The feeding behaviour of Pharoscymnus numidicus (Coccinellidae), predator of the date palm scale Parlatoria blanchardi


Kehat, M.

Entomologia Experimentalis et Applicata 11(1): 30-42

1968


The following is virtually the author's summary. The searching capacity of Pharoscymnus numidicus (Pic), determined in the laboratory in Israel by criteria of mobility and survival rates, increased with the age of the larvae. The searching pattern was of a random nature; the predator did not orientate towards its prey, Parlatoria blan-chardii (Targ.), and the direction of its movements was influenced by physical factors such as light. The ability to feed on alternative foods increased the chances of survival under conditions of natural food scarcity. In this respect, the cannibalistic behaviour of the Coccinellid is of particular importance. Its feeding capacity was dependent on instar, sex, history of the larvae in relation to amounts of food previously consumed, temperature and the population density of the host insect.

Ent.
exp.
&
appi.
11
(1968):
30
12.
North-Holland
Publishing
Co.,
Amsterdam
THE
FEEDING
BEHAVIOUR
OF
PHAROSCYMNUS
NUM1DICUS
(COCCINELLIDAE),
PREDATOR
OF
THE
DATE
PALM
SCALE
PARLATORIA
BLANCHARD!'
BY
M.
KEHAT
Div.
of
Entomology,
The
Volcani
Institute
of
Agricultural
Research,
Bet
Dagan,
Israel.
The
searching
capacity
of
Pharoscymnus
numidicus,
determined
by
criteria
of
mobility
and
survival
rates,
increases
with
age
of
larvae.
The
searching
pattern
is
of
a
random
nature;
the
predator
does
not
orientate
toward
its
prey,
and
the
direction
of
its
movement
is
influenced
by
physical
factors
such
as
light.
The
ability
to
feed
on
alternative
foods
increases
the
predator's
chance
to
survive
under
natural
food
scarcity
conditions.
In
this
respect,
its
can-
nibalistic
behavior
is
of
particular
importance
for
survival.
The
feeding
capacity
is
dependent
on
instar,
sex,
history
of
larvae
in
relation
to
amounts
of
food
previously
consumed,
at-
mospheric
temperature,
and
population
density
of
the
host
insect.
Pharoscymnus
numidicus
Pie.
is
one
of
the
most
important
predators
of
the
date
palm
scale
(Parlatoria
hlanchardi
Targ.)
in
Israel.
Its
distribution,
fecundity,
fertility,
resistance
to
unfavorable
conditions,
and
synchronization
with
prey
have
been
investigated
(KEUAT,
1966;
1967a,
b).
Other
important
factors
which
should
be
taken
into
consideration
when
the
efficiency
of
a
natural
enemy
is
evaluated
are
searching
capacity
and
feeding
rates.
Such
information,
concerning
other
Coccinellidae,
is
readily
available
(BANis,
1954, 1956;
DIXON,
1959;
HAGEN,
1962;
HODEK,
1957,
1967;
KADDOU,
1960;
SMITH,
1965);
however,
with
regard
to
Pharoscymnus
numidicus,
our
knowledge
is
extremely
limited.
MATERIALS
AND
METHODS
The
searching
capacity
of
the
insect
was
determined
by
studying
its
mobility,
its
longevity
and
its
power
of
perception.
In
the
experiments
designed
to
study
mobility,
a
larva
or
adult
was
released
in
the
approximate
center
of
a
uniformly
illuminated
searching
area
(50
X
50
cm)
and
its
path
was
traced
with
a
pencil.
The
total
period
of
each
test
was
5
min.
The
length
of
path
was
measured
and
the
speed
was
calculated
in
cm/min
In
order
to
study
the
power
of
perception,
the
behaviour
of
the
coccinellid
was
observed
in
the
searching
area,
where
Parlatoria
scales
were
randomly
distributed.
The
phototactic
response
and
attraction
of
adults
to
different
wave
lengths
of
Contribution
from
The
National
and
University
Institute
of
Agriculture
Bet
Dagan,
Israel.
1967
Series;
No.
1200-E.
FEEDING
BEHAVIOUR
OF
PREDATOR
OF
SCALE
31
the
spectrum
were
recorded
by
keeping
adults,
which
had
been
starved
for
24
hours,
in
cages
(5
cm
diam.,
10
cm
long)
illuminated
through
a
2
mm
hole
with
different
filters
(Fig.
1).
