318  Annual  Report  for  1910  of  the  Zoologist. 
camphor,  which  give  off  vapours  which  penetrate  to  the  breathing 
organs.  The  latter  treatment  is  seldom  more  than  partially 
effective,  and  direct  fumigation  in  a closed  room  is  more  likely 
to  kill  the  worms.  It  is,  however,  very  drastic  and  severe,  and 
it  is  doubtful  whether  it  is  worth  resorting  to  except  in  the  case 
of  valuable  animals. 
If  a pig  is  seen  to  be  affected  by  this  disease  it  should  be 
killed  at  once.  If  not,  it  should  at  least  be  isolated,  and  the 
sty  disinfected. 
Corn  Crop  Pests. 
Judging  from  the  number  of  specimens  received,  frit-fly  in 
oats  was  nothing  like  so  prevalent  as  in  the  previous  season. 
A certain  number  of  cases  of  all  the  ordinary  corn-crop  pests 
were  reported,  but  the  one  most  often  complained  of  was 
the  wheat  bulb-fly,  which  annually  takes  a considerable  toll 
from  the  wheat  crop,  and  against  which  no  effective  measures 
are  known. 
A practical  agriculturist  of  wide  experience  recently  told 
me  that  he  had  observed  a rather  curious  fact,  and  it  would  be 
interesting  to  know  whether  others  have  had  a like  experience. 
He  finds  that  he  never  has  wheat  bulb-fly  if  the  land  on  which  the 
wheat  is  was  fully  covered  by  a crop  throughout  the  preceding 
August.  He  gives  a very  striking  case  in  point.  After  a crop 
of  potatoes  of  a variety  which  made  comparatively  little  leafage 
and  left  broad  bare  spaces  between  the  rows,  the  succeeding 
wheat  crop  was  only  affected  by  wheat  bulb-fly  in  the  rows 
which  tallied  exactly  with  the  bare  spaces  of  the  previous  year, 
the  rest  of  the  wheat  being  quite  free.  I have  obtained  no  corro- 
boration of  this  view  from  others,  but  it  seems  difficult  to 
explain  as  an  accident,  and  if  it  were  generally  true  it  would 
have  a practical  application  to  wheat-growing  where  the  fly  is 
prevalent.  It  seems  useless  to  try  to  account  for  what  after 
all  may  not  be  the  general  experience,  but  if  true,  the  explana- 
tion would  probably  be  found  in  the  grasses  which  spring  up 
on  the  uncovered  land  and  attract  the  fly  to  lay  its  eggs  among 
them. 
In  the  case  of  corn  pests  it  is  seldom  possible  to  do  anything 
while  the  attack  is  on,  and  the  destruction  of  the  insects  in  the 
stubble  and  in  the  cavings  after  threshing  does  not  suffice  to 
prevent,  though  it  may  mitigate,  a future  attack.  It  is  there- 
fore important  to  note  any  conditions  of  culture  which  seem 
to  discourage  the  particular  insect  in  question,  for  there  is  no 
method  of  treatment  so  hopeful  as  a suitable  rotation  of  crops. 
Root  and  Garden  Crop  Pests. 
Advice  was  given  with  regard  to  a variety  of  pests  in  this 
section,  but  they  were  mostly  well  known  insects  and  call  for 
