ACARINA. 



855 



probably cosmopolitan. D. canis attacks dogs,^ D. 

 caprae the European Capra hircus, D. phylloides the 

 pig, and D. bovis the ox. 



Sub-order 7. TETRAPODA. 



Degenerate mites without tracheae, the body is elongate 

 and the posterior part is ringed, the 3rd and 4th appen- 

 dages are lengthened the 5th and Gth absent. They 

 cause and inhabit plant-galls. 



Fam. 13. Eriophyidae * (Phytoptidae). Fig. 555. The 

 mites of this family form galls, with a single chamber 

 opening to the exterior by a pore protected by hairs. 

 The chamber, unlike those of insect-formed galls each 

 of which contains one insect, contains a considerable 

 number of mites which live on the vegetable hairs 

 growing on the inner wall of the chamber. Eriophyes, 

 with some 150 species on all sorts of plants ; E. tiliae 

 forms the well known " nail " galls on the Lime leaf 

 and E. ribis is at present doing much harm to black 

 currants in Great Britain ; Monochetus with one species 

 on the Beech ; Phyllocoptes some 50 species on many 

 plants ; Anthocoptes many species on trees ; Tegonotus 

 3 species on three natural orders of plants ; Epitri- 

 merus 14 species on nine different natural orders ; Oxy- 

 pleurites 6 species on 5 different natural orders ; and 

 Paraphytoptus one species on Artemisia. 



FIG. 567. Demodex 

 folliculorum (after 

 Mgnin), strongly 

 magnified ; Rt, 

 pedfpalpus. 



APPENDIX I TO THE ARACHNIDA. 



We have placed the Tardigrada and the Pentastomida in 

 appendices to the group Arachnida because they show distinct 

 Arthropod characters and their affinities point more closely to 

 the Arachnida than to any other group of Arthropods. 



Order TARDIGRADA. 



Minute, cryptozoic animals with four pairs of stumpy clawed legs, 

 suctorial mouth and oral armature, without circulatory and 

 respiratory systems and connective tissue. 



The Tardigrada are cryptozoic, living a retired life amongst 

 moss and debris collected in gutters, of roofs, on tree- trunks f 



* Nalepa, Das Tierreich, 4 Lieferung, Eriophyidae (Phytoptidae). 



t Plate, Zool. Jahrb. Anat., iii, 1889. v. Erlanger, 1895, Morph. 

 Jahrb., xxii, 1895. Richters, Zool. Anz., xxxi, 1907, p. 197. and Heinis, 

 Zool. Anz., xxxii., 1908, p. 633. 