The
percent
transmission
of
the
different
wave
lengths
through
the
different
filters
was
recorded
by
a
Beckman
apparatus.
After
1
1
/
2
hours
the
number
of
individuals
attracted
through
the
hole
was
counted.
The
temperature
in
the
cages
fluctuated
between
31
and
34°
C;
the
average
global
radiation
of
sunlight
during
the
experiments
was
181-195
g/cal/cm
2
/rnin.
hole
filter
Fig.
1.
Cage
us&d
for
determining
the
attraction
of
adults
to
different
wage
lengths
of
the
spectrum.
The
starvation
longevity
of
larvae
and
adults
was
determined
by
caging
them
singly,
and
keeping
them
without
food
until
death.
All
larvae
and
adults
used
in
the
experiments
had
just
hatched,
moulted
or
emerged
and
had
no
access
to
food
immediately
thereafter.
All
cages
(plexiglass,
10
mm
diam.,
6
mm
high)
were
ventilated
and
maintained
at
constant
levels
of
temperature
(27°
C)
and
relative
humidity
(75%).
Increase
of
survival
by
feeding
on
alternative
nutrients
was
examined
by
offering
different
prey
insects.
Also
experiments
were
conducted
studying
the
difference
between
rates
of
cannibalism
among
the
different
stages
by
confining
them
together
in
small
cages.
To
investigate
cannibalism
of
newly
hatched
larvae
on
eggs,
single
larvae
were
supplied
with
certain
numbers
of
eggs,
and
the
larval
delevopment
was
followed.
In
experiments
on
larval
cannibalism
on
other
larvae
of
the
same
age
or
on
pupae,
only
two
individuals
were
put in
a
cage.
Cannibalism
tests
involved
mobile
larvae
only.
Therefore
the
results
may
not
reflect
further
cannibalism
when
some
of
the
larvae
are
moulting.
The
feeding
capacity
was
examined
by
rearing
single
larvae
and
adults
of
the
predator
on
females
or
nymphs
of
P.
blanchardi
in
cages
illustrated
in
Fig.
2.
The
rate
of
prey
consumption
was
recorded
under
conditions
of
both
food
abundance
and
food
scarcity.
RESULTS
AND
DISCUSSION
Searching
behaviour
As
the
adults
of
P.
numidicus
usually
do
not
fly,
the
searching
ability
of
this
predator
depends
mainly
on
the
speed
of
its
crawling.
First
instar
larvae
being
32
M.
KEHAT
a
b
C
a
!1):
e
ll
0 0
,
I
b
a.
C
C
Water
A.
Plexigiass
B.
Cellophane
paper
C.
Date
pintme
infested
with
Parlatoria
Fig.
2.
Diagram
illustrating
the
construction
of
the
cells
used
for
determining
the
feeding
capacity
of
Pharoscymnus
numidicus.
very
slow
crawling,
are
somewhat
limited
in
finding
the
prey
and
consequently
may
easily
starve
to
death.
The
mobility
and
consequently
the
efficiency
of
prey
search-
ing
increased
with
larval
development
and
was
highest
in
the
adult
stage
(Table
I).
In
the
absence
of
flight,
this
predator
is
therefore
somewhat
restricted
in
its
ability
to
disperse
and
to
find
new
sources
of
food,
but,
on
the
other
hand,
very
dense
populations
of
the
predator
are
attained
once
it
reaches
its
prey.
The
searching
pattern
is
random.
The
larvae
and
adults
often
searched
rather
thoroughly
in
areas
already
visited
by
them,
and
left
some
others
unvisited.
There
were
no
directional
movements
which
led
the
predator
toward
its
prey,
and
chance
played
the
main
role.
Both
larvae
and
adults
found
the
prey
only
after
physical
contact
had
been
made.
It
seems
that
the
predator
lacks
the
power
of
host
percep-
100
90
80
0---
ct
/
.
70
,
i
i
60
50
30
20
10—
I
ah,
a
ttra
c
te
d
ph
tran
sm
is
s
ion
FEEDING
BEHAVIOITR
OF
PREDATOR
OF
SCALE
33
TABLE
I
Speed
of
crawling
(cm/min.)
of
Ph.
nut
-
adieus
larvae
and
adults
(27°
C,
75%
R.H.)
