﻿TRANSFORMATIONS 
  OF 
  THE 
  HESSIAN 
  FLY. 
  209 
  

  

  This 
  brown 
  case 
  protects 
  the 
  growing 
  pupa 
  within 
  the 
  skin 
  of 
  the 
  latter, 
  

   finally 
  separating 
  from 
  the 
  cast 
  larval 
  skin, 
  called 
  the 
  ptipa-case 
  or 
  

   puparmm^ 
  and 
  which 
  serves 
  as 
  a 
  sort 
  of 
  cocoon 
  to 
  protect 
  the 
  pale, 
  soft- 
  

   bodied 
  pupa 
  within. 
  While 
  many 
  two-winged 
  gall-flies 
  are 
  protected 
  by 
  

   the 
  galls 
  within 
  which 
  they 
  live, 
  others, 
  like 
  the 
  larval 
  wheat 
  and 
  clover- 
  

   seed 
  midge 
  and 
  the 
  pitch-pine 
  midge, 
  spin 
  true 
  cocoons 
  of 
  silk; 
  and 
  the 
  

   Hessian 
  Fly 
  is 
  the 
  only 
  species 
  of 
  the 
  genus 
  or 
  family, 
  so 
  far 
  as 
  we 
  know, 
  

   which 
  assumes 
  this 
  iiuparium 
  state, 
  which 
  is 
  characteristic 
  of 
  the 
  house 
  

   fly 
  and 
  other 
  species 
  of 
  Muscidse 
  and 
  allied 
  families, 
  in 
  which 
  the 
  pupa 
  

   is 
  said 
  to 
  be 
  coarctate, 
  i. 
  e., 
  protected 
  by 
  the 
  cast 
  dried 
  brown 
  skin 
  of 
  

   tlie 
  maggot 
  or 
  larva. 
  

  

  From 
  the 
  decided 
  resemblance 
  to 
  a 
  flaxseed 
  the 
  insect, 
  when 
  at 
  this 
  

   stage 
  of 
  its 
  transformations, 
  is 
  said 
  to 
  be 
  in 
  the 
  " 
  flaxseed" 
  state. 
  It 
  is, 
  

   however, 
  rather 
  flatter 
  than 
  a 
  flaxseed, 
  being 
  pinched, 
  as 
  it 
  were, 
  at 
  the 
  

   head-end 
  of 
  the 
  body. 
  I 
  have 
  taken 
  the 
  semi-pupa 
  or 
  incomifletely- 
  

   formed 
  pupa 
  from 
  the 
  flaxseed 
  December 
  1. 
  In 
  this 
  flaxseed 
  state 
  the 
  

   partly-formed 
  pupa 
  resides 
  during 
  the 
  five 
  winter 
  months 
  of 
  the 
  year. 
  

  

  In 
  early 
  spring, 
  during 
  warm 
  weather 
  in 
  April, 
  the 
  semi-pupa 
  rapidly 
  

   transforms 
  into 
  the 
  complete 
  pupal 
  or 
  chrysalis 
  state. 
  

  

  Thepupa 
  (Plate 
  Y, 
  C). 
  — 
  As 
  we 
  have 
  not 
  personally 
  observed 
  the 
  mode 
  

   in 
  which 
  the 
  fly 
  issues 
  from 
  the 
  pupa 
  and 
  its 
  case, 
  we 
  extract 
  the 
  follow- 
  

   ing 
  account 
  from 
  Fitch. 
  By 
  the 
  time 
  the 
  insect 
  reaches 
  the 
  pupa 
  state 
  

   the 
  flaxseed 
  case 
  has 
  become 
  quite 
  brittle, 
  breaking 
  asunder 
  trans- 
  

   versely 
  if 
  rudely 
  handled, 
  one 
  of 
  its 
  ends 
  slipping 
  off 
  from 
  the 
  insect 
  

   within, 
  like 
  a 
  thimble 
  from 
  the 
  end 
  of 
  the 
  finger. 
  

