﻿110 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  That 
  heat 
  and 
  dryness 
  are 
  the 
  climatic 
  conditions 
  most 
  favorable 
  to 
  

   the 
  development 
  and 
  migrations 
  of 
  the 
  locusts 
  has 
  been 
  maintained 
  by- 
  

   all 
  who 
  have 
  paid 
  any 
  particular 
  attention 
  to 
  the 
  subject 
  and 
  have 
  ex- 
  

   pressed 
  their 
  views 
  in 
  reference 
  thereto. 
  Koppen 
  204 
  asserts 
  that 
  "Heat 
  

   and 
  dryness 
  are 
  both 
  necessary 
  to 
  the 
  extraordinary 
  increase 
  of 
  the 
  

   locusts;" 
  and 
  the 
  views 
  of 
  other 
  European 
  entomologists 
  accord 
  with 
  

   this. 
  In 
  our 
  former 
  report 
  we 
  expressed 
  the 
  same 
  opinion 
  in 
  reference 
  

   to 
  the 
  development 
  and 
  migrations 
  of 
  the 
  Eocky 
  Mountain 
  locusts. 
  

   Some 
  attempt 
  to 
  show 
  this 
  by 
  the 
  meteorological 
  records 
  was 
  made, 
  and 
  

   although 
  not 
  so 
  full 
  and 
  satisfactory 
  as 
  we 
  desired, 
  was 
  all 
  we 
  were 
  then 
  

   able 
  to 
  present, 
  as 
  there 
  was 
  not 
  time, 
  previous 
  to 
  the 
  date 
  fixed 
  for 
  

   publication, 
  to 
  examine 
  and 
  discuss 
  thoroughly 
  these 
  records 
  in 
  their 
  

   bearing 
  upon 
  this 
  subject, 
  though 
  the 
  material 
  was 
  readily 
  furnished 
  by 
  

   the 
  courtesy 
  of 
  the 
  Chief 
  Signal- 
  Officer, 
  to 
  whom 
  we 
  are 
  under 
  many 
  

   obligations 
  for 
  favors 
  on- 
  this 
  subject. 
  A 
  further 
  examination 
  of 
  the 
  

   older 
  records 
  and 
  of 
  new 
  data 
  which 
  have 
  been 
  very 
  kindly 
  prepared 
  

   and 
  furnished 
  us 
  by 
  the 
  Signal 
  Service 
  Bureau, 
  a 
  summary 
  of 
  which 
  is 
  

   here 
  presented, 
  has 
  served 
  to 
  somewhat 
  modify 
  our 
  views 
  on 
  this 
  point. 
  

   Not 
  that 
  it 
  has 
  caused 
  us 
  to 
  doubt 
  the 
  general 
  correctness 
  of 
  the 
  state- 
  

   ment 
  that 
  heat 
  and 
  dryness 
  are 
  the 
  climatic 
  conditions 
  most 
  favorable 
  

   to 
  the 
  increase 
  of 
  locusts, 
  and 
  hence 
  of 
  their 
  distribution 
  by 
  migration, 
  

   but 
  that 
  the 
  mode 
  in 
  which 
  these 
  influences 
  operate 
  is 
  not 
  precisely, 
  nor 
  

   so 
  direct 
  and 
  immediate, 
  as 
  heretofore 
  supposed. 
  But 
  before 
  discussing 
  

   the 
  point 
  we 
  will 
  present 
  our 
  additional 
  meteorological 
  data, 
  referring 
  

   the 
  reader 
  to 
  what 
  has 
  been 
  given 
  in 
  our 
  former 
  report 
  in 
  order 
  to 
  avoid 
  

   repeating 
  it 
  here. 
  

  

  As 
  we 
  shall 
  have 
  occasion 
  to 
  refer 
  repeatedly 
  to 
  Mr. 
  Packard's 
  table 
  

   of 
  locust 
  years, 
  we 
  insert 
  it 
  here 
  as 
  a 
  means 
  of 
  ready 
  reference. 
  

  

  ^Heuschr. 
  SM-Russ, 
  68. 
  

  

  