﻿654 
  EEPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  i 
  

  

  de 
  Borre, 
  in 
  the 
  Comptr. 
  Kendus 
  of 
  the 
  Entomological 
  Society 
  of 
  Bel- 
  

   gium, 
  1871-'72, 
  p. 
  xviii 
  : 
  

  

  The 
  migratory 
  locust 
  is 
  an 
  OrlJiopter 
  peculiar 
  to 
  the 
  torrid 
  zone 
  and 
  a 
  large 
  part 
  of 
  

   the 
  north 
  temperate 
  zone 
  of 
  the 
  Old 
  World 
  ; 
  but, 
  in 
  this 
  last 
  region, 
  its 
  northern 
  limits 
  j, 
  

   is 
  subject 
  to 
  some 
  variations, 
  the 
  explanation 
  of 
  which 
  is 
  one 
  of 
  the 
  principal 
  objects 
  ! 
  

   of 
  the 
  work 
  of 
  M. 
  Koppen. 
  

  

  In 
  countries 
  sncli 
  as 
  those 
  of 
  Arabia 
  and 
  Persia, 
  where 
  the 
  mean 
  temperature 
  of 
  the 
  

   year, 
  as 
  that 
  of 
  the 
  different 
  seasons, 
  is 
  almost 
  invariable, 
  the 
  abundance 
  of 
  the 
  species 
  j 
  

   in 
  question 
  does 
  not 
  vary 
  ; 
  it 
  is 
  normally 
  limiled,_both 
  by 
  the 
  quantity 
  of 
  its 
  nourish- 
  \ 
  

   meut 
  and 
  the 
  natural 
  enemies 
  of 
  the 
  insect. 
  But 
  this 
  is 
  not 
  the 
  case 
  in 
  those 
  countries 
  l 
  

   which, 
  like 
  Southern 
  Russia, 
  may 
  present, 
  sometimes 
  favorable 
  seasons, 
  sometimes 
  ,| 
  

   years, 
  or 
  even 
  simply 
  seasons, 
  unfavorable 
  to 
  the 
  multiplication 
  of 
  Pachytylus. 
  Thus, 
  \ 
  

   according 
  to 
  M. 
  Koppen, 
  the 
  persistent 
  prolongation 
  of 
  dry 
  heat 
  during 
  a 
  part 
  of 
  the 
  

   autumn 
  will 
  exert 
  an 
  influence 
  on 
  the 
  quantity 
  of 
  eggs 
  laid 
  in 
  favorable 
  places 
  ; 
  and, 
  

   on 
  the 
  other 
  hand, 
  a 
  temperature 
  less 
  than 
  \hp 
  R^aumer, 
  [6:^° 
  Fahr.,] 
  prolonged 
  for 
  .r, 
  

   several 
  days 
  toward 
  the 
  end 
  of 
  May, 
  will 
  be 
  indispensable 
  to 
  the 
  hatching 
  of 
  the 
  larva. 
  ' 
  

   There 
  would 
  resnlt 
  from 
  the 
  more 
  or 
  less 
  perfect 
  realization 
  of 
  these 
  conditions, 
  and 
  1 
  

   their 
  succession 
  or 
  their 
  interruption 
  during 
  several 
  years, 
  those 
  differences 
  observed 
  J 
  

   in 
  the 
  northern 
  limit 
  of 
  the 
  species, 
  which 
  alternately 
  increase 
  or 
  diminish 
  the 
  area 
  oi 
  ! 
  

   distribution. 
  | 
  

  

  M. 
  Koppen 
  has 
  distinguished 
  and 
  traced 
  quite 
  completely 
  on 
  the 
  map 
  for 
  Europe 
  ^ 
  

   ^and 
  Siberia 
  three 
  different 
  limits 
  of 
  the 
  geographical 
  area 
  of 
  PacJii/tylus 
  migraiorius 
  : 
  1. 
  ,i 
  

