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  OBSERVATIONS 
  ON 
  THE 
  OVIPOSITION 
  OF 
  THE 
  HOUSE-FLY 
  IN 
  PANAMA. 
  303 
  

  

  within 
  a 
  few 
  minutes 
  after 
  dropping, 
  and 
  very 
  often 
  being 
  still 
  warm 
  when 
  brought 
  

   to 
  the 
  laboratory. 
  It 
  was 
  always 
  collected 
  in 
  a 
  tin 
  can 
  with 
  a 
  closely 
  fitting 
  

   cover. 
  After 
  reaching 
  the 
  laboratory 
  the 
  cover 
  of 
  the 
  can 
  was 
  partly 
  removed 
  

   and 
  it 
  was 
  sterilized 
  in 
  an 
  autoclave 
  with 
  steam 
  at 
  15 
  lb. 
  pressure 
  for 
  twenty 
  minutes. 
  

   When 
  removed 
  from 
  the 
  autoclave 
  at 
  the 
  end 
  of 
  this 
  time 
  the 
  cover 
  was 
  again 
  tightly 
  

   replaced 
  and 
  the 
  manure 
  was 
  left 
  until 
  the 
  following 
  morning 
  before 
  being 
  used. 
  

  

  When 
  ready 
  for 
  use 
  each 
  piece 
  was 
  carefully 
  inspected 
  for 
  eggs 
  before 
  being 
  

   placed 
  in 
  the 
  globe 
  with 
  the 
  flies. 
  If 
  any 
  were 
  found 
  — 
  which 
  happened 
  but 
  three 
  

   times 
  during 
  the 
  observations 
  — 
  the 
  manure 
  was 
  discarded 
  and 
  a 
  second 
  lot 
  used, 
  

   although 
  the 
  eggs 
  found 
  were 
  cooked 
  by 
  the 
  steaming. 
  As 
  a 
  further 
  preventive 
  

   against 
  counting 
  eggs 
  that 
  might 
  have 
  been 
  overlooked 
  in 
  the 
  search, 
  all 
  eggs 
  after 
  

   being 
  counted 
  were 
  allowed 
  to 
  hatch 
  as 
  an 
  extra 
  precaution. 
  Eggs 
  that 
  had 
  been 
  

   through 
  the 
  autoclave 
  were 
  of 
  course 
  rendered 
  non-viable 
  and 
  would 
  not 
  hatch. 
  

  

  When 
  supplying 
  material 
  to 
  a 
  pair 
  of 
  flies 
  a 
  piece 
  of 
  manure 
  about 
  the 
  size 
  of 
  a 
  

   walnut, 
  after 
  being 
  slightly 
  broken 
  open 
  to 
  provide 
  crevices 
  in 
  which 
  the 
  eggs 
  might 
  

   be 
  deposited, 
  was 
  placed 
  in 
  a 
  small 
  stender 
  dish, 
  H 
  in. 
  in 
  diameter 
  and 
  1 
  in. 
  in 
  height. 
  

   After 
  depositing 
  a 
  few 
  drops 
  of 
  milk 
  in 
  the 
  centre 
  of 
  the 
  Petri 
  dish 
  the 
  stender 
  dish 
  

   containing 
  the 
  manure 
  was 
  then 
  placed 
  in 
  the 
  Petri 
  dish 
  on 
  the 
  small 
  pool 
  of 
  milk. 
  

   This 
  had 
  the 
  effect 
  of 
  pressing 
  the 
  milk 
  out 
  to 
  the 
  edge 
  of 
  the 
  bottom 
  of 
  the 
  stender 
  

   dish, 
  where 
  it 
  was 
  deposited 
  in 
  a 
  narrow 
  ring, 
  being 
  of 
  such 
  small 
  quantity 
  that 
  it 
  

   was 
  practically 
  held 
  in 
  place 
  by 
  capillary 
  attraction. 
  

  

  The 
  principal 
  merits 
  of 
  applying 
  the 
  milk 
  in 
  this 
  manner 
  was 
  that 
  it 
  eliminated 
  

   the 
  use 
  of 
  a 
  second 
  container 
  within 
  the 
  globe 
  and 
  left 
  ample 
  space 
  for 
  the 
  flies 
  to 
  

   move 
  about 
  on 
  the 
  Petri 
  dish 
  between 
  the 
  stender 
  dish 
  and 
  the 
  edge 
  of 
  the 
  globe. 
  

