoreutes with 3 species, Pionacercus with 4 species, Laminipes with 

 5 species, -4ta# with 27 species, the well-known .4ta# 6ow2* infests fresh- 



water mussels (Fig. 554) ; Neumania with 11 species, Feltria with 10 species, 

 Tiphys with 9 species, P*ona with 34 species and Pontarachna with 3 

 species. 



Fam. 8. Halacaridae.* Marine, the head bearing the chelicerae 

 and pedipalps (the capitulum) is movably articulated with the body, 

 usually an anterior and a posterior 

 dorsal, hard, sclerite, and two side 

 ones protecting the eyes, legs attached 

 to the side of the body. This is a 

 comparatively small family of marine 

 mites which do not swim but crawl 

 about on sea-weed and hydroids, 

 ascidians, etc. They are for the most 

 part predaceous, but Bhombognathus 

 eats sea-weeds. They are widely dis- 

 tributed both horizontally and verti- 

 cally. Halixodes, Atelopsalis, Acarom- 

 antis have each one species, Coloboceras, 

 Scaptognathus and Simognathus each 

 two, Trouessartella three. Agaue seven, 

 and Halacarus 41 species. F I( J. ws.Cheyletus flabellifer (Book 



Fam. 9. Bdellidae. These long-nosed Mite quite unconnected with books). 

 or snouted mites are distinguished by 



the marked separation of their " capitulum " or " head " from the rest 

 of the body, chelicerae chelate and long and projecting, pedipalps tactile 

 and elbowed ; usually bright in colour, often red ; larvae attach themselves 

 to spiders and beetles but the adults are free and predaceous. Scirus, 

 Bdella, Ammonia, Eupalus, Cheyletus (Fig. 563) sometimes placed in a 

 separate family, Cryptognathus, Eupodes and others. 



Sub-order 5. ASTIGMATA. 



Degenerate, usually parasitic mites which approach the Prostigmata in 

 the development of the integumental sclerites, soft skin, no tracheae. 



Fam. 10. Sarcoptidae.f Rounded posterior end of the body ; legs 

 mostly 5-jointed with 1 or 2 claws ; eyes seldom found ; sexes usually 

 markedly different. Most parasitic on or in the skin of Mammals, Birds 

 and Insects. There are numerous sub-families. Sub-fam. 1. Cytolichinae, 

 Cytolichus and Laminosioptes each with one species. Sub-fam. 2. Sareo- 



* Piersig and Lohmann, Das Tierreich, 13 Lieferung, Hydrachnidae 

 and Halacaridae. 



f Canestrini and Kramer, Demodicidae and Sarcoptidae (including 

 Tyroglyphidae) Das Tierreich 7th Lief . 1899. 



