Aug.  1,  1895,]  iiui^jnemmi  to  the  '^Tropical  Agriculturist^ 
■45 
!•  Protozoa,  represented  by  the  organism 
causing  pebrine.  It  is  a very  lowly  organised 
animal,  which  in  its  growing  condition  is  simply 
a mass  of  protoplasm  of  no  deliaite  shape  and 
of  microscopic  size.  It  tiually  becomes  spherical 
and  motionless,  and  the  whole  interior  becomes 
broken  up  into  a minute  mass  of  oval  spores. 
The  contents  of  each  spore  breaking  out  through 
one  end  of  the  spore  wall  and  beginning  to  feed 
and  grow,  completes  the  life  history  of  the 
animal.  All  the  organs  are  attacked,  and  besides 
being  hereditary  the  spores  are  scattered  over 
the  leaves  from  a diseased  insect  and  are  eaten 
by  the  others  with  their  food  and  thus  the 
disease  spreads. 
•2.  The  bacteria,  which  are  credited  with  most 
of  the  contgaious  diseases  of  man,  are  also  im- 
portant insect  parasites  and  may  be  represented 
by  the  disease  of  foul  brood.  These  are  very 
lowlj'  organised  plants,  increasing  almost  wholly 
by  simply  separating  into  two  equal  halves, 
growing  to  full  size  and  again  dividing,  and  so 
on,  tliougli  a few  produce  spores  occasionally. 
The  species  producing  insect  diseases  belong  to 
the  genera  micrococcus  and  bacillus,  the  former 
spherical  and  the  latter  cylindrical. 
3.  The  true  fungi,  such  as  produce  the  mus- 
cardine,  are  much  higher  developed  plants,  and 
two,  or  perhaps  three,  very  distinct  groups  are 
parasitic  on  insects.  They  all  have  this  in  common, 
that  they  are  composed  of  long  tlireads,  the 
mycelium,  and  short  round  or  oval  bodies,  the 
spores.  As  a ruie  the  spores  germinate  on  the 
surface  of  the  body ; the  plant  burrowing  its 
waj'  do  vn  into  the  insect  there  grows  till 
the  insect  dies,  and  then  again  passing  through 
the  .skin  produces  the  spores,  which  are  so 
conspicuous  on  insects  dying  from  these  diseases. 
The  spores  may  not  be  produced,  or  only  in 
limited  numbers,  when  the  weather  is  dry  or 
when  the  insect  is  so  small  as  to  dry  up  too 
soon.  In  tliese  cases  a splendid  crop  may  be 
produced  if  the  dead  insect  is  dropped  into  a 
bottle  partly  filled  with  water. 
The  fact  that  most  insects  lay  many  times, 
often  many  hundred  times  as  many  eggs  as  can, 
under  ordinary  conditions,  develop  to  maturity, 
is  quite  well  understood.  The  destruction  of  the 
great  majority  of  the  young  insects  is  chiefly 
accomplished  through  the  attack  of  their  natural 
parasites,  and  of  these  parasites  the  contagious 
diseases  are  by  all  odds  the  most  important.  My 
own  observations  at  Berkeley  for  three  years  are 
to  the  effect  that  at  least  nine  out  of  every  ten 
deaths  of  such  insects  due  to  parasites  are  caused 
by  some  form  of  contagious  disease.  For  these 
insects,  therefore,  nothing  else  determines  the 
abundance  or  scarcity  of  scale  insects  as  com- 
pletely as  do  contagious  diseases.  A very  little 
lessening  of  the  virulence  of  a disease  during 
any  season  will  enable  the  scale  to  overrun  the 
plants,  and  on  tlie  other  hand  a little  increase 
in  tlie  severity  of  the  attack  will  practically  an- 
nihilate the  scale  insects.  Kveryone  has  seen 
e.xamples  of  these  conditions.  I liave  repeatedly 
seen  cases  where  a dise.ise  was  particularly 
abundant  and  the  decrease  of  sc.iles  n-cribed  to 
some  useless  wash  or  to  lady-birds,  when  these 
latter  were  even  less  abundant  than  usual. 
