﻿198 
  W. 
  A. 
  LAMBORN. 
  — 
  THE 
  AGRICULTURAL 
  PESTS 
  

  

  Colonies 
  of 
  the 
  cotton 
  aphis, 
  Aphis 
  gossypii, 
  Glov., 
  which 
  produce 
  a 
  characteristic 
  

   wrinkling 
  and 
  infolding 
  of 
  the 
  margins 
  of 
  the 
  young 
  leaves, 
  were 
  abundant 
  early 
  in 
  

   the 
  season 
  (August), 
  but 
  were 
  soon 
  thoroughly 
  checked 
  by 
  natural 
  enemies, 
  the 
  chief 
  

   of 
  which 
  were 
  found 
  to 
  be 
  Coccinellid 
  beetles, 
  Chilomenes 
  lunata, 
  F., 
  Chilomenes 
  

   vicina, 
  Muls., 
  and 
  Hyperaspis 
  pumila, 
  Muls., 
  all 
  of 
  which 
  preyed, 
  both 
  as 
  larvae 
  and 
  

   imagos, 
  on 
  the 
  aphids. 
  The 
  larvae 
  of 
  three 
  species 
  of 
  Syrphid 
  flies, 
  Syrphus 
  nasutus, 
  

   Wied., 
  Paragus 
  borbonicus, 
  Mcq., 
  and 
  P. 
  longiventris, 
  Bezzi, 
  and 
  the 
  larva 
  of 
  a 
  lace- 
  

   wing, 
  Micromus 
  timidus, 
  Hagen, 
  also 
  ate 
  them 
  voraciously. 
  By 
  far 
  the 
  worst 
  pest 
  

   feeding 
  on 
  cotton 
  leaf 
  was 
  the 
  short-horned 
  grasshopper, 
  Zonocerus 
  variegatus, 
  L. 
  

   Immense 
  swarms 
  of 
  nymphs 
  appeared 
  suddenly, 
  all 
  about 
  the 
  same 
  time 
  in 
  November, 
  

   and 
  entirely 
  defoliated 
  numerous 
  plants. 
  But 
  though 
  cotton 
  appeared 
  to 
  be 
  the 
  

   favourite 
  food, 
  the 
  pests 
  were 
  practically 
  omnivorous 
  and 
  attacked, 
  in 
  addition 
  to 
  

   a 
  large 
  variety 
  of 
  wild 
  plants, 
  other 
  plants 
  under 
  cultivation, 
  young 
  maize, 
  young 
  

   Para 
  rubber, 
  cassava 
  in 
  particular 
  (Plate 
  xix), 
  bananas, 
  and 
  a 
  variety 
  of 
  ornamental 
  

   plants, 
  especially 
  Acalypha. 
  Cacao 
  was 
  occasionally 
  attacked, 
  but 
  fortunately 
  

   was 
  not 
  a 
  favourite 
  food. 
  

  

  The 
  insects 
  gradually 
  scattered 
  as 
  they 
  attained 
  maturity, 
  and 
  in 
  late 
  January 
  

   completed 
  the 
  last 
  ecdysis 
  (Plate 
  xxv, 
  fig. 
  2), 
  after 
  which 
  they 
  were 
  to 
  be 
  seen 
  in 
  

   coitu 
  everywhere, 
  and 
  shortly 
  afterwards 
  new 
  swarms 
  of 
  larvae 
  appeared. 
  

  

  The 
  multiplicity 
  of 
  food-plants 
  and 
  the 
  enormous 
  numbers 
  of 
  the 
  pest 
  made 
  the 
  

   question 
  of 
  dealing 
  with 
  them 
  a 
  difficult 
  one 
  ; 
  moreover 
  it 
  was 
  felt 
  that 
  the 
  use 
  of 
  

