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  64- 
  

  

  ov 
  the 
  mechanical 
  mixture 
  with 
  water 
  already 
  referred 
  to 
  on 
  page 
  53. 
  

   This 
  might 
  perhaps 
  be 
  successfully 
  applied 
  by 
  a 
  simple 
  apparatus 
  

   recommended 
  by 
  Professor 
  John 
  B. 
  Smith 
  for 
  the 
  destruction 
  of 
  leaf- 
  

   hoppers 
  in 
  potato 
  fields. 
  Four 
  nozzles 
  suitable 
  for 
  producing 
  a 
  fine 
  

   profuse 
  spray 
  are 
  carried 
  on 
  a 
  horizontal 
  bar 
  suspended 
  from 
  the 
  back 
  

   of 
  the 
  wagon, 
  the 
  nozzles 
  being 
  directed 
  forward 
  and 
  a 
  little 
  downward. 
  

   A 
  light 
  board 
  is 
  hung 
  three 
  or 
  four 
  feet 
  in 
  front 
  of 
  thQ 
  horizontal 
  bar 
  to 
  

   stir 
  up 
  the 
  leaf-hoppers 
  and 
  expose 
  them 
  to 
  the 
  fine 
  kerosene 
  spray 
  with 
  

   which 
  the 
  air 
  is 
  filled. 
  Arsenical 
  insecticides 
  would 
  of 
  course 
  be 
  with- 
  

   out 
  important 
  effect, 
  since 
  these 
  are 
  internal 
  poisons 
  and 
  could 
  not 
  

   reach 
  the 
  digestive 
  organs 
  of 
  a 
  sucking 
  insect. 
  

  

  The 
  general 
  aspect 
  of 
  the 
  leaf-hoppers 
  may 
  be 
  easily 
  recognized 
  

   after 
  an 
  examination 
  of 
  the 
  various 
  figures 
  in 
  this 
  text. 
  There 
  is 
  no 
  

   special 
  economic 
  value 
  in 
  a 
  discrimination 
  of 
  the 
  numerous 
  species 
  in- 
  

   festing 
  the 
  beet 
  or 
  in 
  the 
  details 
  of 
  the 
  life 
  history 
  of 
  each, 
  but 
  these 
  

   will 
  nevertheless 
  have 
  a 
  certain 
  general 
  utility 
  as 
  an 
  aid 
  to 
  observation 
  

   and 
  record 
  by 
  economic 
  entomologists, 
  and 
  an 
  attempt 
  is 
  therefore 
  

   made 
  here 
  to 
  give 
  the 
  most 
  conspicuous 
  distinctions 
  of 
  each 
  group 
  

   without 
  entering 
  into 
  difficult 
  structural 
  details. 
  

  

  It 
  will 
  first 
  be 
  necessary 
  to 
  separate 
  the 
  leaf 
  hoppers 
  known 
  to 
  infest 
  

   the 
  beet 
  into 
  four 
  groups, 
  distinguished 
  in 
  part 
  by 
  the 
  position 
  of 
  the 
  

   bead-like 
  ocelli 
  which 
  always 
  lie 
  somewhere 
  between 
  the 
  compound 
  

   eyes. 
  

  

  The 
  first 
  group 
  (PI. 
  I.), 
  belonging 
  to 
  the 
  family 
  Fulgoridic, 
  subfamily 
  

   Delphacince, 
  are 
  small, 
  witli 
  clear 
  membranous 
  wings 
  bearing 
  various 
  

   dark 
  markings. 
  The 
  head 
  and 
  thorax 
  are 
  acutely 
  ridged, 
  and 
  the 
  

   antenn;i3 
  have 
  a 
  stout 
  finger-like 
  base, 
  with 
  a 
  thread-like 
  terminal 
  bristle. 
  

   The 
  ocelli 
  are 
  close 
  in 
  front 
  of 
  the 
  lower 
  angle 
  of 
  the 
  compound 
  eyes, 
  

   and 
  there 
  is'a 
  conspicuous 
  movable 
  spine 
  at 
  the 
  tip 
  of 
  the 
  hind 
  tibia. 
  

   The 
  same 
  species 
  sometimes 
  presents 
  both 
  long-winged 
  and 
  short- 
  

   winged 
  forms. 
  

  

  The 
  remaining 
  groups 
  belong 
  to 
  the 
  superfamily 
  Jassoidca, 
  with 
  

   opaque 
  or 
  tinted 
  wings, 
  the 
  antennal 
  bristle 
  rising 
  from 
  a 
  merely 
  thick- 
  

   ened 
  base, 
  and 
  the 
  ocelli 
  higher 
  up 
  on 
  the 
  head. 
  In 
  the 
  second 
  group 
  

   (Fig. 
  5-7) 
  the 
  species 
  of 
  Agallia 
  only 
  are 
  included. 
  These 
  are 
  small 
  

   brownish 
  strongly 
  wedge-shaped 
  insects, 
  with 
  head 
  obtuse 
  in 
  front, 
  and 
  

   the 
  ocelli 
  well 
  up 
  on 
  tlie 
  face 
  but 
  below 
  the 
  front 
  margin 
  of 
  the 
  head. 
  

  

  The 
  third 
  group 
  (Fig. 
  8, 
  9) 
  includes 
  the 
  large 
  species 
  treated 
  in 
  this 
  

   paper, 
  those 
  belonging 
  to 
  Onconietopia, 
  Diedrocepliala, 
  and 
  Gypona. 
  

   They 
  range 
  from 
  three-sixteenths 
  to 
  half 
  an 
  inch 
  in 
  length. 
  The 
  most 
  

   distinctive 
  characteristic 
  is 
  the 
  position 
  of 
  the 
  ocelli_ 
  wliich 
  are 
  on 
  the 
  

   flat 
  top 
  of 
  the 
  head, 
  between 
  the 
  eyes. 
  

  

  The 
  fourth 
  group 
  (Fig. 
  10, 
  11; 
  PI. 
  II.; 
  PI. 
  III., 
  Fig. 
  i, 
  2) 
  contains 
  a 
  

   large 
  number 
  of 
  species, 
  nearly 
  all 
  quite 
  small 
  and 
  variously 
  colored. 
  

  

  