﻿224 
  

  

  in 
  one 
  night 
  the 
  most 
  beautiful 
  field, 
  garden 
  or 
  fruit 
  trees 
  may 
  be 
  

   devastated 
  by 
  a 
  band 
  of 
  leaf-cutting 
  ants, 
  known 
  in 
  the 
  colony 
  under 
  

   the 
  name 
  of 
  '' 
  fourmi-manioc," 
  the 
  greatest 
  enemy 
  to 
  agriculture 
  in 
  

   Guiana. 
  When 
  on 
  an 
  expedition 
  the 
  ants 
  form 
  two 
  groups 
  ; 
  one 
  

   group 
  climbs 
  the 
  tree 
  and 
  bites 
  off 
  the 
  whole 
  leaf 
  or 
  parts 
  of 
  it, 
  while 
  

   the 
  other 
  group 
  waits 
  at 
  the 
  foot 
  of 
  the 
  tree 
  and 
  gathers 
  the 
  leaves, 
  

   which 
  they 
  carry 
  to 
  the 
  nest. 
  Numerous 
  remedies 
  have 
  been 
  tried 
  

   against 
  these 
  insects 
  without 
  much 
  success, 
  such 
  as 
  the 
  introduction 
  

   into 
  their 
  nests 
  of 
  boiling 
  oil, 
  chloroform, 
  corrosive 
  sublimate, 
  etc., 
  

   and 
  the 
  Clayton 
  system 
  of 
  forcing 
  sulphurous 
  fumes 
  into 
  the 
  nest 
  

   has 
  not 
  proved 
  effective. 
  Carbon 
  bisulphide 
  however 
  has 
  given 
  

   excellent 
  results, 
  but 
  apart 
  from 
  its 
  dangerous 
  qualities, 
  it 
  has 
  the 
  

   drawback 
  of 
  being 
  expensive, 
  as 
  large 
  quantities 
  have 
  to 
  be 
  used. 
  

  

  As 
  a 
  result 
  of 
  his 
  experiments 
  the 
  author 
  w^as 
  led 
  to 
  believe 
  that 
  

   sulphurous 
  anhydride 
  would 
  be 
  still 
  more 
  useful. 
  This 
  substance 
  

   when 
  liquified 
  possesses 
  a 
  considerable 
  force 
  of 
  expansion, 
  w^hich, 
  

   together 
  with 
  its 
  great 
  density, 
  ought 
  to 
  allow 
  it 
  to 
  penetrate 
  to 
  the 
  

   deepest 
  galleries. 
  It 
  is 
  also 
  very 
  soluble 
  in 
  water 
  and 
  diffusible, 
  and 
  

   is 
  not 
  poisonous 
  in 
  small 
  quantities, 
  since 
  the 
  State 
  authorises 
  its 
  use 
  

   in 
  wine-making 
  to 
  the 
  extent 
  of 
  350 
  milligrams 
  per 
  litre. 
  The 
  air 
  

   cannot 
  be 
  breathed 
  when 
  it 
  contains 
  1'5 
  per 
  cent, 
  of 
  this 
  gas. 
  Pure 
  

   liquefied 
  sulphurous 
  anhydride 
  is 
  prepared 
  by 
  two 
  companies 
  in 
  

   Paris 
  — 
  La 
  Compagnie 
  Paoul 
  Pictet, 
  and 
  Le 
  Laboratoire 
  des 
  Industries 
  

   AHmentaires. 
  In 
  Guiana 
  this 
  substance 
  may 
  be 
  obtained 
  for 
  0'85 
  

   francs 
  (about 
  8d.) 
  per 
  kilo. 
  (2'2 
  lb.), 
  and 
  is 
  sent 
  in 
  copper 
  or 
  steel 
  drums 
  

   containing 
  25, 
  50 
  or 
  100 
  kilos. 
  These 
  drums 
  are 
  stamped 
  at 
  30 
  

   atmospheres 
  and 
  have 
  a 
  tap. 
  This 
  tap 
  is 
  prolonged 
  to 
  the 
  interior 
  

   so 
  as 
  to 
  receive 
  a 
  bent 
  tube 
  forming 
  a 
  siphon, 
  so 
  arranged 
  that 
  according 
  

   to 
  the 
  position 
  in 
  which 
  the 
  drum 
  is 
  placed 
  the 
  anhydride 
  can 
  be 
  

   obtained 
  either 
  as 
  a 
  gas 
  or 
  a 
  liquid. 
  Having 
  obtained 
  one 
  of 
  these 
  

   drums, 
  it 
  is 
  placed 
  near 
  the 
  nest 
  about 
  to 
  be 
  destroyed, 
  and 
  a 
  tube 
  

