﻿368 
  

  

  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  their 
  existence 
  from 
  a 
  study 
  of 
  the 
  changes 
  in 
  the 
  shape 
  of 
  the 
  

  

  larval 
  mandibles. 
  

  

  After 
  a 
  week 
  of 
  feasting 
  on 
  honey-flavored 
  meat 
  the 
  larva 
  has 
  

  

  leached 
  its 
  full 
  growth. 
  Nothing 
  savory 
  remains 
  to 
  be 
  eaten. 
  The 
  

   cell 
  is 
  cluttered 
  with 
  the 
  unpalatable 
  legs, 
  wings, 
  

   and 
  horny 
  armor 
  of 
  the 
  bees. 
  

  

  Now 
  we 
  can 
  examine 
  the 
  larva 
  (pi. 
  2, 
  fig. 
  5) 
  

   more 
  carefully 
  and 
  correlate 
  some 
  of 
  its 
  habits 
  

   with 
  its 
  structure. 
  It 
  has 
  a 
  body 
  that 
  is 
  slender 
  

   and 
  fusiform, 
  all 
  covered 
  with 
  a 
  stubble 
  of 
  

   short, 
  brown 
  bristles. 
  The 
  head 
  is 
  very 
  small 
  

   and 
  for 
  that 
  reason 
  well 
  suited 
  to 
  pry 
  into 
  the 
  

   narrow 
  foramina 
  of 
  body 
  walls 
  to 
  reach 
  the 
  food 
  

   that 
  is 
  stored 
  away 
  in 
  stout, 
  chitinous 
  boxes. 
  

   The 
  anal 
  segment 
  of 
  the 
  larva 
  ends 
  in 
  a 
  subcylin- 
  

   drical 
  projection 
  which 
  is 
  often 
  telescoped 
  in 
  and 
  

   out 
  of 
  the 
  abdominal 
  somites. 
  This 
  tail 
  makes 
  a 
  

   hand}'' 
  lever 
  for 
  propulsion 
  when 
  the 
  grub 
  has 
  

  

  need 
  to 
  shift 
  its 
  position. 
  The 
  tail 
  is 
  withdrawn, 
  pressed 
  against 
  a 
  

  

  fulcrum, 
  and 
  extended. 
  The 
  extension 
  gives 
  a 
  propelling 
  force 
  to 
  

  

  the 
  whole 
  body, 
  and 
  the 
  grub 
  with 
  his 
  caudal 
  prolongation 
  poles 
  his 
  

  

  way 
  around 
  the 
  narrow 
  confines 
  of 
  the 
  cell. 
  

  

  Fig. 
  4. 
  — 
  Philanthus 
  

   gibbosus. 
  Head 
  of 
  

   full-grown 
  larva. 
  

   (X 
  36.) 
  

  

  Fig. 
  5. 
  — 
  Philanthus 
  gibbosus. 
  Larval 
  mandibles, 
  showing 
  progressive 
  changes 
  from 
  

   newly-hatched 
  larva 
  to 
  prepupal 
  form. 
  Drawn 
  to 
  scale. 
  ( 
  X 
  150.) 
  

  

  The 
  microscope 
  reveals 
  nothing 
  exceptional 
  about 
  the 
  larva's 
  head 
  

   (fig. 
  4). 
  The 
  lower 
  margin 
  of 
  the 
  clypeus 
  is 
  notched, 
  and 
  its 
  sides 
  

   shield 
  two 
  teeth 
  of 
  the 
  tridentate 
  mandibles 
  — 
  these 
  may 
  be 
  charac- 
  

   ters 
  of 
  interest 
  to 
  the 
  taxonomist. 
  

  

  A 
  study 
  was 
  made 
  of 
  the 
  mandibles 
  from 
  the 
  newly 
  hatched 
  larva 
  

   to 
  the 
  adult, 
  and 
  it 
  showed 
  an 
  interesting 
  mutation 
  in 
  these 
  organs. 
  

  

  