850 CLASS V. ARACHNIDA. 



their attentions to one species of host. Ixodes (Figs. 560, 556) with some 30 

 species is capable of living in comparatively cold countries, this genus is 

 blind, /. ricinus is the common dog tick ; Eschatocephalus (Haemalastor) 

 with 5 species ; Aponomma with 14 species inhabits the warmer regions 

 of the Old World and is often parasitic on snakes and other reptiles ; 

 Amblyomma with over 70 species requires a tropical climate and is largely 

 American and African but it reaches Asia. A. hebraeum is the well-known 

 " Bont-tick " of S. Africa ; Hyftlomma (Figs. 559, 561) 3 species largely 

 African but it also extends into Asia ; Haemaphysalis with 18 species 

 is largely Asian ; Rhipicephalus with 14 species is chiefly African, but 

 spreads to Asia and Europe and has been widely distributed by man. R. 

 annulatus conveys the parasite which causes the Texas or Red-Water 

 fever in cattle, several species attack sheep ; Dermacentor with 7 species. 



Sub-order 4. PROSTIGMATA. 



Stigmata, when present, lie close to or above the bases of the chelicerae : 

 they are absent in some aquatic forms. Integument soft but with sclerites, 

 those on the ventral surface apparently represent the proximal segment of the 

 legs embedded in the body. 



Fam. 6. Trombidiidae. The pedipalps usually have the 2nd joint 

 longest and a finger and thumb arrangement at the tip, some live on plants 

 and some are carnivorous, tarsi 2-clawed and without a caruncle. Tetrany- 

 chus telarius the red "spider" of our hot- 

 houses spins threads from a papilla near the 

 end of the abdomen, many other species of 

 this genus damage plants ; Rhaphignathus , 

 Bryobia with long anterior legs ; Trombidium 

 holosericeum (Fig. 562) is the commonest of 

 the " harvest mites," in its youth it is par- 

 asitic on Phalangids ; Caeculus mimics Pha- 

 langids ; Tarsonemus attacks plants. 



Fam. 7. Hydrachnidae.* Freshwater 

 mites with legs provided with long, closely 

 packed hairs adapted for swimming. Pre- 

 daceous with the earlier stages often parasitic 

 on water insects (Fig. 558). The Hydrachnidae 

 are very widely distributed; they are mostly 

 FIG. 562. Trombidium holoseri- freshwater but some, such as many species of 

 ceum (after Megnin). Hydrachna and of Hydryphantes, and others 



live in brackish water, whilst Pontarachna 



and Nautarachna have marine representatives. They live on other 

 organisms, chiefly on species of Daphnia and Cypris, more seldom on 

 Cyclops, Gnat-larvae and Infusoria. Limnochares 2 species lives in 

 mud, Eulais, young stages parasitic on aerial insects, 35 species ; 

 Piersigia, Diplodontus, Bargena, Thyopsis, Pseudothyas, Partnunia, 

 Tanaognathus, Mamersa, Midea, Xystonotus, Mideopsis, Axonopsis, Aibia, 

 Brachypoda, Ljania, Frontipoda, Gnaphiscus, Pseudosperchon, Limnesi- 

 opsis, Koenikea, Capobates, Tyrrellia, Wettina, Pionopsis, Ecpolus, Encentri- 

 dophorus, Najadicola, Huitfeldtia, Nautarachna and Kongsbergia are all 



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

 and Halacaridae. 



