﻿302 
  L. 
  H. 
  DUNN. 
  

  

  batch 
  of 
  eggs, 
  which 
  process 
  it 
  repeats 
  at 
  intervals 
  of 
  ten 
  to 
  fourteen 
  days, 
  till 
  four 
  

   batches 
  have 
  been 
  laid, 
  when 
  it 
  dies.' 
  Our 
  observations 
  indicate 
  that 
  in 
  Texas 
  

   fewer 
  batches 
  of 
  eggs, 
  the 
  usual 
  number 
  being 
  two, 
  are 
  deposited 
  and 
  that 
  depositions 
  

   take 
  place 
  at 
  shorter 
  intervals 
  — 
  about 
  eight 
  days." 
  

  

  Howard 
  and 
  Hutchison* 
  state, 
  " 
  The 
  number 
  of 
  eggs 
  laid 
  by 
  an 
  individual 
  fly 
  

   at 
  one 
  time 
  undoubtedly 
  is 
  large, 
  probably 
  averaging 
  about 
  120, 
  and 
  as 
  a 
  single 
  

   female 
  will 
  lay 
  at 
  least 
  two 
  and 
  possibly 
  four 
  such 
  batches, 
  the 
  enormous 
  numbers 
  

   in 
  which 
  the 
  insects 
  occur 
  are 
  thus 
  plainly 
  accounted 
  for 
  . 
  . 
  . 
  ." 
  

  

  In 
  1918, 
  while 
  engaged 
  in 
  carrying 
  on 
  some 
  experiments 
  with 
  the 
  house-fly 
  in 
  

   the 
  Canal 
  Zone, 
  the 
  writer 
  conducted 
  a 
  series 
  of 
  observations 
  on 
  the 
  oviposition 
  

   habits 
  in 
  order 
  to 
  obtain 
  more 
  definite 
  information 
  on 
  this 
  phase 
  of 
  the 
  biology 
  of 
  

   M. 
  domestica 
  in 
  the 
  American 
  tropics. 
  The 
  oviposition 
  by 
  individual 
  flies 
  was 
  

   found 
  to 
  be 
  so 
  much 
  greater 
  than 
  has 
  been 
  supposed 
  heretofore, 
  that 
  the 
  results 
  are 
  

   deemed 
  worthy 
  of 
  report. 
  

  

  At 
  the 
  beginning 
  of 
  our 
  observations 
  groups 
  of 
  flies 
  confined 
  together 
  in 
  large 
  

   cages 
  were 
  used, 
  but 
  this 
  method 
  was 
  soon 
  found 
  to 
  be. 
  unsatisfactory 
  and 
  conse- 
  

   quently 
  discarded. 
  It 
  became 
  early 
  apparent 
  that 
  the 
  only 
  accurate 
  data 
  obtainable 
  

   by 
  this 
  method 
  was 
  the 
  length 
  of 
  the 
  pre-oviposition 
  period 
  of 
  the 
  first 
  females 
  in 
  

   the 
  group 
  that 
  oviposited. 
  After 
  the 
  first 
  batch 
  of 
  eggs 
  was 
  deposited 
  it 
  was 
  quite 
  

   impossible 
  to 
  determine 
  with 
  any 
  degree 
  of 
  accuracy 
  the 
  origin 
  of 
  the 
  following 
  batches, 
  

   whether 
  but 
  a 
  few 
  females 
  were 
  depositing 
  at 
  frequent 
  intervals 
  or 
  a 
  greater 
  number 
  

   at 
  longer 
  intervals. 
  Thus 
  becoming 
  convinced 
  of 
  the 
  fact 
  that 
  the 
  data 
  obtained 
  by 
  

   using 
  groups 
  of 
  flies 
  would 
  consist 
  more 
  of 
  assumed 
  conclusions 
  than 
  of 
  definite 
  and 
  

   dependable 
  facts, 
  it 
  was 
  decided 
  to 
  use 
  isolated 
  pairs 
  of 
  flies 
  in 
  making 
  the 
  observations. 
  

