﻿264 
  E. 
  RAY 
  LANKESTliE. 
  

  

  of 
  tlie 
  Cryptostigmata. 
  Tracliea3 
  opening 
  by 
  a 
  pair 
  of 
  stigmata 
  

   situated 
  above 
  and 
  behind 
  the 
  base 
  of 
  the 
  fourth 
  or 
  fifth 
  or 
  

   sixth 
  pair 
  of 
  appendages. 
  

  

  Families 
  : 
  Gamasidte 
  (Gamasus, 
  Pteroptus). 
  

   Argasidas 
  (Argas^ 
  Ornithodoros). 
  

   Ixodidae 
  (Ixodes^ 
  Khipicephalus). 
  

   Sub-order 
  d. 
  Prostigmata. 
  — 
  Integument 
  soft, 
  strength- 
  

   ened 
  by 
  special 
  sclerites, 
  those 
  on 
  the 
  ventral 
  surface 
  of 
  the 
  

   prosoma 
  apparently 
  representing 
  the 
  basal 
  segments 
  of 
  the 
  

   legs 
  imbedded 
  in 
  the 
  skin. 
  TrachesS; 
  except 
  in 
  the 
  aquatic 
  

   species 
  in 
  which 
  they 
  are 
  atrophied, 
  opening 
  by 
  a 
  pair 
  of 
  

   stigmata 
  situated 
  close 
  to 
  or 
  above 
  the 
  base 
  of 
  the 
  appendages 
  

   of 
  the 
  first 
  pair 
  (cheliceras). 
  

  

  Families 
  : 
  Trombidiidae 
  ( 
  T 
  r 
  o 
  m 
  b 
  i 
  d 
  i 
  u 
  m, 
  T 
  e 
  t 
  r 
  a 
  u 
  y 
  c 
  h 
  u 
  s) 
  . 
  

   Hydrachnidge 
  (Hydrachna, 
  Atax). 
  

   Halacaridee 
  (Halacarus, 
  Leptognathus). 
  

   Bdellida? 
  (Bdella, 
  Eupodes). 
  

   Sub-order 
  e. 
  Astigmata. 
  — 
  Degenerate, 
  mostly 
  parasitic 
  

   forms 
  approaching 
  the 
  Prostigmata 
  in 
  the 
  development 
  of 
  

   integumental 
  sclerites 
  and 
  the 
  softness 
  of 
  the 
  skin, 
  but 
  with 
  

   the 
  respiratory 
  system 
  absent. 
  

  

  Families: 
  Tyroglyphid^e 
  (Tyroglyphus, 
  Khizoglyphus). 
  

   Sarcoptidte 
  (Sarcoptes, 
  Analges). 
  

   Sub-order 
  /. 
  V 
  e 
  r 
  mi 
  f 
  o 
  r 
  m 
  i 
  a. 
  — 
  Degenerate 
  atracheate 
  para- 
  

   sitic 
  forms 
  with 
  the 
  body 
  produced 
  posteriorly 
  into 
  an 
  annu- 
  

   lated 
  caudal 
  prolongation, 
  and 
  with 
  the 
  third, 
  fourth, 
  fifth, 
  

   and 
  sixth 
  pairs 
  of 
  appendages 
  short 
  and 
  only 
  three-jointed. 
  

   Family 
  Deniodicidas 
  (Demodex). 
  

   Sub-order 
  y. 
  Tetrapoda. 
  — 
  Degenerate 
  atracheate 
  gall- 
  

   mites, 
  in 
  which 
  the 
  body 
  is 
  produced 
  posteriorly 
  and 
  anuulated, 
  

   as 
  in 
  Demodex, 
  but 
  in 
  which 
  the 
  appendages 
  of 
  the 
  third 
  

   and 
  fourth 
  pairs 
  are 
  long 
  and 
  normally 
  segmented, 
  and 
  those 
  

   of 
  the 
  fifth 
  and 
  sixth 
  pairs 
  entirely 
  absent. 
  

  

  Family 
  Eriophyida^ 
  (Eriophyes, 
  Pliy 
  llocoptes). 
  

   Remarks 
  on 
  the 
  Rhynchostomi. 
  — 
  The 
  Acari 
  include 
  

   a 
  number 
  of 
  forms 
  which 
  are 
  of 
  importance 
  and 
  special 
  

   interest 
  on 
  account 
  of 
  their 
  parasitic 
  habits. 
  The 
  ticks 
  

  

  