﻿PREVALENCE 
  OF 
  LOCUSTS 
  IN 
  DRY 
  REGIONS. 
  55 
  

  

  or 
  vast 
  treeless 
  areas, 
  and 
  an 
  arid 
  or 
  dry 
  climate. 
  The 
  desert 
  character 
  

   of 
  that 
  vast 
  region 
  of 
  Northern 
  Africa 
  extending 
  from 
  Senegal 
  to 
  the 
  

   Mediterranean, 
  and 
  from 
  the 
  Atlantic 
  to 
  the 
  Eed 
  Sea, 
  is 
  well 
  known, 
  as 
  

   is 
  also 
  the 
  arid 
  and 
  desert 
  character 
  of 
  a 
  large 
  part 
  of 
  Arabia, 
  Syria, 
  

   Persia, 
  and 
  Mesopotamia. 
  The 
  Ukraine, 
  Crimea, 
  and 
  the 
  regions 
  around 
  

   the 
  north 
  and 
  east 
  of 
  the 
  Caspian 
  Sea, 
  are 
  characterized 
  by 
  those 
  broad, 
  

   treeless, 
  and 
  more 
  or 
  less 
  elevated 
  plains 
  to 
  which 
  the 
  name 
  steppes 
  has 
  

   been 
  applied. 
  Extensive 
  pampas 
  and 
  treeless 
  plains 
  form 
  a 
  marked 
  

   feature 
  of 
  those 
  sections 
  of 
  South 
  America 
  in 
  which 
  the 
  locusts 
  are 
  

   found. 
  The 
  same 
  we 
  know 
  also 
  to 
  be 
  true 
  in 
  reference 
  to 
  the 
  locust 
  

   districts 
  in 
  North 
  America. 
  Keferstein 
  remarks 
  148 
  that 
  high 
  chains 
  of 
  

   mountains 
  covered 
  with 
  snow 
  are 
  the 
  best 
  natural 
  barriers 
  against 
  the 
  

   extension 
  and 
  migrations 
  of 
  the 
  destructive 
  locusts. 
  That 
  this 
  may 
  be 
  

   true 
  when 
  applied 
  to 
  some 
  species 
  is 
  not 
  to 
  be 
  doubted, 
  but 
  that 
  it 
  is 
  

   applicable 
  to 
  all 
  is 
  disputed 
  by 
  the 
  history 
  of 
  our 
  native 
  species, 
  G. 
  spretus. 
  

   Bitter 
  assures 
  us 
  149 
  that 
  no 
  traces 
  of 
  locusts 
  are 
  found 
  in 
  the 
  cold 
  climate 
  

   of 
  Thibet, 
  in 
  cool 
  Cashmere, 
  and 
  that 
  in 
  the 
  central 
  interior 
  of 
  Asia, 
  be- 
  

   tween 
  the 
  Himalaya 
  and 
  Altai 
  mountain 
  systems, 
  and 
  on 
  the 
  plains 
  of 
  

   Dekkan, 
  in 
  the 
  south 
  of 
  Nerbudda, 
  or 
  in 
  India 
  beyond 
  the 
  Ganges, 
  be- 
  

   tween 
  the 
  Brahmapootra 
  and 
  Irawaddy 
  Eivers 
  and 
  Tangtse-Kiang, 
  

   where 
  a 
  misty, 
  rainy, 
  maritime 
  climate 
  prevails, 
  the 
  locust 
  plague 
  is 
  un- 
  

   known. 
  150 
  

  

  Judging 
  from 
  the 
  silence 
  of 
  Stanley, 
  Schweinfurt, 
  and 
  some 
  other 
  recent 
  

   travelers 
  in 
  reference 
  to 
  locusts, 
  there 
  is 
  a 
  large 
  region 
  in 
  Central 
  Africa 
  

   in 
  which 
  they 
  do 
  not 
  prevail. 
  The 
  same 
  appears 
  to 
  be 
  true 
  in 
  regard 
  to 
  

   a 
  large 
  part 
  of 
  the 
  northern 
  portion 
  of 
  South 
  America, 
  where 
  a 
  rich 
  and 
  

   luxuriant 
  growth 
  of 
  vegetation 
  and 
  a 
  moist 
  climate 
  prevail. 
  The 
  free- 
  

   dom 
  of 
  Eastern 
  North 
  American 
  from 
  this 
  pest 
  is 
  well 
  known. 
  

  

  A 
  third 
  important 
  conclusion 
  to 
  be 
  drawn 
  from 
  our 
  brief 
  review 
  is 
  

   that 
  locust 
  migrations 
  are 
  not 
  governed 
  by 
  any 
  law 
  of 
  regular 
  peri- 
  

   odicity. 
  If 
  we 
  divide 
  the 
  number 
  of 
  years 
  given 
  by 
  the 
  Chinese 
  rec- 
  

   ord 
  (1,924) 
  by 
  the 
  number 
  of 
  visitations 
  (173) 
  it 
  gives 
  an 
  average 
  of 
  

   a 
  little 
  over 
  11 
  years. 
  The 
  time 
  embraced 
  in 
  Kcerte's 
  list 
  of 
  the 
  30 
  inva- 
  

   sions 
  of 
  Germany 
  also 
  gives 
  an 
  average 
  of 
  a 
  little 
  over 
  11 
  years. 
  Kop- 
  

   pen's 
  list 
  of 
  the 
  visitations 
  of 
  Eussia 
  and 
  adjoining 
  regions 
  151 
  from 
  1008 
  to 
  

   1861 
  gives 
  an 
  average 
  interim 
  of 
  something 
  over 
  13 
  years. 
  Although 
  

   the 
  average 
  periods 
  thus 
  obtained 
  by 
  dividing 
  the 
  whole 
  number 
  of 
  

   years 
  by 
  the 
  number 
  of 
  visitations 
  agree 
  so 
  nearly, 
  yet 
  by 
  simply 
  run- 
  

   ning 
  the 
  eye 
  over 
  the 
  lists 
  of 
  years 
  any 
  one 
  can 
  see 
  that 
  this 
  argument 
  

   is 
  purely 
  accidental 
  and 
  will 
  not 
  hold 
  good 
  when 
  applied 
  to 
  the 
  various 
  

   interims. 
  In 
  the 
  earlier 
  times 
  less 
  attention 
  was 
  paid 
  not 
  only 
  to 
  the 
  

   study 
  of 
  natural 
  history 
  but 
  to 
  agriculture 
  than 
  at 
  present, 
  and 
  only 
  the 
  

  

  ^L.c. 
  

  

  U9 
  Heu8chreck:enplage 
  der 
  Alten 
  Welt, 
  p. 
  7. 
  

  

  160 
  But 
  see 
  statement 
  of 
  Colonel 
  Prej 
  valsty, 
  G 
  eoa 
  Mag., 
  May, 
  1878, 
  quoted 
  in 
  our 
  former 
  Eeport, 
  p. 
  477, 
  

   that 
  swarms 
  of 
  locusts 
  were 
  seen 
  at 
  an 
  elevatioi 
  > 
  • 
  1,000 
  feet 
  in 
  Altyn-Tag 
  range, 
  in 
  Central 
  Asia- 
  

   151 
  " 
  Heuschrecken 
  in 
  Sudrussland," 
  pp. 
  110-12 
  . 
  

  

  