(10
individuals
of
each
stage
were
examined)
Stage
Average
Range
Stage
Average
Range
First
instar
larvae
4.8
4.1—
6.8
Fourth
instar
larvae
24.0
21.0-29.0
Second
instar
larvae
15.0
11.0-17.0
Starved
adults
1
)
33.0
30.0-40.0
Third
instar
larvae
20.0
19.0-21.0
Well-fed
adults
hardly
moves
1
)
Starved
for
24
hours
before
the
test.
60
50
40
30
20
10
white
ultraviolet
violet
blue
yellow
red
no
light
350
400
450
500 550
600
650
700
750
Wave
length
40
Fig.
3.
Percent
transmission
of
different
wave
lengths
through
the
filters
used
in
the
experi-
ment
(bottom)
and
percent
of
beetles
attracted
to
different
wave
lengths
(top).
34
M.
KEHAT
tion
over
distances.
This
has
also
been
shown
for
some
other
Coccinellidae
(BANKS,
1954;
DIXON,
1959;
HAGEN,
1962;
HODEK,
1967
and
KADDou,
1960).
The
direction
of
movements
may
be
influenced
by
light.
The
adults
were
positi-
vely
phototropic
to
the
short
rays
of
the
spectrum.
There
was
some
attraction
also
to
violet
and
blue
rays
but
this
was
due
to
the
transmission
of
some
UV
rays
through
these
filters.
The
percent
of
beetles
attracted
was
always
higher
as
the
rate
of
the
UV
rays
transmitted
through
the
filter
rose
(Fig.
3).
Starvation
survival
The
starvation
survival
increased
with
age
of
larvae.
Short
longevity,
in
ad-
dition
to
the
larvae's
slowness,
is
also
a
factor
restricting
the
searching
capacity
of
first
instar
larvae.
When
starved,
fourth
instar
larvae
showed
a
higher
survival
rate
than
adults
(Table
11).
The
survival
of
the
adults
was
negatively
correlated
with
temperature
(Table
HI).
The
shortening
of
the
adult's
longevity
at
higher
temperature
need
not
necessarily
restrict
its
searching
capacity,
as
its
higher
activity
at
those
temperatures
may
compensate
for
its
shorter
life.
TABLE
H
Starvation
longevity
of
larvae
and
adults
of
Ph.
numidicus
(27
C,
75%
R.H.)
(15
individuals
of
each
stage
were
examined)
Stage
Average
Range
Stage
Average
Range
(days)
(days)
(days)
(days)
First
in
star
larvae
3.4
3-4
Fourth
instar
larvae
11.3
8-14
Second
instar
larvae
5.1
5-6
Adults
6.5
5—
8
Third
instar
larvae
6.5
6-7
TABLE
III
The
influence
of
temperature
on
the
longevity
of
starved
Ph.
numidicus
adults
(75%
RR.)
{At
each
temperature,
15
individuals
were
examined)
Temperature
Average
Range
Temperature
Average
Range
C)
(days)
(days)
(°C)
(days)
(days)
15
15.2
9-24
27
6.5
5----8
20
11.2
9-16
29
5.0
4-7
Alternative
food
In
the
absence
of
its
natural
prey,
the
predator
was
capable
of
increasing
survival
by
feeding
on
alternative
food
such
as
Prodenia
litura
eggs,
aphids
(Brachycaudus
amygdulinus
Sehout),
mites
(Tetranychus
cinnabarinus
Boisd.),
and
aphid
honey-
dew.
These
types
of
food
were
nutritionally
deficient
for
egg
production.
When
feeding
on
Prodenia
eggs,
the
insect
could
develop
from
first
instar
to
the
adult
stage.
This
has
also
been
shown
for
Coccinella
I
I-punctata
(11311.
I-um,
1955).
Under
conditions
of
food
scarcity,
cannibalism
is
of
particular
importance
for
Cannibalism
Cannibalistic
stage
Stage
exposed
to
cannibalism
First
instar
larva
Second
instar
larva
Third
instar
larva
Fourth
instar
larva
Adult
First
instar
larva
Third
instar
larva
Adult
First
instar
larva
Second
instar
larva
Third
instar
larva
Fourth
instar
larva
Fourth
instar
larva
Adult
Adult
Be
tween
t
he
o
E
a.)
E
C
1
)
0.0
-
r
])
egg
egg
egg
egg
egg
pupa
pupa
pupa
First
instar
larva
Second
instar
larva
Third
instar
larva
Fourth
instar
larva
Second
instar
larva
Adult
Third
instar
larva
FEEDING
BEHAVIOUR
OF
PREDATOR
OF
SCALE
35
survival.
