﻿346 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  prominent, 
  in 
  others 
  not 
  nearly 
  so 
  much 
  so. 
  They 
  are 
  perhaps 
  openings 
  

   of 
  glands 
  which 
  assist 
  in 
  the 
  formation 
  of 
  the 
  scale. 
  Among 
  these 
  are 
  

   seen 
  curious 
  organs 
  which 
  may 
  seem 
  to 
  be 
  on 
  the 
  surface 
  of 
  the 
  body 
  

   but 
  are 
  proved 
  by 
  focusing 
  to 
  occur 
  within 
  it 
  in 
  connection 
  with 
  external 
  

   openings. 
  These 
  have 
  been 
  denominated 
  by 
  Prof 
  Comstock 
  the 
  wax 
  

   ducts. 
  In 
  the 
  explanatory 
  figure 
  a 
  few 
  are 
  represented 
  at 
  ;;/, 
  m, 
  but 
  not 
  

   in 
  later 
  figures, 
  as 
  they 
  have 
  not 
  been 
  shown 
  to 
  have 
  definiteness 
  ot 
  

   arrangement 
  or 
  classificatory 
  value. 
  

  

  The 
  large 
  circular 
  opening 
  on 
  the 
  dorsal 
  side 
  is 
  the 
  anus 
  (pi. 
  ii, 
  fig. 
  

   \n). 
  Like 
  the 
  other 
  dorsal 
  organs 
  it 
  is 
  visible 
  from 
  the 
  ventral 
  side 
  also, 
  

   appearing 
  as 
  a 
  clear 
  area. 
  

  

  I 
  think 
  no 
  other 
  organs 
  of 
  importance 
  are 
  present 
  in 
  the 
  four 
  species 
  

   here 
  mentioned. 
  There 
  are 
  sometimes 
  visible 
  a 
  few 
  minute 
  round 
  pores 
  

   and 
  some 
  small 
  superficial 
  spines, 
  or 
  hairs, 
  but 
  they 
  may 
  be 
  disregarded. 
  

  

  Distinguishing 
  species. 
  It 
  is 
  of 
  course 
  a 
  commonplace 
  in 
  many 
  

   divisions 
  of 
  science, 
  but 
  perhaps 
  in 
  none 
  more 
  than 
  in 
  the 
  study 
  of 
  the 
  

   Coccidae, 
  that 
  famiUarity 
  with 
  forms 
  is 
  necessary 
  for 
  any 
  great 
  degree 
  

   of 
  certainty 
  in 
  determining 
  species. 
  Descriptions 
  of 
  two 
  or 
  three 
  different 
  

   species 
  read 
  marvelously 
  alike, 
  and 
  even 
  figures 
  are 
  not 
  absolutely 
  dis- 
  

   tinctive, 
  because 
  of 
  the 
  great 
  variabihty 
  in 
  species. 
  Moreover, 
  the 
  

   untrained 
  eye 
  does 
  not 
  quickly 
  recognize 
  differences, 
  specially 
  where 
  dis- 
  

   tinctions 
  must 
  be 
  largely 
  comparative. 
  Hence 
  any 
  key 
  to 
  species 
  must 
  

   in 
  the 
  nature 
  of 
  things 
  be 
  unsatisfactory, 
  for 
  it 
  must 
  be 
  relative 
  in 
  its 
  

   terms 
  and 
  so 
  can 
  not 
  be 
  used 
  with 
  large 
  degree 
  of 
  certainty 
  in 
  each 
  step 
  

   till 
  famiharity 
  with 
  the 
  species 
  renders 
  it 
  unnecessary. 
  However, 
  it 
  is 
  

   sometimes 
  an 
  aid 
  in 
  earlier 
  studies 
  through 
  its 
  emphasis 
  of 
  the 
  more 
  dis- 
  

   tinctive 
  features, 
  and 
  the 
  following 
  is 
  submitted 
  with 
  that 
  end 
  in 
  view. 
  

   It 
  applies 
  only 
  to 
  the 
  four 
  species 
  here 
  farther 
  characterized, 
  and 
  per- 
  

   haps 
  may 
  not 
  exclude 
  other 
  species, 
  which 
  have 
  not 
  fallen 
  under 
  my 
  

   ken, 
  so 
  that 
  it 
  will 
  be 
  useful 
  only 
  when 
  the 
  student 
  finds 
  it 
  probable 
  that 
  

   he 
  has 
  one 
  of 
  these 
  four, 
  but 
  is 
  not 
  sure 
  which 
  one. 
  They 
  are 
  the 
  four 
  

   species 
  of 
  Aspidiotus 
  most 
  frequently 
  brought 
  to 
  the 
  attention 
  of 
  

   horticulturists 
  in 
  this 
  state, 
  a 
  fact 
  which 
  may 
  justify 
  this 
  fimitation 
  of 
  

   my 
  study. 
  

  

  This 
  key 
  will 
  apply, 
  I 
  think, 
  to 
  the 
  second 
  stages 
  as 
  well 
  as 
  to 
  the 
  

   mature 
  females, 
  though 
  with 
  hardly 
  as 
  much 
  positiveness. 
  I 
  have 
  been 
  

   unable 
  to 
  detect 
  constant 
  specific 
  differences 
  in 
  forms 
  before 
  the 
  first 
  

   molt. 
  Sometimes 
  the 
  question 
  may 
  arise 
  as 
  to 
  whether 
  the 
  form 
  pre- 
  

   sented 
  is 
  adult 
  or 
  not. 
  This 
  occurs 
  when 
  neither 
  ventral 
  glands 
  nor 
  

   eggs 
  nor 
  young 
  are 
  present. 
  In 
  this 
  case 
  if 
  the 
  ventral 
  thickenings 
  are 
  

  

  