﻿218 
  

  

  STANLEY 
  HIRST. 
  — 
  ON 
  THE 
  PARASITIC 
  ACARI 
  

  

  behind 
  each 
  of 
  the 
  coxae 
  of 
  the 
  last 
  pair 
  of 
  legs. 
  Peritreme 
  extending 
  forwards 
  as 
  

   far 
  as 
  the 
  middle 
  of 
  the 
  second 
  coxa 
  or 
  slightly 
  further. 
  Anterior 
  surface 
  of 
  coxa 
  

   of 
  second 
  leg 
  with 
  a 
  well-developed 
  spur 
  as 
  in 
  the 
  adult 
  female. 
  Length 
  of 
  body, 
  

   1 
  mm. 
  

  

  Fig. 
  4. 
  Dermanyssus 
  muris, 
  Hirst 
  ; 
  ventral 
  and 
  dorsal 
  aspects 
  of 
  protonymph. 
  

  

  Protonymph. 
  Principal 
  dorsal 
  shield 
  very 
  different 
  in 
  shape 
  from 
  that 
  of 
  the 
  

   female 
  and 
  deutonymph. 
  It 
  is 
  fairly 
  large 
  and 
  rather 
  wide, 
  but 
  has 
  a 
  narrow 
  tail- 
  

   like 
  prolongation 
  posteriorly 
  ; 
  hairs 
  on 
  its 
  surface 
  long, 
  fine 
  and 
  not 
  very 
  numerous. 
  

   Four 
  minute 
  and 
  inconspicuous 
  platelets 
  are 
  present 
  on 
  each 
  side 
  of 
  the 
  tail-like 
  portion 
  

   of 
  it, 
  those 
  of 
  the 
  anterior 
  pair 
  being 
  narrow 
  and 
  elongated, 
  but 
  those 
  of 
  the 
  other 
  

   three 
  pairs 
  much 
  smaller 
  and 
  oval 
  in 
  shape. 
  A 
  rather 
  small 
  but 
  distinct 
  posterior 
  

   dorsal 
  shield, 
  which 
  is 
  transversely 
  elongated 
  and 
  somewhat 
  recurved, 
  is 
  also 
  present 
  

   and 
  bears 
  2-4 
  hairs. 
  A 
  little 
  subcircular 
  platelet 
  is 
  situated 
  on 
  the 
  side 
  of 
  the 
  body 
  

   above 
  the 
  interval 
  between 
  the 
  first 
  and 
  second 
  legs 
  and 
  another 
  very 
  similar, 
  but 
  

   almost 
  ovate, 
  platelet 
  is 
  situated 
  slightly 
  in 
  advance 
  of 
  the 
  anterior 
  end 
  of 
  the 
  peri- 
  

   treme. 
  Sternal 
  plate 
  fairly 
  wide 
  and 
  reaching 
  backwards 
  to 
  about 
  the 
  middle 
  of 
  the 
  

   last 
  coxae 
  ; 
  it 
  has 
  three 
  pairs 
  of 
  long 
  fine 
  hairs 
  on 
  it. 
  There 
  are 
  three 
  pairs 
  of 
  very 
  

   minute 
  and 
  inconspicuous 
  platelets 
  posterior 
  to 
  the 
  sternal 
  plate 
  and 
  a 
  distinct 
  bilobed 
  

   platelet 
  behind 
  each 
  of 
  the 
  last 
  coxae. 
  Peritreme 
  very 
  short. 
  Anterior 
  surface 
  of 
  

   coxa 
  of 
  second 
  leg 
  armed 
  with 
  a 
  small 
  but 
  distinct 
  spur. 
  Length 
  of 
  body, 
  '72 
  mm. 
  

  

  