﻿[22] 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  Some 
  important 
  inferences 
  can 
  be 
  drawn 
  from 
  these 
  facts. 
  The 
  mag- 
  

   gots 
  occurring 
  in 
  the 
  stubble 
  in 
  spring 
  cannot 
  possibly 
  belong 
  to 
  the 
  

   winter 
  generation, 
  that 
  is, 
  Irom 
  eggs 
  laid 
  in 
  fall; 
  such 
  an 
  acceptation 
  

   would 
  not 
  accord 
  with 
  the 
  manner 
  of 
  nourishment 
  of 
  the 
  maggot. 
  We 
  

   therefore 
  infer 
  that 
  some 
  individuals 
  of 
  the 
  summer 
  generation, 
  perhaps 
  

   owing 
  to 
  very 
  cold 
  nights 
  which 
  occurred 
  a 
  little 
  after 
  October 
  1, 
  hiber- 
  

   nated 
  and 
  then 
  dev^eloped 
  into 
  tlie 
  imago. 
  The 
  manner 
  of 
  the 
  occurrence 
  

   of 
  the 
  imago 
  verified 
  thisfif' 
  The 
  scythe 
  was, 
  on 
  account 
  of 
  the 
  clover, 
  

   kept 
  high, 
  usually 
  cutting 
  off 
  above 
  the 
  dwellings 
  of 
  the 
  maggots, 
  and 
  

   the 
  upper 
  part 
  of 
  the 
  bent 
  stubble 
  or 
  the 
  blade 
  remaining 
  after 
  the 
  de- 
  

   cay 
  of 
  the 
  stubble 
  became 
  a 
  protecting 
  cover 
  for 
  the 
  hibernating 
  insect. 
  

   Occasionally 
  one 
  or 
  several 
  maggots 
  occurred 
  amongst 
  empty 
  pupa 
  cases, 
  

   whose 
  former 
  occupants, 
  therefore, 
  had 
  been 
  in 
  sisterly 
  relation 
  to 
  them. 
  

   These 
  and 
  several 
  other 
  observations 
  remind 
  one 
  so 
  closely 
  of 
  even 
  the 
  

   most 
  detailed 
  circumstances 
  of 
  the 
  occurrence 
  of 
  the 
  maggots 
  during 
  

   the 
  previous 
  summer, 
  as 
  not 
  at 
  all 
  to 
  suggest 
  a 
  w^inter 
  generation. 
  

  

  Since 
  at 
  the 
  time 
  when 
  the 
  disturbing 
  external 
  cause 
  appeared, 
  many 
  

   of 
  the 
  insects 
  certainly 
  lived 
  not 
  in 
  the 
  larval 
  but 
  in 
  the 
  pupal 
  state, 
  

   and 
  yet 
  no 
  pupai 
  were 
  found 
  in 
  March 
  ; 
  it 
  follows 
  that 
  only 
  the 
  maggots 
  

   hibernated. 
  

  

  We 
  still 
  lack 
  any 
  special 
  knowledge 
  as 
  to 
  the 
  temperature 
  required 
  

   for 
  each 
  of 
  the 
  four 
  life-periods 
  w^hen 
  no 
  cessation 
  of 
  development 
  

   should 
  occur. 
  This 
  temi)erature 
  is 
  evidently 
  in 
  many 
  cases 
  so 
  unequal 
  

   that 
  each 
  successive 
  state 
  requires 
  a 
  gradually 
  increased 
  temperature. 
  

   The 
  looked-for 
  opportunity 
  is 
  seldom 
  oflered 
  that 
  a 
  larva 
  in 
  its 
  earlier 
  

   stages 
  continues 
  to 
  develoj) 
  at 
  a 
  certain 
  temperature, 
  while 
  another 
  

   more 
  advanced 
  one 
  is 
  arrested 
  in 
  its 
  growth 
  only 
  to 
  resume 
  growth 
  again 
  

   at 
  more 
  favorable 
  weather. 
  Of 
  this 
  we 
  have 
  in 
  our 
  fly 
  a 
  conspicuous 
  ex- 
  

