AlAuSf9hi3!m'}  Nature  and  Structure  of  Cochineal.  357 
by  Mayer  10  on  living  material  and  termed  by  him  "  wax-pores." 
In  the  body  of  the  insect,  especially  those  in  which  the  larvae  are 
very  young,  there  are  usually  seen  somewhat  broad,  more  or  less 
vermiform  segments  running  more  or  less  transversely  or  obliquely 
and  these  may  represent  portions  of  the  digestive  tract  (Fig.  1). 
In  the  abdominal  region  which  is  very  large  the  larvae  are  borne 
(Figs.  1,  3),  and  these  usually  are  seen  to  be  in  several  stages  of 
development. 
The  larvae  vary  on  an  average  from  about  300  to  500  microns  in 
length.  When  the  antennae  and  legs  have  emerged  the  larvae  are 
more  than  1  mm.  in  length.  When  very  young  they  are  more  or 
less  ellipsoidal  or  ovoid  and  very  soon  are  characterized  by  a  pair 
of  coils  which  are  closely  wound  and  form  the  beak  or  rostrum 
(Fig.  4).  These  coils  represent  the  proboscis  or  sucking  appa- 
ratus and  are  frequently  seen  uncoiled  or  protruding  (Fig.  6)  and 
are  composed  of  4  threadlike  parts  which  pair  off  into  2  coils,  the 
one  surrounding  the  other.  The  inner  pair  of  these  threads  forms 
the  sucking  apparatus  while  the  outer  acts  as  a  cutting  instrument. 
By  means  of  this  long  threadlike  proboscis  the  insect  is  enabled  to 
penetrate  the  thick  tissues  of  the  cactus  plant  and  obtain  the  neces- 
sary nourishment.  The  body  is  otherwise  covered  with  short 
conical  hairs  about  20  microns  in  length,  the  apex  being  truncate. 
Microscopic  mounts  usually  show  in  the  abdominal  region  of  the 
larvae  numerous  crystals  in  the  form  of  rods  or  spherical  aggre- 
gates, and  which  are  probably  wax  crystals.  In  older  insects  when 
the  legs  have  more  or  less  protruded  the  antennae  are  usually  more 
or  less  outspreading  (Fig.  5).  The  legs  vary  from  400  to  600 
microns  in  length  and  consist  of  from  3  to  8  segments,  the  lower 
pair  having  the  greater  number.  They  are  provided  at  the  joints 
with  a  few  bristlelike  hairs  which  vary  from  25  to  60  microns  in 
length.  The  antennae  are  about  200  microns  in  length  and  con- 
sist of  from  6  to  8  parts,  being  like  the  legs  somewhat  bristly 
hairy  at  the  joints.  The  body  of  the  matured  young  insect 
shows  the  numerous  wax-pores  already  referred  to  as  occur- 
ring on  the  mother  and  also  in  the  lower  abdominal  region  a 
differentiation  into  9  or  10  segments  (Figs.  3-5). 
The  Red  Coloring  Principle. 
The  red  coloring  principle,  carminic  acid,  is   found  appar- 
ently altogether  in  the  larvae  enclosed  in  the  body  of  the  mother 
insect.   This  is  present  to  the  extent  of  about  10  per  cent.  Accord- 
