244 
Insect  Powder. 
Am.  Jour.  Pharnn 
May,  1879. 
is  singular  that  while  there  are  many  other  composite  plants  closely- 
related  to  the  genus  Pyrethrum,  as  yet  this  peculiar  property  has  been 
found  only  in  plants  belonging  to  this  genus,  and  even  within  this  limit 
there  are  several  species  whose  value  as  insecticides  is  very  slight.  A 
large  number  of  Composite  indigenous  to  Austria  have  been  tested  and 
found  to  be  of  no  value  in  this  respect.  The  flowers  of  Tansy 
{Tanacetum  vulgare)  are  said  to  have  a  slight  stupefying  effect. 
The  Pyrethrums  are  hardy  plants  which  bloom  abundantly  the  second 
year  from  seed.  The  powder  is  prepared  from  the  half-opened  flowers 
gathered  during  dry  weather  and  dried  in  the  shade  under  cover,  but 
the  process  of  gathering,  drying  and  preparing  involves  so  much  time 
that  their  culture  can  only  be  made  profitable  where  labor  is  cheap. 
Insect  powders  have  not  attracted  general  attention  as  insecticides- 
until  within  the  last  three  or  four  years,  during  which  time  they  have 
been  introduced  in  various  forms  in  packages  and  boxes,  accompanied 
by  suitable  blowers  or  insect  guns  for  the  purpose  of  properly  distrib- 
uting the  powder,  and  recommended  for  the  destruction  of  flies,  cock- 
roaches, fleas,  bugs,  etc.  Sometimes  these  prepared  articles  have  been 
artificially  colored  so  as  to  disguise  their  source,  but  all  have  owed  their 
activity  solely  to  the  presence  of  the  powdered  flowers  of  one  or  other  of 
these  Pyrethrums. 
House  flies  are  very  sensitive  to  the  effects  of  these  powders.  A  few 
puffs  of  the  dust  from  an  insect  gun,  blown  into  the  air  of  a  room  with 
the  doors  closed,  the  discharges  directed  towards  those  parts  where  flies 
are  congregated,  will  stupefy  and  kill  them  within  a  very  short  time. 
The  powder  is  somewhat  pungent,  and  to  breathe  an  atmosphere 
charged  with  it  will  frequently  cause  a  slight  sneezing,  but  beyond  this 
the  operator  need  not  anticipate  any  annoyance.  Frequently  during  the 
past  summer,  when  flies  have  been  troublesome,  we  have  pretty  thor- 
oughly charged  the  air  in  our  dining-room  and  kitchen  at  night,  closing 
the  doors,  and  in  the  morning  found  all,  or  nearly  all,  the  flies  lying 
dead  on  the  floors.  A  few  minutes  after  its  use  they  begin  to  drop  on 
their  backs,  and  after  a  very  short  time  die  ;  if  a  room  be  closed  for 
half  an  hour  after  using  the  powder,  few,  if  any,  will  escape.  By  some 
this  energetic  action  has  been  attributed  to  the  presence  of  a  volatile  oil 
in  the  flowers,  by  other  and  later  investigators  to  a  peculiar  crystalline 
principle  believed  to  be  an  alkaloid,  but  this  point  does  not  as  yet  seem- 
to  be  fully  settled. 
