﻿PROCEEDINGS 
  OF 
  THE 
  FOURTH 
  ENTOMOLOGICAL 
  MEETING 
  245 
  

  

  become 
  frantic 
  in 
  their 
  efforts 
  to 
  escape. 
  High 
  temperatures 
  cause 
  

   sudden 
  death 
  " 
  (8). 
  Even 
  such 
  high 
  temperatures 
  as 
  are 
  within 
  the 
  

   limits 
  of 
  atmospheric 
  changes 
  are 
  known 
  to 
  effect 
  insects 
  adversely, 
  

   and 
  it 
  is 
  on 
  record 
  that 
  in 
  France 
  in 
  1911 
  a 
  single 
  day 
  of 
  excessive 
  heat 
  

   was 
  enough 
  to 
  kill 
  off 
  all 
  the 
  rose 
  aphids 
  (2). 
  

  

  The 
  methods 
  of 
  killing 
  insects 
  by 
  subjecting 
  them 
  to 
  higher 
  tempera- 
  

   tures 
  is 
  not 
  new 
  to 
  us. 
  It 
  has 
  been 
  practised 
  in 
  India 
  from 
  very 
  remote 
  

   times. 
  " 
  Spreading 
  wheat 
  in 
  the 
  sun 
  and 
  stirring 
  it 
  occasionally 
  is 
  

   said 
  to 
  make 
  the 
  weevils 
  leave 
  it." 
  (3, 
  16). 
  And 
  this 
  practice 
  is 
  common 
  

   even 
  to-day. 
  Infested 
  grain 
  if 
  it 
  is 
  spread 
  in 
  the 
  sun 
  at 
  115° 
  or 
  116° 
  

   F 
  for 
  two 
  hours 
  kills 
  off 
  most 
  weevils 
  (20). 
  

  

  Artificial 
  heat 
  is 
  coming 
  into 
  use 
  for 
  the 
  purpose 
  of 
  dealing 
  with 
  the 
  

   insects 
  of 
  the 
  stored 
  products, 
  and 
  superheating 
  in 
  mills 
  and 
  godowns 
  

   has 
  come 
  into 
  general 
  practice 
  in 
  some 
  countries 
  (7, 
  8, 
  11, 
  17, 
  19). 
  As 
  

   to 
  the 
  temperature 
  which 
  is 
  fatal 
  to 
  these 
  insects 
  there 
  is 
  very 
  great 
  

   divergence 
  of 
  opinion. 
  Some 
  investigators 
  put 
  it 
  at 
  as 
  low 
  a 
  figure 
  

   as 
  110° 
  F., 
  while 
  others 
  put 
  it 
  at 
  as' 
  high 
  a 
  point 
  as 
  145° 
  F. 
  Thompsoi^ 
  

   says 
  that 
  weevils 
  cannot 
  stand 
  a 
  temperature 
  of 
  119° 
  F. 
  for 
  more 
  tha: 
  

   2 
  to 
  3 
  minutes 
  (20). 
  Schribaux 
  maintains 
  that 
  weevils 
  are 
  killed 
  in 
  

   2 
  minutes 
  at 
  122° 
  F. 
  (18). 
  Lefroy, 
  at 
  a 
  lecture 
  delivered 
  at 
  the 
  Eoyal 
  

   Institution, 
  on 
  the 
  destruction 
  of 
  grain 
  insects 
  by 
  heat, 
  said 
  that 
  a 
  

   temperature 
  of 
  145° 
  F. 
  applied 
  for 
  3 
  minutes 
  killed 
  every 
  insect 
  pest 
  of 
  

   the 
  grain. 
  This 
  variation 
  is 
  probably 
  due 
  to 
  the 
  varying 
  conditions 
  

   under 
  which 
  the 
  different 
  investigators 
  have 
  worked. 
  It 
  seems 
  likely 
  that 
  

   insects 
  of 
  the 
  tropics 
  get 
  used 
  to 
  higher 
  temperatures 
  and 
  can 
  stand 
  

   excessive 
  heat 
  much 
  better 
  than 
  their 
  fellow-beings 
  of 
  the 
  cooler 
  regions. 
  

   It 
  has 
  been 
  stated 
  that 
  110° 
  F. 
  maintained 
  long 
  enough 
  to 
  penetrate 
  

   the 
  tissues 
  of 
  the 
  body 
  kills 
  insect 
  pests 
  of 
  grain, 
  but 
  in 
  the 
  elevator 
  

   at 
  Lyallpur 
  the 
  temperatures 
  in 
  the 
  bins 
  went 
  as 
  high 
  as 
  113° 
  F. 
  during 
  

   summer 
  and 
  still 
  the 
  insects 
  were 
  breeding 
  quite 
  well. 
  

  

  In 
  view 
  of 
  the 
  above 
  considerations, 
  experiments 
  were 
  started 
  on 
  

   the 
  larvae 
  of 
  Trogoderma 
  khapra, 
  the 
  commonest 
  pest 
  of 
  wheat 
  in 
  the 
  

   Punjab, 
  in 
  order 
  to 
  discover 
  the 
  lethal 
  temperatures 
  of 
  the 
  stored 
  grain 
  

   pests. 
  This 
  insect 
  was 
  selected 
  for 
  our 
  experiments, 
  because 
  its 
  larvae 
  

   are 
  known 
  to 
  be 
  the 
  most 
  resistant 
  of 
  all 
  the 
  stages 
  of 
  its 
  life-history 
  

   to 
  the 
  severities 
  of 
  temperature 
  and 
  can 
  live 
  for 
  a 
  long 
  time 
  without 
  

   food. 
  

  

  The 
  following 
  simple 
  apparatus 
  was 
  used 
  in 
  our 
  experiments. 
  

  

  A 
  large 
  flask 
  of 
  2,400 
  C. 
  C. 
  capacity 
  was 
  used 
  to 
  get 
  an 
  atmosphere 
  

  

  of 
  the 
  desired 
  temperature. 
  This 
  was 
  heated 
  on 
  a 
  water-bath 
  (Plate 
  

  

  XLI, 
  fig. 
  1). 
  The 
  flask 
  was 
  fitted 
  with 
  a 
  cork 
  with 
  two 
  holes, 
  through 
  

  

  one 
  of 
  these 
  a 
  thermometer 
  was 
  introduced 
  and 
  through 
  the 
  other 
  hole, 
  

  

  