﻿300 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  tainty 
  the 
  line 
  of 
  development 
  of 
  this 
  extensive 
  order 
  from 
  the 
  Gam- 
  

   podea 
  type. 
  There 
  are 
  two 
  series 
  of 
  facts 
  which 
  seem 
  to 
  us 
  to 
  throw 
  

   light 
  on 
  the 
  subject. 
  

  

  First, 
  the 
  form 
  of 
  the 
  free, 
  active 
  larvae 
  of 
  the 
  carnivorous 
  groups 
  of 
  

   beetles. 
  The 
  larvae 
  of 
  the 
  Oarabidae, 
  Dytiscidae 
  and 
  Staphylinidae 
  appear 
  

   to 
  us 
  to 
  be 
  on 
  the 
  whole 
  more 
  nearly 
  allied 
  to 
  what 
  was 
  probably 
  the 
  pri 
  mi- 
  

   tive 
  form 
  of 
  Coleopterous 
  larva 
  than 
  those 
  of 
  any 
  other 
  fa.milies. 
  This 
  

   ancestral 
  Coleopterous 
  larva 
  was 
  probably 
  directly 
  related 
  to 
  the 
  Campo- 
  

   dea-form 
  ancestor 
  of 
  the 
  Hexapoda. 
  The 
  general 
  form 
  of 
  the 
  body, 
  the 
  

   homonomous 
  segments, 
  the 
  free, 
  biting, 
  toothed 
  mandibles, 
  the 
  well-de- 
  

   veloped 
  one- 
  or 
  two-lobed 
  maxillae 
  with 
  their 
  three-jointed 
  palpi, 
  and 
  the 
  

   well- 
  developed 
  second 
  maxillae 
  (labium), 
  also 
  the 
  four-jointed 
  antennae, 
  

   and 
  the 
  presence 
  of 
  ocelli, 
  while 
  showing 
  that 
  the 
  existing 
  carnivorous 
  

   larvae 
  are 
  the 
  most 
  specialized 
  and 
  highly 
  developed, 
  also 
  show 
  that 
  

   they 
  have 
  undergone 
  the 
  least 
  modification 
  from 
  the 
  primitive 
  type 
  of 
  

   Coleopterous 
  larva. 
  In 
  the 
  scavenger 
  larval 
  forms, 
  as 
  the 
  Silphidae, 
  Der- 
  

   mestidae 
  and 
  allied 
  families, 
  the 
  mouth-parts 
  begin 
  to 
  be 
  modified 
  and 
  

   less 
  developed, 
  and 
  the 
  form 
  of 
  the 
  body 
  undergoes 
  a 
  change, 
  becoming 
  

   thicker 
  and 
  with 
  less 
  developed 
  feet. 
  

  

  In 
  the 
  Elateridae 
  and 
  Scarabaeidae, 
  which 
  in 
  general 
  are 
  phytopha- 
  

   gous, 
  we 
  see 
  a 
  still 
  more 
  decided 
  change 
  j 
  the 
  body 
  becoming 
  cylindrical 
  

   and 
  the 
  mouth-parts 
  more 
  aberrant. 
  

  

  In 
  the 
  wood-boring 
  Buprestidae 
  and 
  Cerambycidae, 
  and 
  in 
  the 
  leaf- 
  

   eating 
  Chrysomelid 
  larvae, 
  we 
  witness 
  a 
  decided 
  departure 
  from 
  the 
  

   carnivorous 
  type; 
  the 
  mouth-parts 
  show 
  a 
  tendency 
  to 
  become 
  more 
  or 
  

   less 
  aborted, 
  the 
  legs 
  are 
  frequently 
  wanting 
  and 
  the 
  body 
  more 
  or 
  less 
  

   maggot-like. 
  Finally, 
  the 
  tendency 
  to 
  a 
  gradual, 
  degradation 
  and 
  atrophy 
  

   of 
  the 
  head, 
  mouth 
  -parts 
  and 
  legs 
  culminates 
  in 
  the 
  grubs 
  of 
  the 
  weevils 
  

   (Curculionidae 
  and 
  Scolytidae), 
  placing 
  them 
  at 
  the 
  foot 
  of 
  the 
  Cole- 
  

   opterous 
  series, 
  and 
  shows 
  that 
  they 
  have 
  undergone 
  the 
  greatest 
  modi- 
  

   fication 
  of 
  form, 
  and 
  have 
  become 
  adapted 
  to 
  conditions 
  the 
  most 
  unlike 
  

   those 
  which 
  constituted 
  the 
  environment 
  of 
  the 
  primitive 
  Coleopterous 
  

   larva. 
  

  

  The 
  relative 
  form 
  of 
  the 
  maxillae 
  appears 
  to 
  be 
  a 
  good 
  index 
  as 
  to 
  the 
  

   general 
  development 
  of 
  the 
  body 
  in 
  the 
  different 
  groups 
  of 
  Coleoptera, 
  

   especially 
  those 
  standing 
  above 
  the 
  wood-boring 
  families. 
  The 
  facts 
  

   may, 
  for 
  convenience, 
  be 
  arranged 
  in 
  the 
  following 
  form: 
  

  

  Cicindelidce. 
  — 
  Maxilla 
  with 
  a 
  maxillary 
  lobe 
  qr 
  mala 
  proper 
  ending 
  in 
  

   a 
  2-jointed 
  appendage 
  which 
  is 
  longer 
  than 
  the 
  3-jointed 
  palpus. 
  (An- 
  

   tennae 
  4 
  jointed 
  ; 
  3 
  ocelli.) 
  

  

  Oara&ifZce.— 
  Maxilla 
  with 
  the 
  mala 
  2-jointed; 
  maxillary 
  palpus 
  4- 
  

   jointed. 
  (Antennae 
  4-jointed, 
  bifurcate; 
  ocelli 
  often 
  present.) 
  

  

  Dytiscidce 
  (and 
  Hydradephaga 
  in 
  general). 
  — 
  Maxilla 
  with 
  the 
  mala 
  

   absent; 
  the 
  palpi 
  4-jointed. 
  

  

  The 
  maxilla 
  in 
  the 
  aquatic 
  forms 
  of 
  the 
  Carabid 
  type 
  is 
  only 
  a 
  modi- 
  

   fication 
  of 
  the 
  Geodephagous 
  maxilla; 
  the 
  terminal 
  palpal 
  joint 
  being 
  

   acute 
  and 
  raptorial. 
  

  

  