  

  The 
  time 
  for 
  its 
  lasttransformationhaviDg 
  arrived, 
  the 
  pupa, 
  by 
  writhing 
  andbend- 
  

   iDg 
  its 
  body, 
  breaks 
  open 
  its 
  i)upariiim 
  or 
  flaxseed 
  case, 
  crawls 
  from 
  it, 
  and 
  works 
  its 
  

   w^ay 
  upward 
  within 
  the 
  sheath 
  of 
  the 
  leaf 
  until 
  it 
  comes 
  to 
  some 
  cleft 
  in 
  the 
  now 
  

   dead, 
  brittle, 
  and 
  elastic 
  straw. 
  Through 
  this 
  cleft 
  it 
  crowds 
  its 
  body 
  until 
  all 
  exce^it 
  

   the 
  tip 
  of 
  the 
  abdomen 
  is 
  protruded 
  into 
  the 
  air, 
  the 
  elasticity 
  of 
  the 
  straw 
  causing 
  

   it 
  to 
  close 
  together 
  upon 
  the 
  tip 
  of 
  the 
  abdomen 
  sufficiently 
  to 
  hold 
  the 
  pupa 
  in 
  this 
  

   situation 
  secure 
  from 
  falling 
  to 
  the 
  ground; 
  and, 
  as 
  if 
  to 
  preserve 
  the 
  body 
  in 
  a 
  hor- 
  

   izontal 
  position, 
  the 
  feet 
  are 
  slightly 
  separated 
  from 
  the 
  abdomen 
  and 
  directed 
  obliquely 
  

   d-ownwards, 
  with 
  their 
  tips 
  pressed 
  against 
  the 
  side 
  of 
  the 
  straw, 
  thus 
  curiously 
  serv- 
  

   ing, 
  like 
  the 
  brace 
  to 
  a 
  beam 
  or 
  to 
  the 
  arm 
  of 
  a 
  signpost, 
  to 
  support 
  the 
  body 
  from 
  

   inclining 
  downwards. 
  Thus 
  securely 
  fixed 
  and 
  now 
  freely 
  exposed 
  to 
  the 
  drying 
  in- 
  

   fluence 
  of 
  the 
  atmosphere, 
  the 
  outer 
  membrane 
  of 
  the 
  pupa 
  exhales 
  its 
  moisture, 
  and, 
  

   as 
  it 
  becomes 
  dried, 
  cracks 
  apart 
  upon 
  the 
  back 
  or 
  upper 
  side 
  of 
  the 
  thorax. 
  Out 
  of 
  

   this 
  opening 
  the 
  inclosed 
  fly 
  protrudes 
  its 
  head 
  and 
  thorax,"more 
  and 
  more, 
  as 
  it 
  grad- 
  

   ually 
  withdraws 
  its 
  several 
  members 
  — 
  the 
  antennse, 
  wings 
  and 
  legs 
  — 
  from 
  the 
  sheaths 
  

   in 
  which 
  they 
  are 
  respectively 
  enveloped— 
  a 
  process 
  analogous 
  to 
  that 
  of 
  withdrawing 
  

   the 
  hand 
  and 
  its 
  several 
  fingers 
  from 
  a 
  tight 
  glove 
  — 
  until 
  at 
  length, 
  entirely 
  freed 
  

   from 
  its 
  pupa-skin, 
  the 
  fly, 
  now 
  perfect 
  in 
  all 
  its 
  parts, 
  usually 
  walks 
  a 
  few 
  steps 
  

   farther 
  up 
  the 
  straw, 
  where 
  it 
  pauses 
  for 
  its 
  body 
  and 
  members 
  to 
  acquire 
  more 
  firm- 
  

   ness 
  and 
  strength 
  by 
  the 
  further 
  evaporation 
  of 
  their 
  moisture, 
  after 
  which 
  it 
  is 
  ready 
  

   to 
  spread 
  its 
  wings 
  and 
  mount 
  into 
  the 
  air. 
  

  

  The 
  Hessian 
  Fly 
  is 
  easily 
  distinguishable 
  in 
  all 
  its 
  stages 
  from 
  the 
  

   wheat 
  midge, 
  which 
  belongs 
  to 
  a 
  diflerent 
  genus, 
  Diplosis 
  (B, 
  tritici 
  of 
  

   Kirby). 
  The 
  wheat 
  midge 
  is 
  orange-colored, 
  has 
  a 
  stouter 
  body, 
  with 
  

   14 
  E 
  

  

  