330 
•almost  entirely  without  leaves  and  without  flowers.  Elsewhere 
I observed  the  same  thing. 
This  ingenious  idea  of  Koebele  was  also  in  this  case  a complete 
success  and  will  lead  to  other  good  results  in  similar  cases. 
This  method  presents  very  grave  danger,  to  avoid  which  excep- 
tional and  able  caution  is  necessary  because  only  such  insect 
species  must  be  introduced  as  have  very  specialized  habits,  like  the 
Agromyza  and  Pterophorus,  which  almost  certainly  will  not  be 
able  to  adapt  themselves  suddenly  and  produce  the  same  changes 
in  plants  of  other  species. 
But  when  it  is  a question  of  insects  which  eat  or  mine  the 
leaves  or  sucking  insects  prudence  demands  a very  accurate  study 
because  it  might  happen  that  they,  when  transported  to  other 
regions,  would  adapt  themselves  to  other  plants  and  then  it  would 
become  necessary  to  have  recourse  to  the  introduction  of  their 
parasites  with  much  probability  but  without  certainty  of  their 
efficacy  in  the  new  home. 
In  Hawaii  none  of  the  species  introduced  by  Koebele  has  in- 
vaded other  plants  than  lantana,  only  specimens  of  Teleonemia 
bave  been  seen  on  some  local  plant,  but  without  staying  there  long 
and  with  reproducing;  therefore  I repeat,  for  the  present  Koe- 
bele’s  success  also  in  the  fight  against  a plant  which  had  become 
injurious  has  been  a complete  success. 
Lantana  was  introduced  also  in  New  Caledonia,  it  is  not  known 
when,  and  as  it  began  to  propagate  in  an  alarming  manner,  the 
insects  introduced  by  Koebele  in  Hawaii  were  asked  for,  a first 
shipment  has  been  made,  but  I do  not  know  the  result. 
UTILIZATION  OF  VERTEBRATES  FOR  THE  DESTRUC- 
TION OF  INJURIOUS  INSECTS. 
BIRDS. 
The  subject  of  the  greater  or  lesser  utility  of  insectivorous  birds 
has  been  much  debated  and  always  with  the  same  result,  that  is 
to  leave  everyone  with  the  opinion  he  had  before,  because  in  the 
case  of  indigenous  birds  it  is  very  difficult  to  appreciate  their  real 
value  and  therefore  the  few  facts  which  are  observed  are  used  by 
some  in  one  sense  and  by  others  in  a contrary  one.  I,  for  my 
part,  rather  believe  that  the  usefulness  and  the  harm  of  insecti- 
vorous birds  balance  each  other  and  that  more  frequently  the 
former  may  be  superior  to  the  latter,  considering  things  only 
from  the  view  point  of  immediate  agricultural  interest. 
There  always  have  been  and  there  still  are  so-called  ornithophils 
who  have  attributed  to  insectivorous  birds  a large  part  in  fighting 
injurious  insects  and  who  have,  besides  recommending  the  pro- 
tection of  indigenous  birds,  also  advocated  the  introduction  in 
other  regions  of  insectivorous  birds. 
About  the  middle  of  the  nineteenth  century  Acridotheres  tristis 
was  introduced  from  India  to  the  island  of  Mauritius,  became 