A
high
degree
of
cannibalism
was
observed
only
in
those
experiments
in
which
larvae
or
adults
were
kept
together
with
eggs.
Pupae
were
highly
resistant
to
larval
or
adult
attacks,
apparently
due
to
their
protective
integument.
The
degree
of
cannibalism
between
larvae
of
the
same
instar
was
small
(Table
IV).
Feeding
on
eggs,
even
when
larvae
were
supplied
with
only
a
small
number
of
eggs,
increased
the
survival
rate
of
the
first-instar
larvae
(Table
V),
and
enabled
larvae,
TABLE
IV
Rate
of
cannibalism
between
the
different
stages
of
Ph.
numidicus
(27°
C,
75%
R.H.)
Combinations
of
cannibalism
examined
No.
of
replicates
cannibalism
1
)
10
100
10
100
10
100
10
100
10
100
15
0
30
33.3
34
41.1
20
10.0
18
5.5
15
6.6
15
0
20
80.0
15
0
15
0
1
)
%
of
replicates
in
which
cannibalism
occurred.
TABLE
V
Survival
of
newly
hatched
larvae
of
Ph.
numidicus
cannibalizing
a
limited
number
of
eggs
(27°
C,
75%
R.H.)
(Each
trial
included
10
individuals.
In
no
case
was
second
ecdysis
completed)
No.
of
Total
Total
Total
number
Duration
eggs
D
uration
duration
of
number
of
eggs
of
1st
First
devoured
of
2nd
life
as
1st
of
eggs
devoured
by
instar
ecdysis
by
2nd
instar
and
2nd
offered
the
1st
instar
larva
completed
instar
larva
instar
larva
larva
(days)
larva
(days)
(days)
0
0
3.2
3.2
1
1
5.8
5.8
2
2
4.0
0
3.0
7.0
3
3
4.0
0
4.5
8.5
4
3-4
4.0
0-1
7.5
11.5
6
3-5
4.0
1-3
11.0
15.0
36
M.
KEHAT
when
supplied
with
an
abundant
number
of
eggs
to
develop
to
the
fourth
instar,
but
did
not
allow
them
to
pupate.
The
larval
mortality
rate
increased
with
age
probably
as
a
result
of
nutritional
deficiencies
becoming
more
critical.
On
the
other
hand,
the
developmental
rate
remained
the
same
as
on
normal
food
(Fig.
4).
These
findings
are
in
contrast
to
date
on
Coccinella
7-punctata
larvae
(KomE
1962
-
in
HoDEK's
1962
review)
which
were
shown
to
behave
similarly
as
regards
mortality
and
developmental
rate,
but
completed
development
and
pupated,
when
feeding
on
their
own
eggs.
rate
of
5
development
,
(days)
3
2
1
5
number
of
4
feeding
days
3
2
1
total
number
10
of
eggs
consumed
20
n
30
40
50
1
st
2
nd
3
rd
4
th
larval
instar
Fig.
4.
Cannibalism
of
Ph.
numidicus
larvae
on
an
abundant
number
of
eggs
(27°
C,
75%
R.H.).
(Each
trial
included
15
individuals).
Cannibalism
only
was
thus
not
enough,
and
to
complete
its
development
the
larva
had
to
feed
also
on
its
natural
prey.
Feeding
on
Parlatoria
in
the
early
larval
instars
allowed
completion
of
development
even
when
the
late
larval
instars
lived
only
by
cannibalism
on
egs.
On
the
other
hand,
when
the
larva
fed
on
eggs
in
its
early
instars
it
could
complete
its
development
only
if
it
was
later
given
Parla-
toria.
Larvae
which
had
fed
by
cannibalism
on
eggs
in
their
first
three
instars,
and
had
consumed
less
than
about
38
eggs
in
their
fourth
instar
when
later
fed
on
Parlatoria
succeeded
in
pupating,
apparently
due
to
a
sufficient
consumption
of
Par-
latoria.
If
they
ate
more
than
about
38
eggs
they
were
unable
to
pupate
even
when
offered
Parlatoria.
It
seems
that
the
larvae
had
to
consume
a
critical
number
of
Parlatoria
scales
to
allow
them
to
pupate
(Fig.
5).
