ADAiig°iS;  i9i3rm*}   Nature  and  Structure  of  Cochineal.  355 
about  an  acre  of  Nopal  plants  approximately  100  kilos  of  cochineal 
may  be  gathered;  this  would  represent  about  14,000,000  of  the 
membranous  cradles  with  larvae,  or  the  dried  insects  of  com- 
merce. 
The  Structure  of  the  Cochineal  Insect  of  Commerce. 
The  cochineal  of  commerce  consists  of  the  membranous  cradle 
of  the  female  which  is  removed  by  the  planters  from  the  Nopal 
plants.  They  are  then  subjected  to  steam  or  hot  water  and  dried, 
or  they  may  be  dried  by  direct  heat  as  will  be  referred  to  later. 
These  processes  it  has  been  supposed  are  necessary  in  order  to  kill 
the  female,  as  a  matter  of  fact  it  is  really  the  larvae  within  her 
which  are  destroyed,  as  will  be  seen  from  the  illustrations  used  in 
this  paper.  Before  one  can  study  the  nature  and  structure  of  the 
commercial  article,  which  is  of  a  dark  garnet  color  and  very 
opaque,  it  is  necessary  to  remove  the  coloring  matter.  This  is  best 
done  by  taking  a  convenient  quantity  of  the  cochineal,  say  about  10 
Gm.  and  macerating  it  with  100  c.c.  of  water  containing  2  or  3  per 
cent,  of  an  alkali.  The  mixture  is  allowed  to  stand  for  an  hour  or 
so,  the  contents  being  poured  over  a  piece  of  wire  gauze.  The 
insects  remain  on  the  gauze  and  are  then  washed  with  a  few  litres 
of  water.  The  insects,  from  which  the  coloring  matter  has  been 
partly  removed,  are  then  transfered  to  150  c.c.  of  hydrogen  per- 
oxide solution  and  allowed  to  stand  for  a  few  hours  with  occasional 
gentle  stirring.  The  mixture  is  again  transferred  to  the  gauze,  the 
excess  of  hydrogen  peroxide  being  washed  off  and  the  insects  trans- 
ferred to  a  weak  alkali  solution  in  which  they  are  macerated  for 
six  or  eight  hours.  The  mixture  is  poured  upon  the  wire  gauze 
and  washed  with  water  until  the  filtrate  runs  practically  colorless. 
The  insects  on  the  gauze  are  then  transferred  to  dilute  alcohol  to 
which  a  few  drops  of  hydrochloric  acid  have  been  added.  This 
now  renders  them  translucent  and  ready  for  microscopical  study. 
They  may  be  mounted  in  chloral  solution  or  a  solution  of  chloral 
and  glycerin  and  examined. 
The  material  which  has  been  cleared  in  this  way  shows  the 
cochineal  insect  to  be  a  hollow  vesicle  of  an  ovoid  or  plano-convex 
shape  having  in  the  upper  portion  some  of  the  remains  of  the 
mother  insect  (Fig.  1).  The  mouth  part  with  a  more  or  less  devel- 
oped beak  or  rostrum  is  always  present,  the  beak  sometimes  being 
extended  and  recurved  in  a  narrow  elliptical  form  in  the  direction 