   The 
  limits 
  of 
  its 
  permanent 
  distribution. 
  2. 
  The 
  limit 
  of 
  its 
  temporary 
  existence 
  in 
  all 
  

   stages 
  of 
  development, 
  a 
  little 
  more 
  to 
  the 
  north. 
  Finally, 
  3. 
  The 
  limits 
  of 
  its 
  presence 
  

   in 
  the 
  condition 
  of 
  bands 
  of 
  winged 
  insects 
  of 
  a 
  stated 
  age, 
  out 
  of 
  the 
  regions 
  where 
  

   the 
  species 
  may 
  live 
  and 
  propagate. 
  It 
  will 
  be 
  necessary 
  still 
  to 
  establish 
  the 
  limits 
  of 
  

   accidental 
  individual 
  appearances, 
  but 
  that 
  would 
  be 
  of 
  questionable 
  importance. 
  The 
  

   northern 
  limit 
  of 
  tht^ 
  permanent 
  geographical 
  distribution 
  of 
  Pachytylus 
  migratorius 
  

   begins 
  in 
  Western 
  Europe, 
  from 
  the 
  coast 
  of 
  Portugal, 
  near 
  40° 
  latitude 
  north, 
  and 
  ex- 
  

   tends 
  from 
  there 
  toward 
  the 
  northeast 
  as 
  far 
  as 
  the 
  mouth 
  of 
  the 
  Bidassoa, 
  thus 
  leaving 
  

   out 
  all 
  the 
  northwest 
  portion 
  of 
  Spain; 
  it 
  continues 
  to 
  rise 
  obliquely 
  in 
  France 
  up 
  as 
  

   far 
  north 
  as 
  the 
  lake 
  of 
  Geneva, 
  and 
  extends 
  east, 
  following 
  more 
  or 
  less 
  the 
  iorty- 
  

   eighth 
  degree 
  of 
  latitude, 
  and 
  embracing 
  Valois, 
  all 
  of 
  the 
  north 
  of 
  Italy, 
  Carinthia, 
  

   and 
  Hungary, 
  it 
  passes 
  into 
  Southern 
  Russia, 
  where 
  it 
  attains 
  nearly 
  the 
  fiftieth 
  de- 
  

   gree, 
  passes 
  likewise 
  across 
  the 
  middle 
  of 
  Siberia, 
  whence 
  it 
  passes 
  over 
  the 
  north 
  of 
  

   China, 
  to 
  end 
  in 
  Japan, 
  at 
  a 
  latitude 
  a 
  little 
  inferior 
  to 
  that 
  of 
  its 
  point 
  of 
  departure 
  

   in 
  Portngal, 
  leaving 
  out 
  the 
  island 
  of 
  Niphon. 
  M. 
  Koppen 
  remarks 
  that 
  all 
  this 
  limit 
  

   does 
  not 
  deviate 
  much 
  from 
  the 
  isothermaof 
  16° 
  R. 
  [68° 
  Fahr.] 
  for 
  the 
  month 
  of 
  June, 
  

   To 
  farther 
  circumscribe 
  the 
  area, 
  so 
  extensive, 
  of 
  this 
  species, 
  the 
  line 
  goes 
  from 
  Japan 
  

   to 
  the 
  islands 
  of 
  Fidochi, 
  to 
  New 
  Zealand 
  and 
  Australia, 
  of 
  which 
  it 
  only 
  embraces 
  

   the 
  northern 
  parts, 
  passes 
  from 
  there 
  to 
  the 
  island 
  of 
  Mauritius, 
  then 
  rises 
  to 
  the 
  

   north, 
  crosses 
  Africa 
  up 
  to 
  Madeira. 
  But 
  in 
  this 
  last 
  part 
  of 
  the 
  passage 
  the 
  limits 
  are 
  

   more 
  hy|)otijetical, 
  from 
  want 
  of 
  an 
  exact 
  knowledge 
  of 
  the 
  existence 
  of 
  the 
  species 
  in 
  

   the 
  interior 
  of 
  Africa. 
  