The
total
number
of
eggs
consumed
by
the
fourth
instar
larva,
subsisting
in
previous
instars
either
on
its
natural
prey
or
by
way
of
cannibalism,
was
the
same
S
20
%
mortality
40
60
BO
100
FEEDING
BEHAVIOUR
OF
PREDATOR
OF
SCALE
37
II.
larval
instar
III.
<38e1
>38
e1
I
pupation
0
0
75
100
100
100
V//////////////////_
17//////////////11111
r///7/////////11.1.
1////y//////11111111111.
IIIIIMW//////////
feeding
on:F7A
own
eggs
Partatoria
see
text
Fig.
5.
Likelihood
of
Ph.
numidicus
pupating
with
the
aid
of
cannibalism.
(Each
trial
included
15
individuals).
(40-61
eggs).
This
indicates
that
the
larva's
inability
to
pupate
after
living
by
cannibalism
throughout
its
life
is
not
due
to
an
insufficient
number
of
eggs
con-
sumed
in
the
fourth
instar,
but
to
nutritional
deficiency.
Nevertheless,
increased
survival
through
feeding
on
eggs
is
in
itself
important
for
the
existence
of
the
species
(BANKS,
1956).
Feeding
rate
The
feeding
rate
was
influenced
by
the
following
factors:
Stage
of
development
The
total
number
of
scales
consumed
and
the
daily
rate
of
feeding
increased
with
age
of
larvae.
This
rise
remained
almost
unaffected
by
the
nature
of
the
food
given,
whether
nymphs
or
females
of
P.
blanchardi.
Of
the
different
larval
instars,
the
fourth
instar
was
the
most
voracious;
this
was
due
to
an
increase
in
the
daily
rate
of
consumption
and
the
number
of
feeding
days
(Table
VI).
The
larvae
did
not
feed
during
the
inactive
periods
-
shortly
before
and
after
ecdysis.
Feeding
was
required
at
every
instar,
and
no
instar
reached
the
next
stage
when
food
had
been
completely
lacking.
Sex
Female
larvae
were
more
voracious
than
male
larvae.
With
adults,
too,
the
rate
of
feeding
differed
egglaying
females
had
a
higher
daily
feeding
rate
than
non-egglaying
females,
and
the
latter
consumed
more
than
males.
Of
the
different
stages
of
the
insect
the
egglaying
female
was
the
most
voracious.
(Table
VI,
Fig.
6).
38
M.
KEHAT
TABLE
VI
The
feeding
capacity
and
duration
of
development
of
Ph.
numidicus
larvae
(27°
C,
75%
R.H.)
(In
each
stage,
12-15
individuals
were
examined)
Mean
duration
of
Average
Larval
Larval
development
number
of
sex
instar
(days)
feeding
days
First
4.0
2
Male
Second
3.1
2
Third
3.5
2
Fourth
7.6
4
Average
number
of
Parlatoria
females
consumed
daily
total
3.0
8.1
15.8
21.0
Average
number
of
Parlatoria
nymphs
consumed
daily
total
18.0
40.0
76.0
,
102.5
6.1
16.3
31.6
84.0
138.0
Total
18.2
10
36
80
152
410
678
First
4.0
2
4.0
8.0
20.0
40
Female
Second
3.2
2
9.0
18.0
46.0
92
Third
3.4
2
18.6
37.3
90.0
179
Fourth
7.7
4
24.7
99.1
129.5
518
Total
18
-
.3
10
162.4
829
number
of
scales
consumed
ED
In
c
.Ln
7-
0
_C
a
a
eL
r-
E
O
o
0
0 0
C
hry
somp
ha
tus
180
160
140
120
100
80
60
40
20
-e
A
s.
9-
UI
d
_c
n.
E
9.
males
egg
lay
ng
preovipositing
females
females
F
ig.
6.
The
included
10
daily
feeding
capacity
of
adult
Ph.
numidicus
(27°
C,
75%
R.H.).
(Each
trial
adults;
duration
of
experiments
-
10
days
with
males
and
egglaying
females,
5
days
with
preovipositing
females).
27°
C
5
number
of
feeding
4
d
ays
3
27°C
34°C
2
7
34°C
7
male
/
t/
i
7
female
rate
of
8
development
(days)
6
4
2
total
number
20
of
scales
consumed
40
60
SO
100
20
daily
number
of
scales
24
consumed
28
32
36
FEEDING
BEHAVIOUR
OF
PREDATOR
OF
SCALE
39
Food
specifity
The
total
number
of
scales
consumed
was
influenced
by
the
nature
of
the
food.