   ainjile. 
  The 
  maggots 
  examined 
  at 
  the 
  end 
  of 
  March 
  from 
  the 
  stubbles 
  

   allowed 
  us 
  to 
  see 
  nothing 
  from 
  which 
  to 
  infer 
  that 
  they 
  approached 
  the 
  

   pnpa 
  state 
  more 
  than 
  those 
  examined 
  the 
  previous 
  September; 
  the 
  latter, 
  

   therefore, 
  were 
  already 
  full-grown, 
  having 
  ceased 
  to 
  grow 
  for 
  the 
  length 
  

   of 
  half 
  a 
  year. 
  Kot 
  so 
  the 
  maggots 
  of 
  the 
  winter 
  generation 
  ; 
  after 
  they 
  

   ha<l 
  previously 
  underj;one 
  the 
  first 
  phases 
  of 
  their 
  larval 
  state, 
  they 
  de- 
  

   veloped 
  during 
  the 
  warm 
  days 
  between 
  December 
  4 
  and 
  16 
  so 
  rapidly 
  

   that 
  they 
  overtook 
  those 
  on 
  stubble, 
  and 
  then 
  began 
  their 
  hibernation, 
  

   enduring 
  in 
  it 
  till 
  March. 
  From 
  this 
  it 
  follows 
  that 
  the 
  time 
  of 
  swarm- 
  

   ing 
  of 
  those 
  hibernating 
  on 
  stubbles 
  for 
  the 
  greater 
  part 
  corresponds 
  

   with 
  the 
  actual 
  winter 
  generation. 
  But 
  if 
  that 
  extremely 
  favorable 
  De- 
  

   cember 
  w^eather 
  had 
  not 
  set 
  in 
  the 
  same 
  could 
  have 
  happened, 
  since, 
  as 
  

   just 
  demonstrated, 
  the 
  two 
  kinds 
  of 
  maggots 
  do 
  not 
  always 
  conduct 
  them- 
  

   selves 
  alike 
  tow^ard 
  the 
  temperature 
  of 
  the 
  air; 
  the 
  maggots 
  of 
  the 
  winter 
  

   generation 
  would 
  in 
  this 
  case 
  have 
  made 
  up 
  In 
  spring 
  what 
  the 
  winter 
  

   made 
  them 
  unable 
  to 
  accomplish 
  before 
  the 
  maggots 
  on 
  the 
  stubble 
  had 
  

   awakened 
  from 
  their 
  long 
  shnnber. 
  As 
  we 
  hold 
  to 
  the 
  j)resent 
  facts, 
  we 
  

   see 
  in 
  the 
  hibernation 
  on 
  stubble 
  the 
  cause 
  of 
  a 
  partial 
  prolongation 
  

   of 
  the 
  swarming 
  time, 
  which 
  will 
  certainly 
  be 
  transferred 
  also 
  to 
  the 
  

   snmmer 
  generation. 
  Therefore 
  we 
  can, 
  as 
  is 
  assumed, 
  if 
  we 
  adjudge 
  

   the 
  rye-hibernating 
  insects 
  a 
  somewhat 
  later 
  swarming 
  time, 
  consider 
  

   the 
  second 
  half 
  of 
  April 
  and 
  the 
  first 
  two-thirds 
  of 
  May 
  as 
  the 
  duration 
  

   of 
  the 
  spring 
  swarming. 
  

  

  The 
  hibernation 
  of 
  the 
  insect 
  on 
  stubble 
  gives 
  us 
  a 
  key 
  to 
  a 
  judgment 
  

   of 
  the 
  very 
  probable 
  behavior 
  in 
  variously 
  ditfering 
  latitudes. 
  Since 
  

   the 
  theory 
  may 
  be 
  considered 
  valid, 
  that 
  the 
  required 
  time 
  for 
  the 
  de- 
  

   veIo]>ment 
  of 
  an 
  insect 
  remains 
  the 
  same 
  only 
  under 
  the 
  same 
  external 
  

   conditions, 
  but 
  a 
  change 
  of 
  the 
  latter 
  must 
  necessarily 
  be 
  accompanied 
  

  

  