  

  When, 
  in 
  a 
  country 
  comprised 
  in 
  this 
  area, 
  as 
  has 
  Tseen 
  frequently 
  observed 
  in 
  

   Southern 
  Russia, 
  the 
  locusts 
  develop 
  in 
  a 
  certain 
  abundance, 
  the 
  want 
  of 
  food 
  obliges 
  

   them 
  to 
  migrate 
  in 
  part 
  in 
  different 
  directions, 
  and 
  to 
  bteak 
  over 
  their 
  limits. 
  If 
  cir- 
  

   cumstances 
  permit 
  these 
  emigrants 
  to 
  multiply 
  for 
  a 
  certain 
  period 
  beyond 
  their 
  nor- 
  

   mal 
  area, 
  there 
  results 
  a 
  temporary 
  exten.sion 
  of 
  this 
  area, 
  and 
  occasionally 
  new 
  mi- 
  

   grations 
  to 
  the 
  north, 
  r;ntil 
  only 
  a 
  single 
  spring, 
  colder 
  or 
  more 
  humid, 
  comes 
  to 
  put 
  an 
  

   end 
  to 
  their 
  invasion 
  and 
  to 
  oblige 
  tbem 
  to- 
  go 
  back 
  to 
  their 
  natural 
  limits. 
  Tempo- 
  

   rary 
  extensions 
  like 
  this 
  of 
  the 
  area 
  of 
  distribution 
  of 
  Pachytylus 
  migratorius 
  took 
  

   place 
  in 
  1746 
  to 
  1749, 
  and 
  in 
  1822 
  to 
  1828 
  ; 
  at 
  these 
  periods 
  they 
  appeared 
  in 
  Germany, 
  

   and 
  have 
  multiplied 
  themselves 
  during 
  several 
  successive 
  years. 
  The 
  northern 
  limit 
  

   of 
  these 
  temporary 
  extensions 
  may 
  be 
  also 
  marked 
  on 
  the 
  chart 
  by 
  a 
  line 
  which, 
  tak- 
  

   ing 
  its 
  point 
  of 
  departure 
  in 
  the 
  southwestern 
  portion 
  of 
  Bavaria 
  (where 
  the 
  Pachyty- 
  

   lus 
  migratorius 
  has 
  been 
  observed 
  from 
  1333 
  to 
  1339, 
  and 
  from 
  1748 
  to 
  1749), 
  rises 
  to 
  

   the 
  northeast 
  by 
  Jena 
  and 
  Halle 
  toward 
  Jflterbogk 
  and 
  Berlin, 
  when 
  it 
  takes 
  a 
  nearly 
  

   eastern 
  course, 
  following 
  more 
  or 
  less 
  the 
  parallel 
  of 
  52^° 
  of 
  latitude, 
  near 
  Miincheberg, 
  

   Kiistrin, 
  Birnbaum, 
  and 
  Posen 
  (regions 
  which 
  the 
  species 
  was 
  known 
  to 
  have 
  visited 
  in 
  

   1730, 
  1752, 
  and 
  from 
  1827 
  to 
  1828) 
  ; 
  then 
  the 
  line 
  passes 
  across 
  Southern 
  Poland, 
  at 
  the 
  

   lifty-second 
  parallel, 
  through 
  the 
  southern 
  partofthe 
  government 
  of 
  the 
  Mohilew, 
  inclin- 
  

   ing 
  gradually 
  toward 
  the 
  south, 
  and 
  extending 
  so 
  as 
  to 
  reach 
  the 
  Wolga 
  and 
  the 
  Ural. 
  

   It 
  is 
  apparently 
  to 
  the 
  humidity 
  of 
  the 
  climate, 
  injurious 
  to 
  the 
  locust, 
  likewise 
  to 
  the 
  

   state 
  of 
  the 
  eggs 
  during 
  the 
  winter, 
  that 
  we 
  should 
  attribute 
  the 
  less 
  extension 
  ol 
  

   this 
  limit 
  toward 
  the 
  north 
  in 
  Western 
  Europe. 
  

  

  To 
  the 
  north 
  of 
  the 
  limits 
  which 
  have 
  just 
  been 
  indicated, 
  the 
  Pachytylus 
  migratorius 
  

   has 
  not 
  the 
  power 
  of 
  undergoing 
  its 
  whole 
  cycle 
  of 
  metamorphoses, 
  neither, 
  conse- 
  

   quently, 
  to 
  reproduce 
  itself. 
  This 
  does 
  not 
  prevent 
  its 
  occasional 
  appearance 
  in 
  swarms 
  

  

  