Thus
both
larvae
and
adults
of
Ph.
numidicus
devoured
5
7
times
more
Parlatoria
nymphs
than
adults.
The
total
consumption
was
also
affected
by
the
species
of
the
host
consumed.
Thus
adults
of
Ph.
numidicus
consumed
about
10
times
more
Parlatoria
females
than
Chrysomphalus
aonidum
females,
which
may
be
due
to
the
differences
in
size
or
nutritional
value
between
the
females
of
these
two
scales.
No
such
differential
consumption
was
observed
when
nymphs
of
the
two
scale
species
served
as
prey
(Table
VI,
Fig.
6).
Furthermore,
Asterole-
canium
phoenicis
females
(another
pest
of
date
palms)
were
highly
immune
to
attack
by
Ph.
numidicus
larvae
or
adults,
apparently
due
to
their
hard
scale
co-
verings,
whereas
the
nymphs
of
this
scale
were
devoured
readily.
Even
with
Parla-
toria,
the
first
instar
larvae
of
the
predator
had
some
difficulties
with
feeding
on
the
female
scales
(22%
of
these
larvae
died
before
reaching
the
next
instar),
whereas
they
readily
devoured
the
other
stages
of
the
scale.
Eggs
of
Parlatoria
or
Chrysom-
phalus,
situated
beneath
the
scales,
were
not
attacked
by
adults
of
Ph.
numidicus.
This
behaviour
permits
the
re-establishment
of
the
host
insect
and
serves
as
a
mechanism
for
maintaining
the
predator.
Temperature
The
total
feeding
capacity
was
not
affected
by
temperature,
whereas
the
average
daily
rate
of
consumption
and
the
number
of
feeding
days
were
(Fig.
7).
This
has
also
been
shown
for
Coccinella
7-punctata
(HODEK,
1957;
HUKUSIMA
&
SAKURAI,
1963
-
in
HODEK,
1967).
larval
sex
Fig.
7.
influence
of
temperature
on
the
development
and
feeding
capacity
of
the
fourth
instar
larvae
of
Ph.
numidicus
feeding
on
P.
blcutchardi
females
(75%
R.H).
(Each
trial
included
12
-
15
larvae).
40
M.
KEHAT
Scarcity
of
food
For
fourth
instar
larvae
feeding
under
conditions
of
food
scarcity,
the
overall
rate
of
development
was
lengthened,
the
number
of
feeding
days
increased,
the
mortality
rate
rose,
and
the
total
food
consumption
dropped.
Very
small
differences
in
the
extremely
suboptimal
daily
food
supply
brought
about
very
important
changes
in
mortality,
and
in
developmental
rate,
but
not
so
in
the
total
consumption
or
in
size.
On
the
other
hand,
the
enormous
differences
in
the
daily
food
supply
near
the
optimum
did
not
appreciably
change
either mortality
or
developmental
rate,
but
significantly
influenced
the
total
consumption
and
the
size
of
adults
(Fig.
8).
The
developmental
rate
of
the
pupa
was
not
influenced
at
all
by
the
changes
in
the
daily
food
supply
and
was
in
all
cases,
about
7
days.
The
minimal
amount
of
food
which
allowed
completion
of
larval
development
was
about
seven
times
less
than
the
normal
consumption
(see
Fig.
8);
this
indicates
12
11
10
0
2.0
length
of
1.9
adult(mm)
8
rate
of
development
(days)
0
0
0
0 0
0
1.8
1.7
1,6
1.5
total
number
of
scales
consumed
10
20
30
40-
50-
60
--
70
--
80
90-
100
%
mortality
2
3
4
5
15
30
daily
food
supply
(number
of
scales)
10
20
30
40
50
60
70
80
90
100
Fig.
8.
Development
and
feeding
of
fourth
instar
larvae
of
Ph.
ficimidicus
under
conditions
of
food
scarcity
(27°
C,
75%
R.1-1.),
(Each
trial
included
10
individuals.
Parlatoria
females
served
as
food
supply).
FEEDING
BEHAVIOUR
OF
PREDATOR
OF
SCALE
41
a
well
developed
tolerance
to
starvation
in
this
insect.
The
capacity
to
survive
at
very
low
host
densities
on
the
one
hand,
and
the
ability
to
destroy
large
numbers
of
host
insects
at
high
host
densities
on
the
other
hand,
are
of
primary
importance
for
the
efficiency
of
a
natural
enemy.
