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XXXIV.  On  a  Species  of  Moth  found  inhabiting  the  Galls  of  a  Plant  near  to  Monte 
Video,    By  John  Curtis,  Esq.,  F.L.S.,  8fc.    Communicated  by  the  Secretary. 
Read  February  10,  1835. 
I  AM  induced  to  lay  the  following  observations  and  the  accompanying  drawing  before 
the  Society,  rather  with  a  desire  of  drawing  the  attention  of  those  naturalists  to  the 
subject  who  may  visit  the  country  from  whence  the  materials  were  brought,  than  with 
any  hope  of  being  able  to  explain  the  remarkable  facts  connected  with  the  ceconomy  of 
the  insect  which  is  the  object  of  these  investigations. 
Mr.  Howship,  who  first  showed  me  the  curious  galls  and  presented  me  with  speci- 
mens, informed  me  at  the  same  time  that  they  were  collected  by  Mr.  Earle,  who  accom- 
panied Captain  Fitzroy  in  the  Beagle  gun-brig :  he  found  them,  I  understand,  in  De- 
cember, on  a  spot  fifteen  miles  to  the  west  of  Monte  Video,  Rio  de  la  Plata.  The  plant 
bearing  the  galls,  which  Mr.  David  Don  thinks  may  be  a  species  of  Celastrus,  forms  a 
sort  of  underwood  shrub,  observed  only  in  that  part  of  the  country. 
The  branch  represented  at  B  (Plate  XL.)  shows  the  situation  of  two  galls  :  they  are 
frequently  smaller,  and  sometimes  five  or  six  are  clustered  together,  but  I  have  never 
seen  more  than  two  issuing  from  the  same  point.  Those  in  the  plate  are  wrinkled, 
owing,  I  suspect,  to  their  having  been  in  a  young  state  when  gathered,  for  many  of  the 
examples  are  smooth.  The  galls  arise  where  the  attachment  of  leaves  or  flowers  is  in- 
dicated, and  are  therefore  most  probably  produced  by  the  transformation  of  the  buds 
themselves.  On  the  side  of  the  gall  is  a  round  aperture,  with  an  operculum  beautifully 
fitted  to  it,  (Fig.  B,,  o.)  which  may  be  easily  picked  out  with  the  point  of  a  penknife  : 
this  operculum  is  equally  convex  with  the  rest  of  the  gall  and  is  of  the  same  thickness 
with  it,  but  the  diameter  of  the  inside  is  less  than  that  of  the  external  surface,  which 
forms  a  broader  rim  (Fig.  12,  o.).  In  Fig.  11.  the  operculum  has  been  removed  to 
show  the  orifice,  round  which  the  margin  is  thickened  and  a  little  raised.  At  Fig.  13. 
a  gall  is  divided  longitudinally,  showing  its  texture  and  the  internal  cavity,  with  the 
aperture  on  the  opposite  side,  from  which  the  operculum  has  been  removed.  At  Fig.  14. 
another  section  is  given  to  show  the  situation  of  a  pupa  that  is  attached  by  its  tail  to 
the  base,  with  its  head  close  to  the  operculum,  which  of  course  gives  way  by  a  slight 
expansion  or  elongation  of  the  pupa  when  the  insect  is  ready  to  hatch,  and  the  skin  is 
then  left  sticking  in  the  passage. 
Having  explained  the  structure  of  these  galls,  it  is  necessary  to  observe  that  many 
insects  belonging  to  the  order  Hymenoptera  have  the  power  of  forming  these  excrescences ; 
one  of  which,  the  Diplolepis  Gallee-tinctoria,  is  well  known  as  the  fly  causing  the  galls 
2  T  2 
