Mites  of  the  Genus  Tarsonemus. 
287 
3.  T.  tjuj-i  Caiiestrini  and  Bcrlese,  Atti  del  Sue.  Veneto-Trentina  di  Sci.  dVdt., 
Vol.  1),  page  8,  1884.  Found  on  box  leaves. 
4.  'J'.  y/’yre/e  Targioni-Tozetti,  Annali  delV Agricultural  Vol.  1,  1878.  Found 
in  diseased  rice.  Male  unknown. 
5.  T.  minusculux  Canestrini  and  Fanzago,  t.c.  Found  on  the  body  of 
another  mite.  Male  unknown. 
().  T.  iqnrifex  Marchal,  Bull.  Sue.  But.  Fr.,  1902.  Found  on  diseased  oat 
plants. 
The  Ta7'sunemus  mite  on  the  fern  is  described  as  being 
immensely  more  difficult  to  get  rid  of  than  “ red  spider,”  and 
my  correspondent  says  that  he  has  tried  “ all  the  known 
insecticides  and  fumigators  in  commerce  ” without  effect. 
Carbon  bisulphide  fumes  and  hydrocyanic  gas  have  pi’oved 
powerless  against  the  mite,  and  this  is  the  more  remarkable  as 
the  creature  is  by  no  means  so  efficiently  protected  as  is  the 
case  with  the  black-currant  gall  mite  for  instance,  but  it 
seems  to  possess  extraordinary  vitality  and  tenacity  of  life. 
Moreover,  it  is  so  small  as  to  be  easily  overlooked,  and  for  the 
most  part  when  the  plants  present  a distinctly  diseased  con- 
dition the  attack  is  already  over  and  few  if  any  of  the  mites 
are  to  be  foxind. 
Mr.  Lynch,  Superintendent  of  the  Botanical  Gardens  at 
Cambridge,  tells  me  that  this  is  the  case  with  the  begonia 
mite,  and  that  instead  of  fumigating  the  obviously  diseased 
plants  the  only  safe  way  is  to  fumigate  all  new  plants,  though 
they  may  appear  quite  healthy,  before  introducing  them 
into  the  houses.  In  the  light  which  experiments  have 
thrown  on  the  resisting  powei’  of  the  mite  to  all  ordinary 
insecticides  it  seems  unlikely  that  even  this  measure  would 
be  entirely  successful,  but  it  would  at  all  events  stand  a better 
chance  when  the  mites  are  few  in  number  and  the  leaves  are 
not  dotted  with  eggs,  which  are  always  difficult  to  kill.  Badly 
diseased  plants  should  be  removed  and  burnt,  but  it  is  hoped 
that  further  investigation  will  lead  to  some  way  of  arresting 
the  disease  in  its  early  stages. 
Cecil  Warburton. 
Zoological  Laboratory, 
Cambridge. 
