﻿220 
  

  

  STANLEY 
  HIRST.— 
  ON 
  THE 
  PARASITIC 
  ACARI 
  

  

  practically 
  trapezoidal 
  in 
  shape 
  ; 
  although 
  considerably 
  wider 
  than 
  long, 
  its 
  length 
  

   is 
  much 
  greater 
  as 
  compared 
  with 
  the 
  width 
  than 
  is 
  the 
  case 
  in 
  D. 
  aegyptius 
  ; 
  there 
  

   are 
  three 
  pairs 
  of 
  hairs 
  on 
  its 
  surface. 
  Genito-ventral 
  plate 
  narrow 
  and 
  long, 
  extending 
  

   backwards 
  far 
  beyond 
  the 
  last 
  coxae. 
  There 
  are 
  three 
  inconspicuous 
  platelets 
  on 
  

   each 
  side 
  of 
  this 
  plate, 
  those 
  of 
  the 
  anterior 
  pair 
  being 
  elongated. 
  Anal 
  plate 
  long 
  

   oval 
  in 
  shape, 
  as 
  in 
  D. 
  aegyptius. 
  Two 
  minute 
  platelets 
  are 
  present 
  posterior 
  to 
  

   (and 
  somewhat 
  to 
  the 
  side 
  of) 
  each 
  of 
  the 
  coxae 
  of 
  the 
  fourth 
  legs. 
  Peritreme 
  extend- 
  

   ing 
  as 
  far 
  forwards 
  as 
  or 
  slightly 
  beyond 
  the 
  middle 
  of 
  the 
  coxa 
  of 
  the 
  second 
  leg. 
  

   Anterior 
  surface 
  of 
  coxa 
  of 
  second 
  leg 
  without 
  a 
  spur. 
  Length 
  of 
  body 
  of 
  distended 
  

   specimen, 
  1'4 
  mm. 
  

  

  Fig. 
  6. 
  Dermanyssus 
  sanguineus, 
  Hirst, 
  $ 
  ; 
  ventral 
  and 
  dorsal 
  aspects. 
  

  

  (J. 
  Dorsal 
  shield 
  wide 
  anteriorly 
  but 
  progressively 
  narrowed 
  posteriorly, 
  the 
  

   terminal 
  part 
  of 
  it 
  being 
  quite 
  narrow 
  and 
  the 
  extreme 
  end 
  blunt 
  ; 
  a 
  number 
  of 
  hairs 
  

   of 
  moderate 
  length 
  are 
  present 
  on 
  this 
  shield, 
  including 
  a 
  pair 
  at 
  the 
  posterior 
  end. 
  

   A 
  pair 
  of 
  structures 
  somewhat 
  resembling 
  the 
  eye-like 
  structures 
  of 
  D. 
  muris 
  are 
  

   present 
  in 
  the 
  same 
  position 
  on 
  the 
  dorsal 
  shield, 
  but 
  they- 
  are 
  irregular 
  in 
  shape 
  

   and 
  much 
  less 
  conspicuous. 
  Sterno-ventral 
  plate 
  with 
  the 
  sides 
  not 
  so 
  straight 
  as 
  

   in 
  D. 
  muris, 
  and 
  narrowed 
  so 
  as 
  to 
  form 
  a 
  distinct 
  neck 
  in 
  front 
  of 
  the 
  slightly 
  

  

  