﻿74 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  tioiis 
  of 
  the 
  locust 
  have 
  been, 
  broadly 
  speaking, 
  in 
  a 
  southerly 
  direc- 
  

   tion 
  east 
  and 
  west 
  of 
  this 
  region, 
  and 
  if 
  reference 
  be 
  made 
  to 
  Mr. 
  Pack- 
  

   ard's 
  analytical 
  table 
  given 
  in 
  the 
  report 
  of 
  the 
  Commission 
  for 
  the 
  year 
  

   1877 
  (p. 
  113), 
  and 
  the 
  year 
  1878-'79 
  (p. 
  Ill), 
  we 
  shall 
  find 
  that 
  these 
  

   have 
  waxed 
  and 
  waned, 
  that 
  one 
  climax 
  transpired 
  between 
  1874 
  and 
  

   1876, 
  that 
  another 
  transpired 
  between 
  1866 
  and 
  1867, 
  that 
  another 
  trans- 
  

   pired 
  between 
  1855 
  and 
  1857, 
  and 
  there 
  remains 
  besides 
  some 
  indica- 
  

   tions 
  of 
  an 
  invasion 
  about 
  1842. 
  Kow 
  by 
  Wolfs 
  tables 
  of 
  sun-spots 
  

   1876, 
  1867, 
  1855, 
  and 
  1843, 
  severally 
  ta^ngential 
  nuufbers, 
  are 
  the 
  years 
  

   of 
  fewest 
  sun-spots 
  as 
  determined 
  by 
  observation. 
  In 
  this 
  case 
  there- 
  

   fore 
  the 
  season 
  of 
  multiplication 
  and 
  migration 
  has 
  preponderated 
  to 
  

   the 
  minimum 
  period 
  of 
  solar 
  spots 
  j 
  and 
  conversely 
  about 
  1848, 
  1860, 
  

   1870, 
  and 
  as 
  I 
  conclude 
  also 
  in 
  1881, 
  the 
  intermediate 
  years 
  of 
  most 
  

   sun-spots, 
  the 
  decrease 
  and 
  restriction 
  of 
  this 
  locust 
  are 
  equally 
  ap- 
  

   parent. 
  

  

  But 
  to 
  fully 
  illustrate 
  this 
  subject, 
  I 
  will 
  turn 
  to 
  the 
  insect 
  multipli- 
  

   cation 
  and 
  migration 
  of 
  the 
  Old 
  World, 
  where 
  the 
  data 
  are 
  more 
  copious 
  

   and 
  the 
  subject 
  matter 
  more 
  familiar. 
  Here 
  we 
  know 
  as 
  regards 
  the 
  

   multiplication 
  and 
  migration 
  of 
  various 
  locusts 
  in 
  the 
  cereal 
  districts 
  on 
  

   the 
  southern 
  borders 
  of 
  Europe 
  and 
  Northern 
  Asia, 
  from 
  long 
  tradition 
  

   since 
  the 
  earliest 
  days, 
  that 
  those 
  droughts 
  which 
  have 
  been 
  previously 
  

   attributed 
  to 
  the 
  minimum 
  epochs 
  of 
  the 
  sun-spot 
  cycle 
  are 
  their 
  season 
  

   of 
  increase. 
  But, 
  as 
  I 
  have 
  already 
  intimated 
  (Journal 
  of 
  Science 
  for 
  

   August, 
  1881), 
  it 
  cannot 
  be 
  therefore 
  assumed 
  that 
  all 
  destructive 
  insects 
  

   on 
  European 
  areas 
  have 
  the 
  same 
  period 
  of 
  multiplication; 
  for 
  while 
  

   the 
  corn 
  weevils 
  {Sitophilus 
  granarius 
  and 
  oryzce) 
  of 
  our 
  granaries, 
  or 
  

   certainly 
  the 
  more 
  destructive 
  sort 
  which 
  is 
  imported 
  from 
  the 
  marts 
  

   of 
  the 
  south, 
  have 
  shown 
  a 
  tendency 
  to 
  increase 
  about 
  the 
  minimum 
  of 
  

   spots, 
  it 
  would 
  appear 
  that 
  the 
  noxious 
  European 
  wheat 
  flies 
  {Diplosis)^ 
  

   of 
  which 
  there 
  are 
  said 
  to 
  be 
  two 
  varieties, 
  affect 
  in 
  German}^ 
  a 
  decen- 
  

   nial 
  period 
  recurring 
  towards 
  the 
  maximum 
  years. 
  This 
  phenomenon 
  

   may 
  be 
  either 
  attributable 
  to 
  the 
  circumstance 
  that 
  insects 
  are 
  vari- 
  

   ously 
  adapted 
  to 
  various 
  conditions 
  of 
  climate, 
  and 
  that 
  there 
  are 
  cer- 
  

   tain 
  recurring 
  times 
  when 
  certain 
  families 
  and 
  certain 
  individuals 
  find 
  

   themselves 
  in 
  the 
  most 
  congenial 
  conditions 
  for 
  multiplication 
  j 
  or 
  to 
  

   the 
  circumstance 
  that 
  there 
  exist 
  fixed 
  epochs 
  when 
  a 
  general 
  north 
  

   and 
  west 
  move 
  is 
  witnessed 
  iu 
  the 
  mass 
  of 
  the 
  European 
  insect 
  fauna. 
  

   These 
  latter 
  times 
  or 
  epochs, 
  north 
  of 
  about 
  45^ 
  north 
  latitude, 
  alter- 
  

   nate, 
  as 
  I 
  shall 
  proceed 
  to 
  show, 
  with 
  the 
  extremes 
  of 
  solar 
  energy, 
  so 
  

   that 
  the 
  great 
  European 
  migrations 
  of 
  insects 
  take 
  their 
  rise 
  in 
  the 
  

   years 
  of 
  minimum 
  sun-spots, 
  and 
  continue 
  until 
  the 
  expiration 
  of 
  the 
  

   succeeding 
  maximum. 
  Let 
  us 
  exemplify 
  this 
  first, 
  in 
  passing, 
  by 
  Kop- 
  

   pen's 
  record 
  of 
  the 
  migration 
  of 
  locusts 
  to 
  Southern 
  Eussia, 
  given 
  by 
  

   Mr. 
  Thomas.^^ 
  Here 
  there 
  is 
  a 
  migration 
  extending 
  from 
  1756 
  to 
  1757 
  

   indicated, 
  then 
  a 
  break 
  until 
  1783, 
  then 
  another 
  break 
  until 
  1793, 
  and 
  

  

  i^Keport 
  of 
  the 
  Eutomological 
  Comniissiou 
  on 
  the 
  Kocky 
  Monntain 
  Locust, 
  for 
  1878-79, 
  p. 
  41. 
  

  

  