427 
Judging  by  these  statements  it  is  clearly  evident  that  ticks  are 
most  prevalent  in  dirty  pastures  with  weeds,  scrub  and  trash  about 
them.  On  the  other  hand,  there  is  abundant  evidence  that  clean 
pastures  are  freer  from  these  pests.  We  must  not  lose  sight  of  the 
fact,  however,  that  ‘  grass  lice,’  in  particular,  will  always  be  less  evident 
on  clean  ground  than  on  weedy  or  scrubby  ground,  as  under  the 
former  conditions  they  have  less  opportunity  of  clinging  to  the 
garments  of  any  person  who  may  pass  over  infested  areas.  With  tall 
grass  and  scrub  it  is  different,  because  the  '  grass  lice  ’  climb  to  the 
higher  stems  and  leaves,  and  in  this  way  more  readily  attach  them¬ 
selves  to  man  and  thus  render  themselves  more  conspicuous. 
Shade  and  a  certain  amount  of  moisture  appear,  however,  to  be 
highly  essential  to  the  development  of  cattle  ticks,  and  as  such 
conditions  obtain  to  a  greater  extent  in  dirty  pastures  and  among  tall 
guinea  grass,  there  can  be  little  doubt  that  more  ‘  grass  lice  ’  will  hatch, 
and  possibly  survive  for  longer  periods,  under  such  conditions  than  in 
a  clean  open  pasture  exposed  to  the  full  blaze  of  a  tropical  sun. 
LONGEVITY  OF  TICKS  WITHOUT  ACCESS  TO  A  HOST 
That  various  ticks  are  capable  of  fasting  for  very  long  periods 
has  been  proved  repeatedly  by  many  investigators  in  different  parts 
of  the  world.  In  Jamaica,  however,  nothing  has  been  done  in  regard 
to  this  subject,  and  it  remains  to  be  seen  how  long  the  two  more 
abundant  species  may  survive  without  access  to  a  host.  This  is  a 
most  important  matter,  as  it  materially  affects  the  methods  of  control 
when  dealing  with  tick-infested  land.  For  the  Texas  fever  tick 
{M.  annulatus  australis)  it  is  essential  only  to  test  the  duration  of 
life  in  the  larva.  The  silver  tick  {Ambly omnia  cajanense),  on  the 
other  hand,  presents  a  more  difficult  problem,  as  the  duration  of  life 
without  access  to  a  host  must  be  determined  in  all  three  of  its  stages 
— larva,  nymph  and  adult. 
The  American  authors,  Hunter  and  Hooker,*  proved 
experimentally  that  the  North  American  fever  tick  {Mar  gar  opus 
annulatus),  the  typical  form  of  the  variety  found  in  Jamaica,  can 
survive,  in  its  larval  stage,  without  a  host  for  a  period  varying  from 
49  to  159  days;  and  we  shall  probably  find  that  the  Jamaican 
*  Loc.  cit..  p.  25 
