440 
it  is  found  also  in  other  natural  cavities  of  these  animals.  Colonies 
of  this  tick  were  found  altogether  on  eighteen  horses  ;  and  two  or 
three  isolated  examples  occurred  also  on  the  ox  and  dog. 
SILVER  TICK 
Amblyomma  cajanense  (Fab.). 
Engorged  or  replete  female.  Surface  of  skin  not  highly  polished. 
Dull  bluish  grey,  with  dark  purplish  brown  reticulations.  The  ground 
colour  appearing  as  pale  round  spots  on  the  lower  half  of  the  body 
where  the  brown  colour  predominates ;  excretory  system  showing 
through  the  cuticle  as  pale  dull  yellow  markings ;  but  there  is  usually 
a  more  or  less  well-defined  patch  of  yellow,  often  somewhat 
rectangular  in  form  just  behind  the  scutum  from  which  the  branched 
markings  diverge.  Ventral  surface  pale  bluish  grey  with  irregular 
whitish  markings.  Mouth  parts  {capituhui'i)  pale  brown,  usually  with 
two  minute  dark  spots  at  the  posterior  lateral  angles.  Scutum, 
faintly  metallic,  with  two  dark  brown  submedian  curved  lines ;  lateral 
margin,  dark  brown  behind  the  eyes,  terminating  before  the  apex, 
the  latter  pale  golden-yellow.  Eyes  pale,  almost  colourless.  Legs 
pale  brown ;  segmentation  paler,  appearing  as  very  faint  rings. 
Length  lo  to  I2'2  5  mm. 
U nengor ged  female.  Similar  in  size  to  the  male  but  is  easily 
recognised  by  the  small  shield  (scutum)  on  the  back.  It  is  also  less 
brilliantly  coloured  than  the  male ;  and  the  marginal  festoons  are 
either  entirely  absent  or  scarcely  visible  to  the  unaided  eye.  Length 
5  to  6  mm. 
Male.  Pale  dull  yellow  or  brownish  yellow,  with  irregular  silvery 
white  markings  or  streaks  and  brown  or  red-brown  spots,  forming  a 
definite  but  complex  pattern  which  gives  the  dorsal  surface  (scutum) 
a  somewhat  reticulated  appearance,  though  when  seen  under  a  lens  the 
spots  and  streaks  do  not  coalesce.  Length  4  mm. 
Habits.  As  already  stated  this  tick  requires  three  hosts  during 
its  developmental  cycle.  The  first  host  in  its  larval  or  ‘  grass  louse  ’ 
stage,  the  second  in  its  nymphal  or  second  stage,  and  the  third  and  last 
host  in  its  adult  stages.  The  replete  or  fully  engorged  female  (PI.  XIII, 
fig.  i)  lays  her  eggs  on  the  ground  ;  these  produce  larvae  or  ‘grass 
lice,’  which  congregate  together  at  the  tips  of  grass  and  leaves,  or 
