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XXX.   On  Nycteribia,  a  Genus  of  Wingless  Insects.    By  J.  O.  Westwood,  Esq., 
F.L.S.,  Sfc.    Communicated  hj  the  Secretary. 
Read  November  25,  1834. 
In  every  group  of  animated  nature,  even  down  to  the  ranks  of  families  and  genera, 
there  exists  a  certain  number  of  objects  (generally  of  limited  extent)  which,  from  the 
anomalous  character  of  their  organization  with  reference  to  that  of  the  group  to  which 
they  naturally  belong,  have  not  ceased  to  perplex  the  systematist  as  to  their  true 
situation.  If  this  has  been  the  case  after  the  real  nature  of  their  organization  has 
been  made  known,  the  difficulty  has  been  far  greater  when,  unaided  by  the  light  of 
minute  analysis,  the  naturalist  has  contented  himself  with  a  rapid  prima  facie  exami- 
nation. 
Thus,  if  we  look  at  the  great  divisions  of  the  Animal  Kingdom,  we  find  the  Tunicata, 
Cephalopoda,  Zoanthida,  Cirripeda,  and  Annelida  affording  examples  of  such  groups. 
If  we  descend  a  step,  we  find  the  Pycnogonida,  Oniscida,  Stomapoda,  Nycteribia,  and 
the  Trilohites  oscillating  amongst  the  classes  of  the  Annulose  subkingdom ;  while  in 
like  manner  the  Strepsiptera  and  Dermaptera,  and  the  famiUes  Thripsidts  and  Pulicidce 
amongst  the  orders  of  the  Ptilota,  and  the  genera  Zoea,  Nehalia,  Hippa,  Mysis,  Limulus, 
Nymphon,  Galeodes,  &c.  amongst  those  of  the  Aptera,  have  afforded  endless  opportu- 
nities for  exercising  the  ingenuity  of  systematists.  To  carry  the  observation  still  lower 
among  the  families  of  an  order,  I  need  only  refer  to  such  genera  as  Omophron,  Urania, 
Xyela,  Trictenotoma,  Acentropus,  &c. 
With  respect  to  such  groups,  it  is  to  be  noticed  that  they  seem  to  be  generally  cha- 
racterized not  only  by  their  limited  extent,  bat  also  by  the  comparative  smallness  and 
rarity  of  the  objects  composing  them ;  and  that  they  appear  to  constitute  a  series  of 
stepping-stones  whereby  the  transition  from  the  structure  of  one  group  to  that  of  the 
adjoining  ones  is  effected,  many  of  them,  in  fact,  forming  the  osculant  groups  of  the 
'  Horse  Entomologicse'.  Another  peculiarity  seems  to  consist  in  the  generally  unat- 
tractive appearance  of  the  objects  of  which  they  are  composed,  which  has  caused  them 
(notwithstanding  the  great  interest  possessed  by  them  on  account  of  the  peculiarity  of 
their  characters)  to  be  comparatively  neglected  by  the  majority  of  authors. 
Among  these  groups,  perhaps  no  more  striking  instance  could  be  adduced  than  the 
genus  Nycteribia,  Latr.,  inasmuch  as  we  here  find  a  single  genus,  considered  as  oscu- 
lant, not  between  the  famihes,  or  even  the  orders  of  a  class,  but  between  two  of  the 
classes  themselves  of  the  Annulose  subkingdom  ;  thus,  while  Hermann,  in  his  '  Memoire 
VOL.  I.  2  o 
