358  Nature  and  Structure  of  Cochineal. 
ing  to  Mayer  10  it  occurs  in  drops  near  the  periphery  of  the  cells  of 
the  fatty  body,  the  drops  being  less  numerous  in  the  case  of  the 
male  insect.  It  also  occurs  in  the  yolks  of  the  eggs  and  in  the 
diffuse  fatty  body  in  the  new  hatched  larvae.  Mayer  says  that  the 
pigment  does  not  occur  in  the  gut,  but  in  another  place  he  states 
that  it  moderately  colors  the  feces,  which  anomaly  he  does  not 
attempt  to  explain.  It  is  possible  that  he  may  mean  that  the  pig- 
ment is  not  found  in  the  anterior  part  of  the  gut,  but  is  introduced 
into  it  by  the  Malpighian  tubules.  As  to  function  of  the  carminic 
acid  Mayer  has  no  suggestion  to  offer,  but  is  of  the  opinion  that 
the  pigment  is  intrinsic  and  not  derived.  On  the  other  hand. 
Krukenburg  11  considers  that  the  carminic  acid  is  a  reserve  product, 
basing  his  opinion  on  the  theory  that  the  female  contains  this  prin- 
ciple in  from  26  to  50  per  cent,  of  her  body  weight.  He  also  con- 
sidered the  pigment  to  be  of  a  glucosidal  nature,  and  expresses 
the  view  that  glucosides  are  in  the  nature  of  reserve  principles. 
But  it  has  since  been  shown  14  that  the  coloring  principle  in  cochi- 
neal is  not  a  glucoside.  Marion  I.  Xewbigin  12  states  that  it  is 
impossible  to  decide  the  question  of  the  function  of  the  coloring 
principle  of  cochineal  as  yet,  but  that  the  association  of  a  pigment 
in  the  cells  of  a  fatty  body  is  not  unknown  among  other  insects  and 
mentions  the  case  of  Luciola.  Mayer  also  describes  a  colorless 
crystalline  substance  occurring  in  the  cells  containing  the  red  pig- 
ment but  does  not  discuss  the  nature  of  these  crystals.  Xewbigin 
states  that  they  may  be  urates  and  if  so  the  contrast  between  the 
pigmentation  of  the  sexes  in  Luciola  and  Coccus  is  striking  in  the 
extreme.  As  a  matter  of  fact  the  colorless  crystals  are  probably 
of  the  wax,  coccerin,  and  are  quite  common  in  preparations  made 
for  microscopic  work  as  has  already  been  pointed  out. 
While  the  theory  of  Mayer  in  regard  to  the  function  of  car- 
minic acid  is  probably  nearer  the  truth,  Gierke 13  states  that  the 
coloring  substance  in  cochineal  is  produced  in  the  body  of  the  insect 
and  appears  to  be  in  the  form  of  a  uniform  purplish-colored  sap. 
He  found  this  sap  on  microscopical  examination  to  be  nearly  color- 
less and  to  contain  numerous  small  purplish-colored  granules  to 
which  he  ascribed  the  color. 
Throughout  the  literature  there  are  very  many  statements  that 
the  same  coloring  principle  found  in  Coccus  Cacti  is  present  in  other 
species  of  Coccus.  This  is  considered  to  be  doubtful  and  requires 
confirmation.    It  is  rather  interesting  to  note  that  while  the  wider 
