^"a^S  wSm'}   Nature  and  Structure  of  Cochineal.  359 
distribution  of  carminic  acid  in  the  animal  kingdom  is  being  denied 
it  would  seem  that  a  principle  resembling  carminic  acid  is  found 
in  the  flowers  of  horsemint,  Monarda  didyma.1Q  Reference  should 
also  be  made  to  the  monograph  on  "  Monardas  "  by  Xellie  Wake- 
man.-2 
Commercial  Varieties  of  Cochineal. 
While  the  author  of  this  article  is  hoping  for  fresh  material  with 
which  to  continue  certain  phases  of  this  investigation,  it  should  be 
said  that  there  is  very  much  that  can  be  done  by  a  study  of  the 
commercial  article.  It  is  rather  easily  prepared  for  examination 
and  with  the  use  of  stains  it  may  be  possible  to  study  the  complete 
anatomy  of  the  insect  and  distinguish  the  male  from  the  female 
larvse.  Furthermore  it  is  not  at  all  unlikely  that  different  lots 
will  show  varying  development  of  male  and  female  larvae  and  a 
very  great  difference  in  tinctorial  value. 
There  are  quite  a  number  of  grades  of  the  commercial  article 
and  it  is  usual  to  distinguish  but  two  grades  which  are  said  to  be 
due  to  a  difference  in  the  manner  of  killing  the  insects.  In  the  so- 
called  "  Silver  Gray  Cochineal."  the  freshly  collected  insects  are 
killed  by  heat  direct ;  whereas  the  "  Black  Cochineal  "  is  produced 
by  treating  the  insects  first  with  hot  water,  after  which  they  are 
dried.  It  is  supposed  that  part  of  the  wax  has  been  removed  by 
this  latter  treatment  and  that  the  silver  gray  variety  owes  its  color 
to  the  waxy  excrescence.  This  would  seem  to  be  borne  out  by  the 
fact  that  Liebermann 14  has  reported  that  the  silver  gray  variety 
contains  twice  as  much  wax.  which  he  named  coccerin.  He  found 
the  amount  of  wax  in  the  silver  gray  variety  to  vary  from  1.0  to  2.0 
per  cent.,  while  the  black  cochineal  gave  from  0.5  to  1.0  per  cent., 
and  in  one  sample  1.5  per  cent,  of  coccerin.  A  specimen  marked 
w  Granilla  yielded  4.2  per  cent,  of  wax.*  While  these  facts  are 
doubtless  true  it  will  be  found  that  the  coating  on  the  gray  cochineal 
consists  chiefly  of  mineral  matter,  as  was  first  observed  by  Leeu- 
wenhoek.2  If  a  few  of  the  grains  of  the  commercial  article  are  heated 
upon  a  slide  it  will  be  found  that  the  grayish  coating  scales  off  and 
is  not  destroyed  by  further  incineration  upon  the  lid  of  a  platinum 
crucible.    It  is  insoluble  in  water,  chloral  solution  or  benzole  and 
*  I  am  inclined  to  the  opinion  that  it  will  be  subsequently  found  that 
the  "  silver-gray  cochineal  "  consists  of  the  mother  insect  with  more  immature 
larvae  and  that  in  the  "'  black  cochineal "  the  larvae  are  more  fully  developed. 