Mistakes  of  this  kind  should  never  occur  with  a 
reliable  observer,  but  are  very  liable  to  occur  unless 
care  is  e.xercised.  This  is  especially  necessary 
when  a new  wash  or  insect  jiarasite  is  introduced. 
The  relation  of  lady-birds  to  diseases  is  well 
worthy  of  attention.  There  seems  to  be  evidence 
that  would  indicate  that  a great  increase  in  the 
numbers  of  our  native  species  of  lady-birds  follows 
or  is  as.sociated  with  a .serious  attack  of  some 
form  of  contagious  disease  on  scale  insect  or 
plant  louse.  This  apparent  relation  between 
lady-birds  and  disease  of  tlie  food  of  lady-bird.s, 
coupled  with  tlie  fact  that  the  relatives  of  the 
lady-birds  are  fungus  eaters  and  that  the  lady-birds 
themselves  were  once  undoubtedly  also  fungus 
eaters,  suggests  very  strongly  that  with  some 
species  at  least  disease  of  the  food  is  necessary 
to  great  lady-bird  increa.se. 
Another  point  in  reference  to  diseases  must  also 
be  considered.  There  must  be  some  means  of 
conveying  the  germs  of  a disease  from  insect  to 
insect.  While  the  scales  are  active  there  appears  to 
bo  sufficient  means  for  the  spread  of  the  disease.  It 
it  a fact  that  the  largest  number  usually  die 
soon  after  settling  and  have  apparently  become 
affected  while  active.  Those  that  have  escaped  the 
infliction  up  to  this  time,  however,  would  seem 
to  be  very  unpromising  subjects  for  the  disease, 
both  by  their  freedom  from  contact  and  on 
account  ot  their  special  means  of  protection. 
Now,  it  would  seem  that  lady-birds  serve  a very 
important  function  in  the  spread  of  the  diseases. 
Any  one  who  has  observed  the  actions  of  a 
lady-bird  either  while  it  is  a larva  or  an  adult 
will  have  noticed  that  it  does  not  settle  down 
and  devour  each  scale  it  comes  in  contact  with  ; 
instead,  it  has  the  habit  of  moving  restlessly 
about,  nibbling  here  and  there  and  only  now  and 
then  taking  a full  meal.  A better  arrangement 
for  spreading  diseases  could  not  be  desired  than 
this  habit  of  the  lady-bird.  Indeed,  tlie  relation 
of  the  ladybird  to  contagious  diseases  opens  a 
wide  fleld  for  study,  and  at  the  present  time  I 
know  of  none  in  the  whole  range  of  applied 
entomology  more  interesting  and  of  more  practical 
promise. 
♦ 
DAIRY  PICKINGS. 
The  Colonial  Veterinary  Surgeon  of  Cape  Colony 
writes  with  reference  to  the  occurrence  of  blood 
in  cows’  milk  : — If  it  is  real  blood  there  must 
be  rupture  of  some  small  blood  vessel  in  the 
glands  of  the  udder.  If  it  is  merely  a liloody- 
looking  sediment  whicli  appears  iii  the  milk 
especially  at  the  b ittom,  tliere  is  some  diseased 
condition  of  the  d iets  of  the  gland.  It  would 
be  as  well  to  a'Certain  first,  whether  it  is  in  one 
or  more  quarters  of  the  udder  ; this  could  easily 
be  done  by  milking  each  teat  into  a separate 
vessel,  and  if  it  is  found  to  be  in  one  only, 
the  milk  of  that  teat  could  be  thrown  away,  and 
the  milk  from  the  others  used.  Regarding  treat- 
ment, 1 would  recommend  that  the  cow  be  kept  in 
the  hou.se  or  in  a small  camp  where  she  would  not 
be  hustled  about  or  have  to  walk  too  much,  and 
relieve  the  udder  by  milking  her  thoroughly  dry 
three  times  a day.  E.vamine  the  udder  c.irefuily 
after  it  is  milked  out,  and  if  there  is  any 
undue  hardness  or  stiffness  about  any  of  the 
quarters,  bathe  it  with  warm  water  after  each 
milking  and  rub  on  some  fat  or  oil  over  the 
affected  quarter  immediately  after.  Rub  the  udder 
with  a pressing  motion  in  a downward  direction. 
