﻿218 
  REPOKT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  liairy 
  than 
  in 
  the 
  male, 
  while 
  the 
  10th 
  (terminal) 
  joint 
  is 
  acute 
  at 
  tip, 
  

   -and 
  subdivided 
  into 
  four 
  subjoints. 
  The 
  abdomen 
  is 
  as 
  long 
  and 
  as 
  

   wide 
  as 
  the 
  thorax, 
  endiug 
  in 
  a 
  long, 
  sharp 
  point, 
  the 
  short 
  but 
  distinct 
  

   ovii)ositor 
  extending 
  slightly 
  beyond 
  the 
  tip 
  of 
  the 
  body. 
  There 
  is 
  a 
  

   slightly 
  marked 
  pale 
  spot 
  above 
  on 
  the 
  second 
  segment. 
  Length 
  2.4-3 
  

   millimeters 
  (0.10-0.12 
  inch). 
  

  

  This 
  parasite 
  was 
  first 
  described 
  by 
  Say, 
  his 
  specimens 
  occurring 
  at 
  or 
  

   near 
  Philadelphia 
  ; 
  it 
  was 
  observed 
  by 
  Herrick 
  in 
  1833, 
  in 
  Connecticut, 
  

   and 
  in 
  1877 
  we 
  bred 
  it 
  from 
  iniparia 
  of 
  the 
  Hessian 
  Fly 
  received 
  from 
  

   Ohio 
  5 
  and, 
  as 
  stated 
  by 
  Professor 
  Cook, 
  it 
  is 
  sufficiently 
  abundant 
  in 
  

   Michigan 
  to 
  destroy 
  the 
  Hessian 
  Fly 
  in 
  great 
  numbers, 
  and 
  is 
  prob- 
  

   ably 
  distributed 
  throughout 
  the 
  Hessian 
  Fly 
  area. 
  

  

  So 
  destructive 
  are 
  this 
  and 
  other 
  i^arasites 
  to 
  the 
  Hessian 
  Fly 
  that 
  as 
  

   early 
  as 
  1841 
  Herrick 
  claimed 
  that 
  in 
  Connecticut 
  "a 
  very 
  large 
  propor- 
  

   tion, 
  probably 
  more 
  than 
  nine-tenths, 
  of 
  every 
  generation 
  of 
  the 
  Hessian 
  

   Fly 
  is 
  destroyed 
  by 
  parasites." 
  This 
  work 
  is 
  mainly, 
  we 
  doubt 
  not, 
  done 
  

   by 
  the 
  chalcid 
  parasite 
  under 
  consideration. 
  It 
  is 
  to 
  this 
  insect 
  more 
  

   than 
  to 
  any 
  other 
  means 
  in 
  nature 
  that 
  we 
  owe 
  the 
  general 
  immunity 
  in 
  

   certain 
  years 
  from 
  the 
  attacks 
  of 
  the 
  Hessian 
  Fly 
  in 
  most 
  wheat 
  regions, 
  

   and 
  to 
  this 
  cause 
  that 
  during 
  certain 
  years 
  the 
  fly 
  is 
  kept 
  wholly 
  within 
  

   bounds. 
  Few 
  people, 
  even 
  naturalists, 
  have 
  any 
  adequate 
  idea 
  of 
  the 
  

   good 
  done 
  by 
  these 
  minute 
  i)arasites. 
  AVhat 
  was 
  the 
  fact 
  in 
  Connecticut 
  

   in 
  1841, 
  and 
  the 
  few 
  years 
  precediug, 
  has 
  been 
  the 
  case 
  in 
  Michigan, 
  

   according 
  to 
  Mr. 
  F. 
  S. 
  Sleeper, 
  of 
  Galesburg, 
  Mich., 
  who 
  writes 
  us 
  that 
  

   the 
  Hessian 
  Fly 
  was 
  nearly 
  exterminated 
  in 
  Kalamazoo 
  County 
  by 
  

   SemioteUus 
  destructor^ 
  nearly 
  all 
  the 
  "flaxseeds" 
  in 
  the 
  crop 
  of 
  1877 
  

   having 
  been 
  destroyed 
  by 
  this 
  friendly 
  parasite. 
  He 
  writes 
  us 
  that 
  in 
  

   the 
  autumn 
  of 
  1877 
  he 
  found 
  these 
  parasites 
  in 
  the 
  wheat-fields 
  in 
  count- 
  

   less 
  numbers, 
  and 
  that 
  the 
  perfect 
  Hessian 
  Fly 
  was 
  difficult 
  to 
  find. 
  

  

  No 
  one 
  since 
  'Herrick 
  recorded 
  his 
  observations 
  has 
  made 
  very 
  care- 
  

   ful 
  observations 
  on 
  the 
  habits 
  of 
  these 
  iiarasites. 
  He 
  states 
  that 
  : 
  

  

  Ic 
  pierces 
  the 
  slieatli 
  of 
  tlie 
  stalk 
  (making 
  a 
  liole 
  too 
  small 
  to 
  "be 
  detected 
  by 
  a 
  pow- 
  

   erful 
  microscope), 
  and 
  deposits 
  an 
  egg 
  in 
  the 
  pupa 
  within. 
  This 
  is 
  done 
  chiefly 
  in 
  

   June. 
  The 
  perfect 
  insect 
  is 
  evolved 
  in 
  the 
  summer 
  and 
  autumn 
  succeeding, 
  eating- 
  

   its 
  way 
  through 
  tlie 
  x)uparium 
  and 
  the 
  sheath 
  of 
  the 
  leaf. 
  

  

  Herrick 
  also 
  states 
  that 
  a 
  second 
  parasite, 
  very 
  similar 
  to 
  the 
  Semio- 
  

   teUus 
  destructor^ 
  " 
  but 
  with 
  mere 
  rudinients 
  of 
  wings, 
  is 
  sometimes 
  evolved 
  

   from 
  the 
  pupne 
  of 
  the 
  Hessian 
  Fly. 
  I 
  am 
  in^oubt 
  whether 
  it 
  should 
  be 
  

   •considered 
  a 
  distinct 
  species 
  or 
  only 
  a 
  variety." 
  

  

  A 
  third 
  parasite 
  was 
  reared 
  by 
  Herrick 
  in 
  Connecticut. 
  It 
  is 
  an 
  in- 
  

   sect 
  of 
  the 
  tribe 
  Chalcidiw, 
  whose 
  genus 
  he 
  did 
  not 
  determine. 
  Its 
  habits 
  

   were 
  like 
  those 
  of 
  SemioteUus, 
  and 
  wingless 
  females 
  of 
  this 
  species 
  were 
  

   also 
  found. 
  

  

  A 
  fourth 
  parasite, 
  noticed 
  by 
  Herrick, 
  belongs 
  to 
  Latreille's 
  tribe 
  

   Oxyurij 
  but 
  the 
  genus 
  was 
  not 
  determined. 
  In 
  habits 
  it 
  agreed 
  with 
  

  

  