﻿SCALE 
  INSECTS 
  OF 
  IMPORTANCE 
  345 
  

  

  speak 
  of 
  them 
  simply 
  as 
  the 
  ventral 
  glands. 
  They 
  appear 
  only 
  in 
  the 
  

   adult 
  female 
  aiid 
  not 
  in 
  all 
  species. 
  They 
  are 
  of 
  rather 
  special 
  interest 
  

   in 
  economic 
  study 
  because 
  their 
  presence 
  at 
  once 
  proves 
  the 
  specimen 
  to 
  

   be 
  something 
  other 
  than 
  the 
  pernicious 
  or 
  San 
  Jose 
  scale, 
  though 
  their 
  

   absence 
  does 
  not 
  necessarily 
  indicate 
  the 
  contrary. 
  Once 
  seen 
  they 
  are 
  

   easily 
  recognized, 
  for 
  no 
  other 
  organ 
  resembles 
  them 
  in 
  their 
  definite 
  

   circular 
  outline 
  and 
  in 
  the 
  manner 
  of 
  grouping 
  (pi. 
  ii, 
  fig. 
  i 
  g, 
  g). 
  In 
  

   the 
  genus 
  Aspidiotus 
  there 
  are 
  usually 
  four 
  or 
  five 
  groups 
  when 
  pres- 
  

   ent 
  at 
  all. 
  The 
  groups 
  are 
  then 
  spoken 
  of 
  as 
  the 
  anterior 
  or 
  cephalo- 
  

   laterals, 
  and 
  the 
  posterior, 
  or 
  caudo-laterals, 
  while 
  the 
  fifth 
  group 
  when 
  

   present 
  is 
  anterior 
  and 
  median 
  and 
  is 
  called 
  by 
  the 
  one 
  or 
  the 
  other 
  of 
  

   these 
  terms. 
  

  

  In 
  the 
  region 
  of 
  the 
  lateral 
  ventral 
  glands 
  the 
  body 
  wall 
  is 
  thickened 
  

   (pi. 
  II, 
  fig. 
  ih). 
  These 
  are 
  the 
  ventral 
  chitinous 
  thickenings, 
  and 
  are 
  to 
  

   a 
  certain 
  degree 
  characteristic. 
  In 
  A. 
  ancylus 
  and 
  A. 
  ostreae- 
  

   f 
  o 
  r 
  m 
  i 
  s 
  they 
  are 
  somewhat 
  indefinite 
  and 
  appear 
  as 
  if 
  folded 
  or 
  crum- 
  

   pled, 
  in 
  A. 
  forbesi 
  they 
  are 
  nearly 
  straight, 
  narrow 
  and 
  definite, 
  being 
  

   spoken 
  of 
  in 
  the 
  original 
  description 
  as 
  "club-shaped 
  organs 
  about 
  which 
  

   the 
  spinnerets 
  are 
  grouped." 
  In 
  A. 
  perniciosus 
  also 
  they 
  are 
  more 
  

   definite 
  than 
  in 
  A. 
  ancylus 
  and 
  A. 
  os 
  treaeformis 
  , 
  though 
  not 
  so 
  

   straight 
  nor 
  so 
  narrow 
  as 
  in 
  A. 
  forbesi, 
  and 
  they 
  appear 
  distinct 
  and 
  

   dark 
  in 
  the 
  adult 
  female 
  even 
  when 
  the 
  eggs 
  or 
  young 
  are 
  not 
  present 
  to 
  

   prove 
  the 
  species. 
  This 
  distinguishes 
  the 
  adult 
  but 
  not 
  yet 
  gravid 
  A. 
  

   perniciosus 
  from 
  the 
  immature 
  specimens 
  of 
  the 
  four 
  species, 
  because 
  

   in 
  the 
  first 
  and 
  second 
  stages 
  of 
  all 
  four 
  these 
  thickenings, 
  though 
  indi- 
  

   cated, 
  are 
  small 
  and 
  indefinite, 
  practically 
  parenthesis-shaped 
  and 
  quite 
  

   different 
  from 
  the 
  third 
  stage 
  appearance. 
  Reference 
  to 
  the 
  figures 
  will 
  

   make 
  these 
  statements 
  perfectly 
  clear, 
  I 
  think. 
  

  

  The 
  vagina 
  may 
  sometimes 
  be 
  detected 
  as 
  a 
  tranverse 
  opening 
  about 
  

   the 
  middle 
  of 
  the 
  plate 
  on 
  the 
  ventral 
  side 
  (pi. 
  ii, 
  fig. 
  ij). 
  It 
  does 
  

   not 
  in 
  general 
  serve 
  in 
  classification, 
  and 
  I 
  have 
  not 
  figured 
  it 
  under 
  the 
  

   different 
  species. 
  

  

  The 
  dorsal 
  aspect 
  is 
  marked 
  near 
  the 
  base 
  of 
  the 
  segment 
  in 
  the 
  following 
  

   species 
  by 
  four, 
  transverse 
  chitinous 
  thickenings, 
  two 
  lateral 
  and 
  two 
  

   median 
  (pi. 
  ii, 
  fig. 
  i 
  k, 
  k). 
  Occasionally 
  there 
  are 
  two 
  fainter 
  longi- 
  

   tudinal 
  markings 
  of 
  chitin 
  parallel 
  and 
  near 
  the 
  middle 
  of 
  the 
  segment. 
  

  

  There 
  are 
  also 
  on 
  the 
  dorsal 
  aspect 
  oval 
  openings 
  of 
  more 
  or 
  less 
  

   prominence 
  in 
  different 
  species, 
  which 
  are 
  perhaps 
  most 
  simply 
  designated 
  

   the 
  dorsal 
  pores. 
  I 
  have 
  shown 
  different 
  appearances 
  of 
  these 
  seen 
  in 
  

   focusing 
  in 
  plate 
  ii, 
  figure 
  i 
  /, 
  /. 
  In 
  some 
  species 
  they 
  are 
  numerous 
  and 
  

  

  