ORDER TRACHEARIiE. 507 



Ixodes ricinus, Acarus Ricinus, Lin. ; Acarus 7'eduvius, 

 D. G. Insect. VII. vi. 1, 2. : of a deep blood-red, with the 

 anterior scaly plate deeper, sides of the body edged, a little 

 hairy palpi sheathing the sucker. 



Ixodes reticulahis, Latr., Fab. ; Acarus reduvius, Schrank. 

 Enum. Insect. Aust. No. 1043, iii. I, 2 ; Cynorhoestes pictus, 

 Hermn. : ash-coloured, with small spots, and small annular 

 lines of a reddish brown ; edges of the abdomen striated ; 

 palpi almost oval. It attaches itself to oxen, and is, when 

 swelled up, five or six lines in length. 



The study of the species of this genus has not been suffi- 

 ciently pursued. 



Argas, Lat. Rhyncoprion, Herm., 



Differ from Ixodes by the inferior situation of the mouth, and 

 by the palpi, which do not sheath the sucker ; have a conical 

 form, and are composed of four articulations, and not of three, 

 as in the preceding genus. 



Ixodes rejlexiis, Fab., Lat., Gen., Cmst., et insect, &c. 

 Of a pale yellowish, with lines of a deep blood-colour, or 

 obscure and anastomosed. On pigeons, whose blood it sucks. 



Another species, Argas perricus, described by travellers, 

 under the name of the venomous bug of Miana, has been, as 

 well as other ixodes, the object of a curious notice, by M. 

 Fischer. 



Other Mites, HYDRACHNELLiE, have still eight feet, but 

 ciliate, and adapted for swimming. 



They form the genus Hydrachna of Muller, or Athax of 

 Fabricius, and live exclusively in the water. Their body is 

 generally oval, almost globular, and very soft. That of some 

 males is narrowed posteriorly, in a cylindrical manner, or in 

 the form of a tail. Their genital parts are placed at its ex- 

 tremity ; the female has them under the belly. The number 