   Paris 
  green, 
  whether 
  as 
  a 
  spray 
  or 
  as 
  a 
  dusting 
  powder, 
  was 
  undesirable 
  from 
  the 
  

   ginners 
  point 
  of 
  view. 
  Chromate 
  of 
  lead, 
  prepared 
  as 
  recommended 
  by 
  Lefroy, 
  

   was 
  therefore 
  used 
  in 
  spray 
  form 
  as 
  the 
  lesser 
  evil 
  and 
  it 
  certainly 
  had 
  a 
  deterrent 
  

   effect, 
  causing 
  the 
  majority 
  of 
  the 
  insects 
  to 
  migrate 
  to 
  new 
  feeding 
  grounds 
  and 
  killing 
  

   a 
  few. 
  Since 
  the 
  insects 
  are 
  gregarious 
  through 
  the 
  greater 
  part 
  of 
  the 
  fife-cycle, 
  it 
  

   is 
  possible 
  that 
  a 
  trial 
  of 
  d'Herelle's 
  virus 
  might 
  have 
  yielded 
  valuable 
  results, 
  but 
  

   a 
  supply 
  could 
  not 
  be 
  obtained 
  in 
  time 
  for 
  that 
  season. 
  

  

  The 
  leaf 
  -roller, 
  Sylepta 
  derogata, 
  F., 
  occurred 
  abundantly 
  early 
  in 
  the 
  season, 
  about 
  

   November, 
  on 
  certain 
  imported 
  varieties, 
  American 
  Upland 
  in 
  particular, 
  but 
  were 
  

   much 
  less 
  numerous 
  on 
  the 
  native 
  cottons, 
  the 
  so-called 
  Ishan 
  and 
  Meko 
  varieties. 
  

   Tachinid 
  parasites, 
  possibly 
  of 
  two 
  species, 
  an 
  Ichneumonid, 
  Xanthopimpla 
  punctata, 
  

   F., 
  and 
  some 
  Braconidae 
  were 
  bred 
  out 
  from 
  the 
  pupae, 
  but 
  were 
  not 
  numerous 
  

   enough 
  to 
  be 
  effective 
  in 
  checking 
  the 
  pest. 
  An 
  attempt 
  was 
  therefore 
  made 
  to 
  cope 
  

   with 
  it 
  by 
  the 
  use 
  of 
  insecticidal 
  sprays, 
  which 
  did 
  not 
  however 
  prove 
  a 
  success, 
  owing 
  

   to 
  the 
  difficulty 
  of 
  getting 
  the 
  poison 
  on 
  to 
  the 
  rolled- 
  up 
  part 
  of 
  the 
  leaf, 
  on 
  which 
  the 
  

   caterpillar 
  mainly 
  subsists. 
  Kesort 
  was 
  therefore 
  had 
  to 
  hand-picking 
  by 
  small 
  

   native 
  boys, 
  who 
  collected 
  at 
  the 
  same 
  time 
  the 
  various 
  cotton 
  stainers. 
  

  

  The 
  larvae 
  of 
  the 
  Limacod 
  moth, 
  Parasa 
  infuscata, 
  Wichg., 
  were 
  not 
  uncommon, 
  

   and 
  green 
  half-looper 
  Noctuid 
  larvae 
  were 
  found 
  from 
  time 
  to 
  time, 
  but 
  were 
  not 
  

   responsible 
  for 
  any 
  great 
  damage, 
  being 
  kept 
  down 
  by 
  the 
  agency 
  of 
  a 
  species 
  of 
  

   Eumenid 
  wasp, 
  Eumenes 
  maxillosa, 
  de 
  Geer, 
  a 
  black 
  household 
  insect 
  very 
  common 
  

   in 
  the 
  Ibadan 
  district, 
  which 
  stored 
  the 
  larvae 
  as 
  food 
  for 
  its 
  grubs 
  in 
  great 
  numbers, 
  

   five 
  or 
  six 
  being 
  often 
  found 
  in 
  each 
  of 
  the 
  seven 
  or 
  eight 
  cells 
  composing 
  its 
  nest. 
  

  

  Various 
  beetles, 
  a 
  Lagriid, 
  Lagria 
  villosa, 
  F., 
  and 
  the 
  Eumolpid 
  Syagrus 
  calcaratus, 
  

   F., 
  in 
  particular, 
  were 
  found 
  to 
  cause 
  a 
  certain 
  amount 
  of 
  leaf 
  damage. 
  

  

  