﻿FLUCTUATIONS 
  IN 
  MONTHLY 
  MEAN 
  TEMPERATURE. 
  

  

  125 
  

  

  • 
  I 
  in 
  the 
  egg 
  and 
  larval 
  states 
  to 
  a 
  given 
  degree 
  of 
  heat 
  — 
  this 
  can 
  only 
  

   be 
  obtained 
  accurately 
  by 
  the 
  daily 
  records, 
  but 
  should 
  be 
  indicated 
  by 
  

   a 
  comparison 
  of 
  the 
  monthjy 
  means. 
  This 
  point 
  is 
  not 
  considered 
  in 
  

  

  the 
  discussion 
  of 
  these 
  tables, 
  but 
  will 
  he 
  alluded 
  to 
  further 
  on. 
  

  

  Two 
  conditions 
  are 
  absolutely 
  necessary 
  to 
  excessive 
  development 
  ; 
  

   first, 
  that 
  the 
  parents 
  shall 
  be 
  in 
  a 
  healthy 
  condition 
  and 
  properly 
  de- 
  

   posit 
  the 
  eggs; 
  rid, 
  that 
  the 
  eggs 
  shall 
  very 
  generally 
  hatch 
  out. 
  

  

  There 
  are 
  other 
  conditions 
  that 
  retard 
  or 
  favor, 
  but 
  these 
  are 
  absolutely 
  

   necessary. 
  It 
  follows, 
  therefore, 
  that 
  there 
  are 
  critical 
  periods 
  in 
  the 
  

   life 
  of 
  the 
  insect, 
  and 
  hence 
  it 
  may 
  be 
  necessary, 
  in 
  order 
  to 
  ascertain 
  

   the 
  meteorological 
  conditions 
  favoring 
  the 
  development 
  of 
  excessive 
  

   numbers 
  in 
  one 
  year, 
  to 
  examine 
  the 
  meteorological 
  records 
  of 
  the 
  pre- 
  

   vious 
  years. 
  

  

  Another 
  fact 
  to 
  be 
  taken 
  into 
  consideration 
  in 
  the 
  discussion 
  is 
  that, 
  

   although 
  excessive 
  numbers 
  may 
  hatch, 
  they 
  may 
  be 
  killed, 
  greatly 
  

   diminished, 
  or 
  rendered 
  diseased 
  by 
  unusual 
  moisture 
  ; 
  or 
  their 
  devel- 
  

   opment 
  may 
  be 
  retarded, 
  and 
  migrating 
  to 
  a 
  great 
  degree 
  prevented, 
  by 
  

   unusually 
  low 
  temperature. 
  

  

  Bearing 
  these 
  facts 
  in 
  mind 
  and 
  remembering 
  also 
  that 
  1874 
  and 
  1876 
  

   were 
  the 
  years 
  of 
  the 
  great 
  locust 
  invasions, 
  let 
  us 
  see 
  if 
  any 
  important 
  

   fact 
  bearing 
  upon 
  the 
  subject- 
  can 
  be 
  drawn 
  from 
  the 
  foregoing 
  table 
  of 
  

   the 
  monthly 
  temperature 
  of 
  the 
  Northwest 
  in 
  the 
  locust 
  area. 
  

  

  If 
  we 
  examine 
  the 
  fluctuations 
  in 
  the 
  same 
  month 
  for 
  the 
  different 
  

   years 
  and 
  select 
  the 
  extreme 
  variations 
  — 
  that 
  is, 
  the 
  difference 
  between 
  

   the 
  highest 
  and 
  lowest 
  means 
  — 
  we 
  shall 
  find 
  them 
  to 
  be 
  as 
  shown 
  in 
  

   Table 
  VIII. 
  

  

  Table 
  VIII. 
  Extreme 
  fluctuations 
  in 
  mon 
  

  

  thiy 
  

  

  mean 
  temperature. 
  

  

  

  

  

  

  3c 
  

  

  

  

  1 
  

  

  

  

  

  = 
  

  

  

  i- 
  

  

  

  

  

  3 
  >. 
  

  

  

  

  — 
  

  

  z 
  

  

  

  _. 
  

  

  

  2 
  

  

  

  o 
  

  

  . 
  

  

  

  Months. 
  

  

  oil, 
  Sull 
  

   illiUtnn. 
  

  

  i 
  

  

  = 
  

  

  M 
  

   z 
  

   5 
  

  

  - 
  

  

  — 
  

   = 
  

   '- 
  

  

  = 
  

  

  - 
  

   - 
  

  

  1 
  

  

  — 
  

   | 
  

  

  =■ 
  

   a 
  

  

  > 
  

   a 
  

  

  • 
  

  

  z 
  

  

  — 
  

  

  ■a 
  

  

  Z 
  

  

  1 
  

  

  u. 
  

  

  i 
  

  

  i 
  

  

  J 
  

  

  © 
  

  

  = 
  

   Z 
  

   > 
  

  

  

  - 
  * 
  > 
  

  

  5 
  

  

  M 
  

  

  QG 
  

  

  h3 
  

  

  v. 
  

  

  o 
  

  

  - 
  

  

  '- 
  

  

  5 
  

  

  > 
  n 
  

  

  < 
  

  

  

  z 
  a 
  

  

  

  

  z 
  

  

  T 
  

  

  o 
  

  

  o 
  

  

  

  

  o 
  

  

  

  

  c 
  

  

  . 
  . 
  