   Furthermore, 
  the 
  ring 
  of 
  milk 
  being 
  so 
  small 
  and 
  situated 
  as 
  it 
  was 
  they 
  could 
  feed 
  

   on 
  it 
  but 
  could 
  not 
  fall 
  into 
  it 
  and 
  become 
  wet 
  and 
  bedraggled, 
  which 
  would 
  have 
  

   hastened 
  their 
  death. 
  It 
  is 
  believed 
  that 
  the 
  greater 
  part 
  of 
  the 
  success 
  in 
  preventing 
  

   early 
  mortality 
  among 
  the 
  flies, 
  and 
  in 
  securing 
  the 
  repeated 
  depositions 
  and 
  large 
  

   numbers 
  of 
  eggs, 
  was 
  due 
  to 
  the 
  use 
  of 
  lantern 
  globes 
  for 
  breeding-jars 
  in 
  place 
  of 
  

   wire 
  cages 
  and 
  in 
  the 
  manner 
  of 
  administering 
  the 
  milk 
  and 
  manure. 
  

  

  The 
  globes 
  containing 
  the 
  flies 
  were 
  arranged 
  near 
  a 
  window 
  in 
  such 
  a 
  way 
  that 
  

   some 
  of 
  them 
  were 
  exposed 
  to 
  the 
  bright 
  sunlight 
  practically 
  all 
  of 
  each 
  day, 
  others 
  

   during 
  part 
  of 
  each 
  day 
  only 
  and 
  the 
  remainder 
  in 
  the 
  shade 
  at 
  all 
  times 
  and 
  receiving 
  

   no 
  sunlight. 
  However, 
  no 
  appreciable 
  difference 
  was 
  observed 
  in 
  the 
  number 
  or 
  

   frequency 
  of 
  depositions 
  or 
  the 
  number 
  of 
  eggs 
  deposited 
  between 
  those 
  exposed 
  to 
  

   the 
  sunlight 
  and 
  those 
  that 
  were 
  in 
  the 
  shade, 
  although 
  a 
  slight 
  difference 
  of 
  tempera- 
  

   ture 
  and 
  humidity 
  possibly 
  existed 
  at 
  times. 
  It 
  was 
  noticed 
  that 
  the 
  milk 
  and 
  

   manure 
  dried 
  up 
  more 
  quickly 
  in 
  the 
  globes 
  that 
  were 
  exposed 
  to 
  the 
  sunlight, 
  which 
  

   was 
  to 
  be 
  expected. 
  

  

  Throughout 
  these 
  observations 
  the 
  globes 
  were 
  examined 
  three 
  times 
  daily. 
  

   These 
  examinations 
  occurred 
  between 
  8 
  to 
  12 
  a.m., 
  2 
  to 
  6 
  p.m., 
  and 
  8 
  to 
  12 
  p.m. 
  

   Thus 
  the 
  only 
  period 
  during 
  which 
  no 
  check 
  was 
  made 
  was 
  from 
  midnight 
  to 
  8 
  a.m. 
  

  

  At 
  each 
  examination 
  the 
  globe 
  was 
  lifted 
  slightly 
  from 
  the 
  Petri 
  dish 
  and 
  a 
  piece 
  

   of 
  cardboard 
  slipped 
  underneath 
  to 
  prevent 
  the 
  flies 
  from 
  escaping. 
  The 
  stender 
  

   dish 
  containing 
  the 
  manure 
  was 
  removed 
  and 
  the 
  Petri 
  dish 
  washed 
  clean 
  of 
  all 
  milk 
  

   and 
  dried 
  well. 
  Fresh 
  milk 
  was 
  dropped 
  in 
  the 
  centre 
  again 
  and 
  a 
  clean 
  stender 
  

   dish 
  containing 
  fresh 
  manure 
  was 
  placed 
  in 
  the 
  milk. 
  After 
  removing 
  the 
  cardboard 
  

   from 
  the 
  bottom 
  of 
  the 
  globe 
  the 
  latter 
  was 
  then 
  replaced 
  on 
  the 
  Petri 
  dish. 
  The 
  

   manure 
  taken 
  from 
  each 
  globe 
  was 
  then 
  carefully 
  inspected, 
  being 
  teased 
  into 
  small 
  

   shreds, 
  and 
  all 
  eggs 
  found 
  were 
  removed 
  and 
  counted 
  with 
  the 
  aid 
  of 
  a 
  hand 
  lens 
  

   and 
  a 
  blunt 
  dissecting 
  needle, 
  the 
  latter 
  being 
  used 
  to 
  separate 
  them. 
  After 
  being 
  

   counted 
  they 
  were 
  placed 
  in 
  a 
  second 
  piece 
  of 
  manure 
  until 
  the 
  larvae 
  emerged 
  as 
  

   a 
  test 
  for 
  fertility. 
  

  

  (8053) 
  x 
  

  

  