﻿GENEALOGY 
  OF 
  INSECTS. 
  297 
  

  

  y. 
  Memiptera. 
  — 
  The 
  only 
  clew 
  to 
  the 
  origin 
  of 
  this 
  well 
  circumscribed 
  

   order 
  is 
  the 
  fact 
  that 
  in 
  the 
  Physapoda 
  (Thrips) 
  and 
  the 
  Mallophaga 
  

   the 
  mandibles 
  are 
  free 
  and 
  adapted 
  for 
  biting. 
  This 
  would 
  indicate 
  that 
  

   the 
  entire 
  group 
  was 
  derived 
  from 
  ancestors 
  allied 
  possibly 
  to 
  the 
  Phy- 
  

   loptera. 
  The 
  Mallophaga 
  are 
  by 
  different 
  authors 
  referred 
  to 
  the 
  Or- 
  

   thoptera 
  and 
  Neuropter^, 
  but 
  the 
  development 
  of 
  the 
  bird-lice 
  as 
  worked 
  

   out 
  by 
  Melnikow 
  fully 
  proves 
  that 
  in 
  the 
  form 
  of 
  the 
  egg, 
  the 
  mode 
  of 
  de- 
  

   velopment, 
  and 
  general 
  form 
  of 
  the 
  embryo, 
  the 
  Parasita 
  and 
  Mallophaga 
  

   travel 
  along 
  the 
  same 
  developmental 
  path 
  until 
  just 
  before 
  hatching, 
  

   when 
  in 
  Mallophaga 
  the 
  jaws 
  remain 
  free, 
  while 
  in 
  the 
  Parasita 
  they 
  be- 
  

   come 
  farther 
  modified 
  and 
  form 
  a 
  sucking 
  beak. 
  

  

  There 
  is 
  a 
  possibility 
  that 
  the 
  Hemiptera 
  may 
  have 
  descended 
  from 
  in- 
  

   sects 
  remotely 
  allied 
  to 
  the 
  Pseudoneuroptera 
  : 
  perhaps 
  forms 
  resembling 
  

   the 
  PsocidsBj 
  at 
  least 
  this 
  family, 
  the 
  wingless 
  forms 
  of 
  which 
  superfi- 
  

   cially 
  resemble 
  the 
  Mallophaga, 
  gives 
  hints 
  which 
  may 
  throw 
  light 
  on 
  

   the 
  origin 
  of 
  the 
  Hemiptera. 
  They 
  are 
  evidently 
  the 
  offshoot 
  of 
  a 
  stock 
  

   which 
  had 
  an 
  incomplete 
  metamorphosis, 
  or 
  they 
  may 
  have 
  descended 
  

   directly 
  from 
  a 
  modified 
  Oampodea-like 
  ancestral 
  form. 
  

  

  YL 
  JSfeuroptera. 
  — 
  The 
  members 
  of 
  this 
  order 
  are, 
  excepting 
  perhaps 
  

   the 
  Hemiptera, 
  the 
  most 
  modern 
  and 
  least 
  composite 
  or 
  synthetic 
  forms 
  

   that 
  we 
  have 
  yet 
  met 
  with 
  in 
  our 
  ascent 
  up 
  the 
  insect 
  series 
  from 
  the 
  

   Thysanura. 
  Moreover, 
  in 
  them 
  for 
  the 
  first 
  time 
  do 
  we 
  meet 
  with 
  worm- 
  

   like, 
  cylindrical-bodied 
  larvse, 
  or 
  what 
  we 
  have 
  called 
  cruciform 
  larvse.^''^ 
  

   These 
  larvge 
  are 
  secondary 
  forms, 
  derived, 
  as 
  Fritz 
  Milller 
  has 
  in 
  a 
  gen- 
  

   eral 
  way 
  suggested, 
  from 
  those 
  larvse 
  which 
  have 
  an 
  incomplete 
  metamor- 
  

   phosis. 
  By 
  what 
  line 
  of 
  descent, 
  however, 
  the 
  lowest 
  group 
  of 
  Neuro- 
  

   ptera, 
  viz., 
  the 
  Sialidse, 
  arose, 
  it 
  would 
  be 
  difficult 
  to 
  say. 
  The 
  earliest 
  

   winged 
  insects 
  were 
  probably 
  terrestrial 
  5 
  the 
  aquatic 
  larval 
  forms 
  of 
  the 
  

   SialidsB 
  are 
  evidently 
  derivations 
  from 
  Oampodea-like 
  terrestrial 
  larvae. 
  

   But 
  how 
  the 
  perfect 
  metamorphosis 
  with 
  the 
  quiescent 
  pupa 
  of 
  the 
  Neu- 
  

   roptera 
  was 
  brought 
  about, 
  is 
  indeed 
  a 
  problem. 
  It 
  is 
  evident, 
  however, 
  

   that 
  the 
  cruciform 
  larva 
  is 
  a 
  derivation 
  from 
  a 
  Thysanuriform 
  ^^^ 
  type, 
  

   first 
  stated 
  by 
  Fritz 
  MtLller. 
  

  

  It 
  seems 
  to 
  us 
  that 
  a 
  consideration 
  of 
  the 
  diverse 
  larval 
  forms 
  which 
  

   occur 
  in 
  the 
  present 
  order, 
  throws 
  some 
  light 
  on 
  the 
  origin 
  of 
  a 
  com- 
  

   plete 
  metamorphosis 
  in 
  insects 
  in 
  general. 
  In 
  the 
  Sialidse, 
  as 
  the 
  larva 
  

   of 
  Corydalus, 
  or 
  Semblis, 
  we 
  have 
  a 
  Campodea-form 
  provided 
  with 
  gills, 
  

   and 
  with 
  the 
  mouth-parts 
  adapted 
  for 
  seizing 
  and 
  biting 
  its 
  prey. 
  The 
  

   terrestrial 
  larvse 
  of 
  the 
  Hemerobiidse 
  are 
  evidently 
  modifications 
  of 
  the 
  

   Sialid 
  larval 
  form; 
  the 
  differences 
  of 
  structure 
  in 
  them, 
  such 
  as 
  the 
  long, 
  

  

  "5 
  See 
  "Our 
  Common 
  Insects," 
  p. 
  175, 
  1873. 
  Also 
  the 
  Ameriean 
  Naturalist, 
  vol. 
  V, 
  Sept. 
  1871. 
  

  

  146 
  -^e 
  have 
  in 
  the 
  writings 
  just 
  quoted 
  called 
  the 
  second 
  class 
  of 
  larvae 
  Leptiform, 
  but 
  the 
  term 
  

   Thysanuriform, 
  or 
  Brauer's 
  expression 
  Campodea-form, 
  is 
  preferable. 
  The 
  Campodea 
  or 
  primitive 
  

   Hexapodous 
  form 
  is 
  evidently 
  a 
  derivative 
  form, 
  which 
  points 
  back 
  to 
  a 
  common 
  six-footed 
  ancestor 
  of 
  

   all 
  Tracheata, 
  to 
  which 
  the 
  term 
  Leptiform 
  may 
  he 
  applied. 
  

  

  