  

  

  January 
  

  

  24. 
  2 
  IS. 
  6 
  21. 
  2 
  

  

  12.8 
  

  

  17. 
  4 
  24. 
  9 
  18. 
  7 
  

  

  10. 
  3 
  17. 
  9 
  14. 
  7 
  

  

  25. 
  1 
  16. 
  4 
  

  

  21. 
  7 
  26. 
  4 
  

  

  19.3 
  

  

  February 
  

  

  35. 
  3 
  19. 
  2 
  33. 
  9 
  

  

  16.3 
  

  

  .20. 
  3 
  33. 
  8 
  17. 
  9 
  

  

  6.2 
  8.013.0 
  

  

  8. 
  5 
  30. 
  12. 
  5 
  33. 
  7 
  

  

  20.6 
  

  

  Mar 
  c 
  h 
  . 
  . 
  

  

  38. 
  8 
  16. 
  5 
  13. 
  

  

  18.8 
  

  

  17. 
  7 
  22. 
  4 
  15. 
  -j 
  

  

  10. 
  15. 
  4 
  la 
  9 
  

  

  23. 
  1 
  29. 
  7 
  15. 
  27. 
  3 
  19. 
  & 
  

  

  April 
  

  

  13.6 
  5.510.4 
  

  

  10.8 
  

  

  12. 
  9 
  13. 
  6 
  10. 
  2 
  

  

  8.1 
  9. 
  110.C 
  

  

  6. 
  7 
  16. 
  1 
  3. 
  3 
  13. 
  7 
  10. 
  3 
  

  

  May 
  

  

  9.0 
  8.7 
  7.9 
  8.1 
  

  

  6.9 
  7.1 
  

  

  5.0 
  

  

  5.4 
  8.7 
  

  

  8.6 
  

  

  6. 
  c 
  8. 
  9 
  7. 
  1 
  6. 
  1 
  7. 
  5 
  

  

  •June 
  

  

  10.610.6 
  7.6 
  

  

  5.8 
  

  

  7.8 
  9.4 
  

  

  6.9 
  

  

  6. 
  4 
  18. 
  

  

  6.1 
  

  

  2. 
  1 
  10. 
  4 
  

  

  5.8 
  2.4 
  

  

  

  July 
  

  

  10.4 
  5.7 
  6.4 
  

  

  5.6 
  

  

  4.2 
  3.7 
  6.5 
  

  

  5.9 
  8.3 
  

  

  8.3 
  

  

  5. 
  3 
  5. 
  

  

  3.9 
  1.6 
  

  

  

  August 
  

  

  4.0 
  4.7 
  8.8 
  

  

  7.1 
  

  

  7.1 
  5.6 
  8.2 
  

  

  4.7 
  6.0 
  

  

  4.0 
  

  

  0.4 
  3.3 
  

  

  6.7 
  3.5 
  

  

  5.3 
  

  

  September 
  

  

  9.4 
  7.9 
  6.6 
  

  

  6.6 
  

  

  6.2 
  12.5 
  2.5 
  

  

  2.7 
  3.1 
  

  

  2.9 
  

  

  7.4 
  9.4 
  

  

  5.7 
  6.8 
  

  

  6 
  4 
  

  

  October 
  

  

  6.910.2 
  4.0 
  

   6. 
  7 
  10. 
  7 
  10. 
  

  

  5.5 
  

   7.9 
  

  

  5.9 
  8.1 
  3.3 
  

   5. 
  6 
  8. 
  6 
  6. 
  8 
  

  

  6.2 
  7.9 
  

   8. 
  1 
  11. 
  9 
  

  

  9.4 
  

  

  in 
  8 
  fi 
  ft 
  

  

  ft 
  fi 
  <> 
  ft 
  

  

  6 
  8 
  

  

  November 
  

  

  9. 
  7 
  18. 
  14. 
  6 
  12. 
  11. 
  4 
  10. 
  1 
  

  

  December 
  

  

  28. 
  2 
  15. 
  5 
  22. 
  

  

  20.2 
  

  

  " 
  aa 
  9 
  n 
  8 
  in 
  ft 
  

  

  15. 
  4 
  93 
  i 
  

  

  

  

  

  

  

  

  

  " 
  

  

  

  ' 
  

  

  

  

  Average 
  variation 
  of 
  winter 
  and 
  spring 
  taken 
  together, 
  16.8 
  (that 
  is. 
  from 
  November 
  to 
  April). 
  

   Average 
  variation 
  of 
  summer 
  and 
  autumn 
  taken 
  together, 
  6.6 
  (that 
  is, 
  from 
  May 
  to 
  October). 
  

  

  In 
  this 
  table 
  each 
  number 
  in 
  a 
  column 
  shows 
  the 
  extreme 
  variation, 
  

   during 
  the 
  series 
  of 
  years 
  included 
  in 
  Table 
  VI, 
  of 
  the 
  mean 
  for 
  the 
  

   month 
  opposite, 
  and 
  at 
  the 
  station 
  mentioned 
  at 
  the 
  head 
  of 
  the 
  column. 
  

   For 
  example, 
  in 
  the 
  Breckenridge 
  column 
  24-.2 
  is 
  the 
  number 
  given 
  $ 
  

  

  