VESICATING  PRINCIPLE  OP  LYTTA  VITTATA.  157 
ON  THE  SEAT  OF  THE  VESICATING  PRINCIPLE  OP  LYTTA 
VITTATA. 
By  Joseph  Leidy,  M.  D. 
Prof,  of  Anat.  in  the  University  of  Penn'a. 
It  often  occurred  to  me  that  the  vesicating  principle  of  the 
blistering  fly,  Cantharis,  Lytta,  etc.,  was  the  product  of  some 
special  organ  in  the  insect,  and  was  not  diffused  through  the 
body  of  the  animal.  In  polyps,  bees,  wasps,  mosquitos,  etc., 
we  find  the  irritating  agencies  or  poisons  produced  by  particu- 
lar cells  and  glands,  not  to  mention  the  poisons  and  odorous 
principles  found  in  special  organs  of  higher  animals.  A  few 
days  since,  observing  numerous  individuals  of  Lytta  vittata  feed- 
ing on  Amaranthus  albus,  I  collected  a  number,  and  at  a  lei- 
sure moment  experimented  with  the  different  parts  of  the  ani- 
mal to  ascertain  if  the  vesicating  principle  was  confined  to  some 
special  part  of  the  insect.  I  did  not  then  recollect  of  having 
read  of  others  who  had  performed  similar  experiments  with  the 
same  object,  but  on  examination,  find  in  Pereira,  under  the 
head  of  Cantharis  vesicatoria,  the  following  remarks: 
"  The  active  and  odorous^  principles  of  cantharides  reside 
principally  in  the  sexual  organs  of  the  animals.  Both  Farines  and 
Zier  tell  us  that  the  soft  contain  more  active  matter  than  the  hard 
parts.  It  appears,  also  that  the  posterior  is  much  more  acrid 
than  the  anterior  portion  of  the  body ;  and  Zier  says  the  ovaries 
are  particularly  rich  in  this  active  matter." 
Though  I  have  long  been  familiar  with  the  researches  of  Au- 
douin  on  the  anatomy  of  the  Spanish  fly,  I  remembered  that  he 
had  made  no  mention  of  the  source  of  irritating  power  in  the 
insect.  The  anatomy  of  Lytta  vittata  is  so  nearly  like  that  of 
the  Cantharis  vesicatoria  as  described  by  Audouin,  that  I  shall 
say  nothing  about  it  except  in  the  way  of  reference.  Without 
examining  the  work  of  Farines  and  Zier,  I  will  detail  the  results 
of  my  experiments  on  the  Lytta  vittata,  and  leave  it  to  others 
to  compare  them  with  the  experiments  of  the  former  authors. 
The  Lytta  vittata  appears  not  to  possess  the  peculiar  mice- 
like  odorous  principle  of  the  Cantharis  vesicatoria,  at  least  I 
have  not  observed  it  in  living  or  fresh  dead  specimens,  nor  in 
specimens  dried  and  long  preserved. 
When  the  Lytta  is  caught,  it  exudes  a  clear  yellow  liquid, 
