﻿267 
  

  

  ON 
  THE 
  OCCURRENCE 
  OF 
  LEAF-EATING 
  SAWFLIES 
  ON 
  CEREALS 
  

  

  IN 
  BRITAIN. 
  

  

  By 
  A. 
  Roebuck, 
  

  

  Lecturer 
  in 
  Agricultural 
  Biology 
  and 
  Adviser 
  in 
  Agricultural 
  Entomology, 
  

   Harper 
  Adams 
  Agricultural 
  College. 
  

  

  Each 
  season 
  since 
  1918 
  numbers 
  of 
  leaf-feeding 
  sawfly 
  larvae 
  have 
  been 
  taken 
  

   during 
  the 
  months 
  of 
  June 
  and 
  July 
  in 
  both 
  oat 
  and 
  wheat 
  crops. 
  The 
  larvae 
  feed 
  

   along 
  the 
  edges 
  of 
  the 
  blades 
  during 
  the 
  day 
  and 
  usually 
  cut 
  off 
  the 
  upper 
  portion 
  

   (fig- 
  1). 
  

  

  *■ 
  

  

  Fig. 
  1. 
  Wheat 
  leaves 
  damaged 
  by 
  larvae 
  of 
  Dolerus 
  and 
  Pachynematus. 
  

  

  Attempts 
  to 
  breed 
  the 
  adults 
  from 
  these 
  succeeded 
  in 
  1920 
  and 
  1921, 
  two 
  species 
  

   having 
  been 
  found 
  to 
  be 
  responsible 
  for 
  the 
  damage, 
  Pachynematus 
  clitellus, 
  Lep., 
  

   and 
  Dolerus 
  haematodis, 
  Klug, 
  which 
  were 
  very 
  kindly 
  identified 
  by 
  the 
  Rev. 
  F. 
  D. 
  

   Morice. 
  The 
  larvae 
  disappear 
  from 
  the 
  fields 
  during 
  the 
  latter 
  half 
  of 
  July 
  and 
  pupate 
  

   in 
  the 
  ground. 
  Emergence 
  of 
  the 
  sawflies 
  takes 
  place 
  in 
  the 
  laboratory 
  during 
  the 
  

   first 
  half 
  of 
  May. 
  From 
  measurements 
  of 
  larvae 
  indoors 
  and 
  in 
  the 
  field 
  this 
  closely 
  

   corresponds 
  with 
  the 
  time 
  of 
  emergence 
  out 
  of 
  doors. 
  

  

  Species 
  of 
  both 
  Dolerus 
  and 
  Pachynematus 
  have 
  been 
  recorded 
  in 
  America 
  as 
  

   attacking 
  cereals 
  (1, 
  2). 
  

  

  