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MR.  J.  O.  WESTWOOD  ON  NYCTERIBIA. 
lations,  let  us  examine  the  statements  of  authors  as  to  the  structure  of  this  part  of  the 
body  in  the  previously  recorded  species  of  the  genus. 
Hermann  describes  three  kinds  of  individuals.  The  first,  to  which  he  applies  the 
specific  name  of  Vespertilionis,  has  the  abdomen  obovate,  convex,  and  attenuated  behind, 
with  the  terminal  segment  entire  and  rounded  at  the  extremity,  and  furnished  beneath 
with  a  pair  of  incurved  styles.  He  also  describes  minutely  another  organ,  which,  upon 
compression,  "sort  entre  les  deux  avant-derniers  anneaux,"  of  a  fleshy  substance,  ter- 
minated by  two  small  oval  lobes,  and  from  the  extremity  of  which,  upon  further  pressure 
being  applied,  another  organ  was  protruded,  furnished  beneath  with  a  curved  seta.  The 
second  kind  of  individuals  were  regarded  by  him  as  specifically  identical  with  the  former, 
difl'ering  only  in  having  the  last  segment  deeply  emarginate  and  simple :  the  body  also 
seemed  larger,  and  the  legs  shorter.  In  this  species  the  cilia  of  the  extremity  of  the 
basal  abdominal  segment  are  continued  along  the  upper  side  of  this  part  of  the  body  as 
well  as  beneath.  Now  it  is  evident  that  the  individuals  first  described  were  males,  not 
only  from  the  articulation  of  the  abdomen,  but  from  the  possession  of  an  exserted  mas- 
culine apparatus  ;  but  the  other  individuals  (of  which  Hermann  had  only  two  old  dried 
specimens),  in  the  simple  and  emarginate  character  of  the  abdomen,  seem  to  approach 
the  females  of  Nyct.  Latreillii  subsequently  described  :  and  it  is  to  be  observed  that 
Hermann  does  not  state  that  their  abdomen  was  articulated  like  that  of  the  former,  but 
merely  points  out  the  characters  in  which  they  were  observed  to  differ.  Neither  does 
he  give  any  opinion  as  to  the  sexes  of  his  insects'.  His  third  kind  of  individuals, 
specifically  named  biarticulatum,  precisely  agree  with  Montagu's  species,  described  by 
Dr.  Leach  under  the  trivial  name  of  Hermanni,  having  a  pair  of  exserted  styles  at  the 
superior  extremity  of  the  abdomen.  Latreille  seems  entirely  to  have  overlooked  Her- 
mann's description  of  the  latter  insect  in  his  account  of  the  structure  of  the  genus, 
assigning  to  Hermann's  second  kind  of  individuals  a  character  not  stated  by  Hermann, 
namely,  that  of  the  abdomen  being  eight-jointed,  and  giving  the  biarticulatum  as  the 
male  of  his  Nyct.  Vespertilionis.  Dr.  Leach,  evidently  taking  his  characters  from  his 
Hermanni,  thus  describes  ih.e  abdomen  :  "In  utroque  sexu  8-articulatum. — Foeminae? 
segmento  primo  dorsali  producto,  segmenta  quatuor  sequentia  tegente  ;  segmento  ultimo 
stylo  apice  setigero  instructo  ; — Maris  ?  segmento  ultimo  majore."  And  his  figure  of 
the  supposed  female  of  his  Hermanni  represents  an  insect  with  a  large  elevated  and 
produced  basal  abdominal  segment,  the  remainder  of  the  abdomen,  being  the  smaller 
portion,  appearing  inarticulate,  and  terminated  by  two  long  recurved  piliferous  diverging 
styles  :  the  figure  of  the  other  sex  lias  the  abdomen  six-jointed,  the  last  joint  being  large 
'  M  xXk  abdomen  in  this  second  kind  of  individuals  were  really  articulated,  as  in  the  former,  I  should  feel  little 
hesitation  in  regarding  them  as  the  males,  probably  of  a  different  species,  in  which,  from  the  dried  and  shrivelled 
•tatf  of  the  Hpecimcns,  the  male  organs  had  become  closely  applied  to  the  under  surface  of  the  body,  and  the 
terminal  ucgmcnt,  for  the  sume  reason,  had  l)ecome  emarginate. 
