﻿98 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

   6. 
  THE 
  HEIGHT 
  AT 
  WHICH 
  SWARMS 
  MOVE. 
  

  

  Iii 
  studying 
  the 
  flights 
  of 
  G. 
  spretus 
  over 
  the 
  temporary 
  region 
  certain 
  

   facts, 
  as 
  the 
  sudden 
  appearance 
  of 
  swarms 
  in 
  the 
  afternoon 
  of 
  bright, 
  

   clear 
  days 
  at 
  certain 
  points, 
  when 
  nothing 
  had 
  been 
  seen 
  or 
  heard 
  of 
  

   them 
  over 
  the 
  surrounding 
  area; 
  and 
  large 
  swarms 
  departing 
  from 
  one 
  

   section 
  in 
  a 
  certain 
  direction 
  over 
  a 
  well-settled 
  area, 
  though 
  nothing 
  

   could 
  be 
  seen 
  or 
  heard 
  of 
  them 
  in 
  that 
  direction, 
  &c, 
  led 
  us 
  to 
  investigate 
  

   this 
  subject 
  also 
  with 
  special 
  care, 
  to 
  ascertain, 
  if 
  possible, 
  how 
  this 
  was 
  

   to 
  be 
  accounted 
  for. 
  

  

  There 
  appeared 
  to 
  be 
  no 
  other 
  possible 
  solution 
  of 
  the 
  problem 
  than 
  

   that 
  the 
  swarms 
  flew 
  at 
  such 
  a 
  height 
  as 
  to 
  be 
  entirely 
  out 
  of 
  sight. 
  

  

  Observations 
  of 
  flying 
  swarms 
  soon 
  made 
  it 
  apparent 
  that 
  although, 
  

   when 
  seen 
  at 
  some 
  distance 
  approaching 
  and 
  flying 
  rather 
  low, 
  the 
  

   swarm 
  is 
  observed 
  as 
  a 
  mass 
  resembling 
  a 
  cloud, 
  yet 
  when 
  passing 
  over- 
  

   head 
  the 
  locusts 
  are 
  seen 
  only 
  as 
  individuals. 
  This 
  fact 
  rendered 
  it 
  ev- 
  

   ident 
  that 
  the 
  height 
  at 
  which 
  it 
  was 
  possible 
  to 
  see 
  them 
  was 
  much 
  

   less 
  than 
  would 
  generally 
  be 
  supposed 
  from 
  the 
  descriptions 
  of 
  locust 
  

   flights 
  given 
  by 
  travelers 
  in 
  the 
  Old 
  World. 
  It 
  is 
  also 
  probable 
  that 
  what 
  

   is 
  said 
  here 
  in 
  reference 
  to 
  the 
  invisibility 
  of 
  swarms 
  of 
  Eocky 
  Mount- 
  

   ain 
  locusts 
  is 
  not 
  fully 
  applicable 
  to 
  swarms 
  of 
  the 
  larger 
  Oriental 
  spe- 
  

   cies. 
  

  

  It 
  is 
  not 
  possible 
  to 
  determine 
  with 
  any 
  exactitude 
  the 
  height 
  of 
  

   swarms 
  even 
  when 
  visible, 
  as 
  they 
  do 
  not 
  move 
  in 
  broad 
  sheets, 
  as 
  many 
  

   who 
  have 
  never 
  observed 
  a 
  flight 
  imagine, 
  nor 
  are 
  they 
  generally 
  in 
  a 
  

   compact 
  body 
  whose 
  boundary 
  is 
  well 
  defined, 
  forming 
  a 
  clear 
  line, 
  but 
  

   more 
  like 
  a 
  vast 
  body 
  of 
  fleecy 
  clouds, 
  or, 
  still 
  more 
  correctly, 
  a 
  cloud 
  of 
  

   snow 
  flakes, 
  often 
  having 
  a 
  depth 
  that 
  reaches 
  from 
  comparatively 
  near 
  

   the 
  ground 
  to 
  a 
  height 
  that 
  baffles 
  the 
  keenest 
  eye 
  to 
  distinguish 
  the 
  

   insects 
  in 
  the 
  upper 
  stratum. 
  Professor 
  Aughey 
  has 
  made 
  some 
  at- 
  

   tempts 
  at 
  measuring 
  the 
  height 
  of 
  swarms, 
  and 
  in 
  some 
  instances 
  has 
  

   succeeded 
  in 
  ascertaining 
  pretty 
  correctly 
  the 
  elevation 
  above 
  the 
  sur- 
  

   face, 
  and 
  also 
  the 
  depth 
  of 
  the 
  swarm. 
  But 
  the 
  only 
  important 
  question 
  

   to 
  be 
  decided 
  in 
  reference 
  to 
  this 
  point 
  is, 
  whether 
  they 
  can 
  and 
  do 
  fly 
  

   at 
  an 
  elevation 
  so 
  great 
  as 
  to 
  carry 
  the 
  entire 
  swarm 
  out 
  of 
  view 
  on 
  a 
  

   clear 
  day. 
  

  

  The 
  facts 
  already 
  mentioned, 
  which 
  could 
  be 
  accounted 
  for 
  in 
  no 
  other 
  

   way, 
  and 
  which 
  were 
  of 
  repeated 
  occurrence, 
  render 
  this 
  not 
  only 
  highly 
  

   probable, 
  but 
  almost 
  certain, 
  and 
  we 
  would 
  be 
  justified 
  in 
  assuming 
  the 
  

   affirmative 
  even 
  if 
  we 
  had 
  no 
  other 
  evidence. 
  

  

  But, 
  as 
  stated 
  in 
  our 
  former 
  report, 
  the 
  strongest 
  evidence 
  in 
  favor 
  of 
  

   the 
  view 
  that 
  they 
  do 
  often 
  fly 
  at 
  an 
  elevation 
  above 
  the 
  plains 
  of 
  the 
  

   border 
  States 
  which 
  renders 
  them 
  entirely 
  bej^ond 
  the 
  natural 
  vision, 
  is 
  

   the 
  fact 
  that 
  they 
  can 
  fly 
  at 
  that 
  height. 
  That 
  it 
  is 
  no 
  uncommon 
  thing 
  

   for 
  cranes 
  and 
  wild 
  geese 
  to 
  fly 
  north 
  and 
  south 
  along 
  the 
  Mississippi 
  

  

  