﻿ACARI 
  OCCURRING 
  ON 
  THE 
  BROWN 
  RAT 
  IN 
  GREAT 
  BRITAIN. 
  121 
  

  

  Laelaps 
  echidninus 
  is 
  a 
  true 
  blood-sucking 
  parasite. 
  It 
  is 
  easy 
  to 
  demonstrate 
  the 
  

   presence 
  of 
  ingested 
  blood 
  of 
  the 
  host 
  in 
  the 
  mite 
  by 
  teasing 
  up 
  freshly 
  caught 
  female 
  

   specimens 
  or 
  making 
  smear 
  preparations 
  of 
  them, 
  when 
  large 
  numbers 
  of 
  unaltered 
  

   blood 
  corpuscles 
  will 
  be 
  seen. 
  

  

  Mr. 
  A. 
  Bacot, 
  of 
  the 
  Lister 
  Institute 
  of 
  Preventive 
  Medicine, 
  and 
  myself 
  have 
  made 
  

   a 
  series 
  of 
  experiments 
  with 
  a 
  view 
  to 
  ascertaining 
  whether 
  L. 
  echidninus 
  is 
  capable 
  

   of 
  conveying 
  plague 
  from 
  rat 
  to 
  rat 
  or 
  not. 
  Unfortunately, 
  we 
  could 
  not 
  get 
  good 
  

   plague 
  septicaemia 
  in 
  rats, 
  and 
  our 
  experiments 
  were 
  therefore 
  quite 
  inconclusive. 
  

   Mice 
  develop 
  good 
  plague 
  septicaemia, 
  but 
  L. 
  echidninus 
  will 
  not 
  bite 
  mice 
  readily, 
  

   hence 
  our 
  experiments 
  with 
  Mus 
  musculus 
  also 
  had 
  to 
  be 
  abandoned. 
  The 
  mite 
  

   could 
  not 
  be 
  induced 
  to 
  bite 
  human 
  beings. 
  It 
  may 
  be 
  of 
  interest 
  to 
  note 
  that 
  

   a 
  bipolar 
  staining 
  bacillus 
  very 
  closely 
  resembling 
  the 
  plague 
  bacillus 
  sometimes 
  

   occurs 
  in 
  smear 
  preparations 
  of 
  L. 
  echidninus 
  bred 
  on 
  apparently 
  perfectly 
  healthy 
  

   rats. 
  

  

  (2.) 
  Eulaelaps 
  stabularis, 
  C. 
  L. 
  Koch. 
  

  

  Loc. 
  We 
  have 
  specimens 
  of 
  this 
  species 
  captured 
  on 
  Mus 
  norvegicus 
  at 
  the 
  following 
  

   localities 
  : 
  — 
  Northwood, 
  Middlesex, 
  4. 
  x. 
  1913 
  ; 
  one 
  specimen. 
  Banks 
  of 
  River 
  

   Thames, 
  between 
  Hampton 
  and 
  Kingston, 
  8. 
  ix. 
  1913 
  ; 
  thirty-five 
  specimens. 
  

   Clachan, 
  Argyleshire, 
  Scotland, 
  25. 
  xi. 
  1909 
  ; 
  one 
  specimen 
  (W 
  aterston). 
  

  

  (3). 
  Hypoaspis 
  hypudaei, 
  Oudms. 
  

  

  Loc. 
  Northwood, 
  Middlesex 
  ; 
  a 
  few 
  specimens 
  found 
  on 
  Mus 
  norvegicus, 
  x. 
  1913. 
  

   Banks 
  of 
  River 
  Thames, 
  between 
  Hampton 
  and 
  Kingston 
  ; 
  thirty 
  specimens 
  found 
  

   on 
  Mus 
  norvegicus. 
  

  

  (4.) 
  Haemogamasus 
  hirsutus, 
  Berl. 
  

  

  Loc. 
  Northwood, 
  Middlesex 
  ; 
  a 
  single 
  male 
  specimen 
  from 
  M 
  us 
  norvegicus. 
  

  

  (5.) 
  Haemogamasus 
  nidi, 
  Mich. 
  (PL 
  XVI, 
  fig. 
  8). 
  

  

  Haemogamasus 
  nidi, 
  Michael, 
  Trans. 
  Linn. 
  Soc. 
  Zool. 
  (2) 
  v, 
  p. 
  314 
  & 
  315, 
  pi. 
  32, 
  

   figs. 
  6 
  & 
  7 
  (1892). 
  

  

  Haemogamasus 
  michaeli, 
  Oudemans, 
  Tijdschr. 
  Nederland. 
  Dierk. 
  Ver. 
  (2) 
  viii, 
  

   pp. 
  87 
  & 
  88, 
  pi. 
  6, 
  figs. 
  33-39 
  (1904); 
  Oudemans, 
  Arch. 
  Naturg. 
  Berlin, 
  

   Abt. 
  A, 
  heft 
  8, 
  pp. 
  155-160, 
  figs. 
  108-140 
  (1913). 
  

  

  2. 
  Sternal 
  plate 
  not 
  much 
  shorter 
  in 
  the 
  middle 
  than 
  at 
  the 
  sides, 
  but 
  furnished 
  with 
  

   only 
  three 
  pairs 
  of 
  hairs, 
  as 
  in 
  H. 
  oudemansi. 
  Genito- 
  ventral 
  plate 
  somewhat 
  enlarged 
  

   and 
  rounded 
  posteriorly 
  ; 
  the 
  hairs 
  on 
  its 
  surface 
  are 
  somewhat 
  shorter 
  and 
  very 
  

   much 
  more 
  numerous 
  than 
  is 
  the 
  case 
  in 
  H. 
  oudemansi. 
  Anal 
  plate 
  furnished 
  with 
  

   7-9 
  hairs. 
  

  

  cJ. 
  Chelicera. 
  Immovable 
  finger 
  rather 
  gradually 
  curved 
  and 
  the 
  end 
  pointed, 
  but 
  

   not 
  abruptly 
  turned 
  down 
  ; 
  it 
  has 
  a 
  transparent 
  lamina 
  instead 
  of 
  a 
  hair. 
  Movable 
  

   finger 
  very 
  strongly 
  curved 
  (claw-like) 
  and 
  sharply 
  pointed. 
  For 
  the 
  shape 
  of 
  its 
  

   appendage 
  see 
  PL 
  XVI, 
  fig. 
  8. 
  

  

  Loc. 
  Northwood, 
  Middlesex 
  ; 
  a 
  large 
  number 
  of 
  specimens 
  taken 
  at 
  different 
  times 
  

   on 
  Mus 
  norvegicus, 
  mostly 
  in 
  October 
  1913. 
  Clachan, 
  Argyleshire, 
  Scotland 
  ; 
  three 
  

   specimens 
  taken 
  on 
  Mus 
  norvegicus, 
  25. 
  xi. 
  1909 
  (W 
  aterston). 
  Lochgelly, 
  Fife, 
  

   Scotland 
  ; 
  two 
  specimens 
  from 
  M. 
  norvegicus, 
  21. 
  x. 
  1909. 
  We 
  have 
  also 
  a 
  specimen 
  

  

  