280  Ainiiial  Report  for  1004  of  the  Zoologist. 
remedies  for  the  actual  attack,  if  adopted  in  time,  often  result 
ill  the  saving  of  at  least  a considerable  portion  of  the  crop. 
With  perennial  plants  like  currant  hushes  or  fruit  trees, 
there  is  no  dilficulty  in  understanding  hovv’  the  pest  is  able 
to  maintain  itself  year  after  year  ; hut  the  case  is  different 
with  regard  to  annuals.  What  becomes  of  the  insect  when 
the  crop — hops  or  corn  or  roots — has  been  removed?  It  is 
only  in  a few  instances  that  we  know  with  any  certainty, 
and  in  these  they  either  continue  to  live  on  weeds  more  or 
less  closely  allied  to  their  food  plant,  or  they  migrate  to  an 
entirely  different  plant — as  the  hop  aphis  migrates  to  the 
sloe — and  assume  an  appearance  so  different  that  onh’  careful 
research  has  been  able  to  prove  tlie  identity  of  the  insect 
under  two  distinct  forms.  In  a great  many  cases  we  have 
no  knowledge  as  to  where  the  jiest  spends  the  months  when 
its  usual  food  plant  is  not  in  evidence, 
and  can  only  presume  that  it  has  the 
power  of  hibernating  in  the  ground  and 
remaining  dormant  till  the  croi^  is  again 
ready  for  it. 
Blight  insects  may  attack  any  part 
of  a plant.  Some  feed  at  the  root,  like 
the  root  form  of  Phylloxera  vaslatrix, 
the  vine  ai)his.  Others  establish  them- 
selves on  the  rough  bark  of  the  trunk 
and  branches  of  trees,  like  the  “American 
blight,”  but  nearly  all  those  which  con- 
cern the  agriculturist  feed  on  the  succu- 
lent young  shoots  or  on  the  leaves,  and 
in  the  latter  case  are  almost  always  to  be  found  on  the  under 
side  of  the  leaf.  This  makes  their  effective  treatment  by  washes 
rather  diflicult,  and  care  must  always  be  taken  to  direct  the 
spray  as  far  as  possible  so  as  to  strike  the  leaves  fi’om  below. 
There  are  numerous  aphis  washes  in  the  market,  and  many 
of  them  are  excellent.  For  those,  however,  who  iDrefer  to 
manufacture  their  own,  recipes  are  here  given  for  two  washes 
which  are  easily  made  and  generally  effective. 
A. — Make  a “stock  emulsion”  by  dissolving  half  a pound 
of  soft  soap  in  one  gallon  of  soft  water,  adding 
two  gallons  of  paraffin  (kerosene)  oil,  and  stirring 
thoroughlj".  This  stock  emulsion  must  be  diluted 
for  use,  fifteen  gallons  of  soft  water  being  added  to 
the  three  gallons  of  emulsion.  Paraffin  or  kerosene 
oil  is  a substance  of  somewhat  uncertain  strength  as 
supplied  commercially,  and  it  is  as  well  to  make  a 
trial  of  the  wash,  and  to  dilute  it  further  if  it  seems 
injurious  to  the  foliage. 
