2(S4  AniiKal  Report  for  lUOl  of  the  Zoologist. 
terribly  destructive  creature.  It  is  as  well  to  repeat  the  caution 
that  the  few  mites  on  a young  plant,  which  are  enough  to 
constitute  a future  dangei',  may  escape  the  most  careful  exami- 
nation, and  that  the  only  real  safeguard  is  the  freedom  from 
disease  of  the  parent  plant  from  which  the  cuttings  were 
taken. 
Complaints  were  received  with  regard  to  two  other  acarine 
pests  which  appear  to  be  very  destructive  in  hothouses.  They 
belong  to  a group  of  mites  with  which  few  people  have  any 
acquaintance,  and  with  regard  to  which  the  little  that  has  been 
written  is  not  easily  accessible.  They  are  discussed  in  the 
succeeding  section. 
MITES  OF  THE  GENUS  TARSONEMUS  WITH  A 
DESCRIPTION  OF  TWO  NEW  SPECIES. 
It  has  been  suspected  for  some  time  past  that  mites  of  the 
obscure  genus  Tat'ffonemus  are  a frequent  cause  of  disease  in 
plants.  They  are  so  small  and  so  difficult  to  investigate  that 
very  little  attention  has  been  paid  to  them.  There  are  probably 
many  species,  but  very  few  have  been  described,  and  about 
these  little  is  known.  It  seejns  likely  that  many  of  the 
diseases  to  which  hothouse  plants  are  subject  are  due  to  these 
mites,  and  my  attention  was  directetl  to  the  matter  this  autumn 
by  the  receipt  of  two  batches  of  diseased  plants  from  nurseries, 
the  cause  of  injury  in  each  case  being  a mite  of  the  genus 
TarsoHemus.  It  seems  important,  therefore,  to  attempt  to 
bring  together  what  is  already  known  about  these  creatures 
and  to  add  any  facts  which  have  been  observed  in  the  cases 
under  notice,  though  little  can  be  said  at  present  with  regard  to 
their  treatment. 
The  Tarsonemidae  constitute  a sub-order  of  the  acari  or 
mites — the  Heterostigmata.  They  are  very  small,  averaging, 
perhaps,  the  hundred-and-twentieth  of  an  inch  in  length.  The 
males  and  females  are  very  different  in  appearance  and  might 
easily  be  taken  for  entirely  different  species.  The  integument 
covering  the  female  is  divided  into  ^Dlates  which  overlap,  like 
the  slates  on  a house  roof,  though  these  are  extremely  difficult 
to  make  out,  and  this  apparent  segmentation  is  a phenomenon 
quite  unusual  in  the  mite  tribe. 
In  both  sexes  the  first  and  second  pair  of  legs  are  directed 
forward  and  are  widely  separated  from  the  third  or  fourth 
pairs  which  are  directed  backwards.  The  genus  Tarsone?)ius 
can  be  recognised  at  once  by  the  form  of  the  fourth  pair  of 
legs.  In  the  female  these  are  extremely  thin  and  weak  and 
end  in  two  long  bristles.  In  the  male  they  are  strong  clasping 
organs  not  used  for  locomotion  at  all,  but  dragged  behind  the 
animal  as  it  moves  alons. 
