MR.  J.  O.  WESTWOOD  ON  NYCTERIBIA. 
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term  he  also  in  like  manner  applies  to  the  two  protruded  lateral  organs  of  the  mouth 
of  the  Hippoboscidce.  That  these  organs  are  perfectly  analogous,  Latreille  had  long  ago 
implied  by  describing  them  both  under  the  same  dubious  appellation,  "palpi?"  As 
to  their  real  analogies  among  the  organs  of  a  mandibulated  mouth,  I  however  offer 
no  opinion,  observing  only  that  in  defending  the  delicate  central  inferior  spiculate  ap- 
paratus of  the  mouth,  they  appear  to  perform  the  functions  of  the  articulated  sheath  of 
the  rostrum  of  the  Hemiptera.  This  apparatus  of  the  lower  part  of  the  mouth  of  Nyc- 
teribia  consists  at  first  sight  of  a  large  basal  bulb-hke  organ,  terminating  in  an  elon- 
gated slender  and  horny  style,  precisely  similar,  in  fact,  to  the  same  organ  in  Hippobosca. 
On  each  side  of  the  base  of  the  style,  in  the  species  under  examination,  there  are  two 
or  three  fine  hairs  as  long  as  the  style  itself.  The  style  in  two  individuals  appeared  to 
be  composed  of  two  demi-sheaths,  although  in  the  other  specimen  it  formed  only  a  single 
undivided  canal,  which  from  analogy  with  Hippobosca  is  evidently  its  real  construction. 
It  is  not  a  simple  organ,  but  contains,  like  its  representative  in  Hippobosca,  several  setce. 
I  found  that  it  inclosed  at  least  two  seta,  of  equal  length  with  the  canal  itself,  one  of 
which  was  more  robust  than  the  other ;  indeed  in  one  specimen  the  more  robust  one 
appeared  divisible  into  two  seta,  while  in  another  this  was  not  only  the  case,  but  the 
more  slender  one  also  presented  the  same  appearance.  Analogy,  however,  with  Hip- 
pobosca would  induce  us  to  suppose  that  there  are  but  two  seta,  as  above  described, 
inclosed  in  the  canal.  Latreille,  quoting  the  observation  of  Hermann  that  he  had  not 
clearly  observed  the  structure  of  the  mouth,  but  had  noticed  four  palpi,  two  short  and 
thick,  and  two  longer  and  more  slender,  excuses  the  supposed  inaccuracy  of  that  author 
on  account  of  the  minuteness  of  the  animals.  It  is  evident,  however,  from  Hermann's 
figures  that  the  two  short  and  thick  organs  were  the  antenna. 
The  thorax  exhibits  a  very  remarkable  structure.  It  is  flat,  and  of  a  form  somewhat 
between  oval  and  round  ;  its  upper  surface  is  of  a  whitish  coriaceous  substance,  divided 
into  compartments  by  narrow  crustaceous  ridges.  This  structure  was  admirably  de- 
scribed by  Linnaeus  under  the  term  "thorax  angulatus  cruciatus  ;"  notwithstanding 
which,  Hermann,  evidently  judging  from  the  inaccurate  figures  referred  to  by  Linnaeus, 
conceived  that  the  description  was  not  intended  by  that  author  for  an  insect  of  this 
genus.  The  inferior  surface  extends  in  a  plate  beneath  the  place  of  insertion  of  the 
legs,  the  femora  of  which  are  consequently  prevented  from  being  brought  below  the 
level  of  the  under  surface  of  the  thorax,  although  they  possess  a  considerable  power  of 
upward  motion,  this  being  effected  by  the  soldering  of  the  coxa  and  trochanters  of  the 
four  hind  legs  with  the  dorsal  region  of  the  thorax,  whereby,  as  Latreille  observes,  the 
back  of  the  thorax,  in  fact,  becomes  the  breast.  On  examining  the  anterior  and  su- 
perior extremity  of  the  thorax,  a  minute  raised  line  is  seen  to  extend  in  a  curved  direc- 
tion on  the  outside  of  the  base  of  the  fore  legs,  immediately  behind  the  place  of  in- 
sertion of  the  head,  somewhat  in  this  shape,<^.  Taking,  therefore,  into  consideration 