  

  After 
  experimenting 
  with 
  several 
  kinds 
  of 
  small 
  cages 
  and 
  glass 
  jars, 
  none 
  of 
  which 
  

   proved 
  satisfactory, 
  Dietz 
  lantern 
  globes, 
  as 
  used 
  in 
  former 
  mosquito-breeding 
  

   work, 
  were 
  tried 
  and 
  found 
  to 
  be 
  very 
  suitable. 
  The 
  technique 
  of 
  conducting 
  the 
  

   experiments 
  was 
  as 
  follows 
  : 
  — 
  Fly 
  larvae 
  were 
  obtained 
  from 
  three 
  sources, 
  the 
  city 
  

   dump 
  at 
  Panama, 
  a 
  compost 
  pit 
  at 
  Corozal, 
  about 
  two 
  miles 
  distant 
  from 
  Panama, 
  

   and 
  a 
  laboratory 
  strain 
  that 
  had 
  been 
  reared 
  through 
  several 
  generations, 
  thus 
  giving 
  

   what 
  would 
  apparently 
  be 
  three 
  different 
  strains. 
  After 
  being 
  collected 
  the 
  larvae 
  

   were 
  placed 
  in 
  fresh 
  horse 
  manure 
  and 
  allowed 
  to 
  remain 
  until 
  pupation, 
  when 
  they 
  

   were 
  removed 
  and 
  placed 
  singly 
  in 
  test-tubes, 
  which 
  were 
  then 
  stoppered 
  with 
  tight 
  

   cotton 
  plugs. 
  

  

  The 
  pupae 
  were 
  closely 
  observed, 
  and 
  as 
  soon 
  as 
  the 
  adults 
  appeared 
  they 
  were 
  

   separated 
  in 
  pairs 
  and 
  transferred 
  to 
  the 
  lantern 
  globes, 
  one 
  pair 
  to 
  a 
  globe. 
  Each 
  

   globe 
  had 
  its 
  upper, 
  or 
  smaller, 
  end 
  covered 
  with 
  a 
  piece 
  of 
  cotton 
  gauze, 
  held 
  in 
  

   place 
  with 
  strips 
  of 
  adhesive 
  tape. 
  A 
  circular 
  ring 
  of 
  thin 
  cardboard 
  placed 
  within 
  

   each 
  globe 
  at 
  its 
  largest 
  part 
  afforded 
  a 
  resting 
  place 
  for 
  the 
  flies. 
  Each 
  globe 
  was 
  

   placed, 
  large 
  end 
  downward, 
  in 
  a 
  shallow 
  Petri 
  dish 
  of 
  sufficient 
  diameter 
  to 
  allow 
  

   the 
  bottom 
  of 
  the 
  globe 
  to 
  set 
  in 
  it 
  without 
  much 
  space 
  being 
  left. 
  

  

  Milk 
  and 
  horse 
  manure 
  were 
  used 
  throughout 
  the 
  observations, 
  the 
  former 
  as 
  

   food 
  for 
  the 
  flies 
  and 
  the 
  latter 
  as 
  material 
  in 
  which 
  to 
  deposit 
  their 
  eggs. 
  The 
  

   choosing 
  of 
  these 
  two 
  substances 
  was 
  due 
  to 
  the 
  fact 
  that 
  milk 
  is 
  not 
  only 
  strongly 
  

   attractive 
  to 
  flies, 
  but 
  also 
  contains 
  nearly 
  all 
  of 
  the 
  necessary 
  food 
  elements, 
  and 
  

   manure, 
  when 
  available 
  under 
  natural 
  conditions, 
  usually 
  seems 
  to 
  be 
  the 
  favourite 
  

   nidus 
  in 
  which 
  to 
  deposit 
  their 
  eggs. 
  

  

  Considerable 
  care 
  was 
  taken 
  in 
  order 
  to 
  avoid 
  using 
  manure 
  that 
  was 
  already 
  

   infested. 
  It 
  was 
  collected 
  fresh 
  each 
  morning 
  at 
  the 
  corral, 
  usually 
  being 
  taken 
  

  

  * 
  Howard, 
  L. 
  O., 
  and 
  Hutchison, 
  R. 
  H. 
  " 
  The 
  House 
  Fly." 
  U.S. 
  Dept. 
  of 
  Agric, 
  Farmers' 
  

   Bull. 
  679, 
  Aug. 
  1917, 
  p. 
  6. 
  

  

  