   3 
  metres 
  long 
  and 
  1 
  centimetre 
  in 
  diameter 
  is 
  attached 
  to 
  it, 
  by 
  means 
  

   of 
  a 
  union. 
  This 
  tube 
  is 
  flexible, 
  being 
  made 
  of 
  bronze 
  and 
  asbestos, 
  

   and 
  surrounded 
  by 
  a 
  metal 
  twist 
  of 
  bronze 
  to 
  make 
  it 
  stronger. 
  It 
  

   ends 
  in 
  a 
  stiff 
  copper 
  spike 
  about 
  75 
  centimetres 
  long, 
  pierced 
  in 
  the 
  

   last 
  ten 
  centimetres 
  with 
  about 
  a 
  dozen 
  holes 
  to 
  allow 
  the 
  gas 
  to 
  escape. 
  

   The 
  outside 
  of 
  the 
  nest 
  is 
  cleared 
  to 
  expose 
  all 
  the 
  openings 
  and 
  it 
  is 
  

   generally 
  necessary 
  to 
  remove 
  the 
  superficial 
  layer 
  of 
  earth. 
  The 
  

   spike 
  is 
  then 
  inserted 
  into 
  a 
  hole 
  only 
  when 
  it 
  can 
  be 
  easily 
  thrust 
  in 
  

   to 
  a 
  depth 
  of 
  20 
  to 
  25 
  centimetres 
  in 
  any 
  one 
  direction, 
  all 
  the 
  openings 
  

   being 
  thus 
  treated. 
  The 
  spike 
  should 
  each 
  time 
  be 
  slipped 
  into 
  a 
  hole 
  

   before 
  opening 
  the 
  tap, 
  the 
  whole 
  process 
  taking 
  about 
  two 
  hours. 
  

   The 
  necessary 
  time 
  for 
  each 
  hole 
  varies, 
  according 
  to 
  its 
  importance 
  

   in 
  the 
  nest, 
  from 
  two 
  to 
  five 
  minutes. 
  After 
  the 
  use 
  of 
  sulphurous 
  

   anhydride 
  it 
  is 
  not 
  at 
  all 
  necessary 
  to 
  dig 
  out 
  the 
  nest, 
  but 
  it 
  should 
  

   be 
  visited 
  a 
  few 
  days 
  later 
  to 
  see 
  whether 
  any 
  ants 
  are 
  still 
  alive. 
  

   This 
  method 
  has 
  been 
  employed 
  with 
  perfect 
  success 
  in 
  the 
  destruction 
  

   of 
  many 
  large 
  nests, 
  and 
  the 
  treatment 
  of 
  a 
  nest 
  15 
  metres 
  in 
  circum- 
  

   ference 
  and 
  the 
  top 
  about 
  40 
  centimetres 
  above 
  the 
  level 
  of 
  the 
  soil, 
  

   was 
  witnessed 
  by 
  a 
  meeting 
  of 
  the 
  Chamber 
  of 
  Agriculture. 
  The 
  

   next 
  day 
  this 
  nest 
  w^as 
  dug 
  out 
  and 
  found 
  to 
  consist 
  of 
  seven 
  tiers 
  of 
  

   nests, 
  the 
  lowest 
  being 
  at 
  a 
  depth 
  of 
  1*5 
  metres; 
  all 
  the 
  ants 
  w^ere 
  

   dead 
  and 
  discoloured, 
  4 
  kilos 
  of 
  sulphurous 
  anhydride 
  being 
  used. 
  

  

  