Fourth
instar
larvae,
under
conditions
of
food
scarcity,
developed
into
small
adults
(see
Fig.
8);
well-fed
larvae
developed
into
voracious
fourth
instar
larvae
which
required
and
were
capable
of
consuming
a
larger
number
of
scales
(Fig.
9).
d
ra
e
t
v
e
el
o
o
f
10
developme
nt
(days)
8
6
El
4
3
100
total
number
of
scales
consumed
80
60
male
female
larval
sex
D
after
food
scarcity
ag
after
food
abundance
Fig.
9.
The
effect
of
starvation
in
all
preceding
instars
on
the
development
and
feeding
rates
of
fourth
instar
larvae
of
Ph.
nurniclicus.
(Each
trial
included
10
individuals.
Purlatoria
females
served
as
food
supply.
Food
scarcity
50%
of
the
consumption
under
conditions
of
food
abundance
was
offered
to
the
predator)
This
suggests
that
the
feeding
capacity
of
larvae
at
high
host
densities
is
higher
than
at
lower
host
densities,
as
has
been
shown
in
some
other
Coccinellidae
(HODEK,
1957;
SMITH,
1965).
The
predatory
activity
is
therefore
host-density
dependent.
I
wish
to
express
my
thanks
to
all
those
who
assisted
me
with
their
advice,
especially
Professors
Z.
Avidov
and
E.
Swirski.
RESUME`
COMPORTEMENT
ALIMENTAIRE
DE
PHAROSCYMNUS
NIJMIDICUS
(COCCINEL-
L1DAE),
PREDATEUR
DE
LA
COCHENILLE
DU
PALMIER
DATTIER,
PARLATORIA
BLANCHARDI
La
capacite
de
Ph.
numidicus
de
trouver
la
proie,
determines
par
la
mobilite
et
le
degre
de
survie,
s'ameliore
avec
ragc
des
larves.
Les
mouvernents
de
recherche
sant
de
nature
aleatoire;
le
predateur
ne
possede
pas
le
pouvoir
de
percevoir
la
proie,
et
les
directions
de
son
mouvement
sont
determinees
par
des
facteurs
physiques,
comme
la
lurniere.
La
possibilite
de
se
nourrir
42
M,
KEHAT
sur
des
aliments
non-specifiques
augmente
les
chances
de
survie
clans
les
conditions
d'une
pOnurie
de
nourriture
naturelle.
De
ce
point
de
vue
le
eannibalisme
pos.sede
one
importance
particuliere
pour
la
survie.
La
capacite
de
se
nourrir
depend
du
stade,
du
sexe,
de
la
nourriture
precedente,
de
la
temperature
atmospherique
et
de
la
densite
de
population
de
l'insecte-hote.
REFERENCES
BANKS,
C.
J.
(1954).
The
searching
behaviour
of
coccinellid
larvae.
Brit.
T.
Anim.
Behay.
2
:
37-38.
—(1956).
Observations
on
the
behaviour
and
mortality
in
Coccinellidae
before
dispersal
from
the
egg
shells.
Proc.
R.
ent.
Soc.
Lond.
A.
31
:
56-60.
DIXON,
A.
F.
G.
(1959).
An
experimental
study
of
the
searching
behaviour
of
the
predatory
coccinellid
beetle
Adalia
decempunctata
L.
J.
Anim.
Ecol.
28:
259-281.
HAGEN,
K.
S.
(1962).
Biology
and
ecology
of
predaceous
Coccinellidae.
Ann.
Rev.
Ent.
7:
289-326.
HODEK,
I.
(1957).
The
larval
food
consumption
of
Coccinella
7-punctata
L.
(in
Czech.
with
English
and
Russian
Sum.).
Folia
Zool.
6
:
3-11.
(1967).
Bionomies
and
ecology
of
predaceous
Coceinellidae.
Ann.
Rev.
Ent.
12:
79-104.
IBRAHIM,
M. M.
(1955).
Studies
on
Coccinella
undecimpunctata
aegyptiaca
Rche.
TI.
Biology
and
life
history.
Bull.
Soc.
ent.
Egypte
39
:
395-423.
KADDOU,
I.
(1960).
The
feeding
behaviour
of
Hippodamia
quinquesignata
Kirby
larvae.
Univ.
Calif.
Publ.
Ent.
16
:
181-232.
KEHAT,
M.
(1966).
Ladybirds
as
predators
of
date
palm
pests.
(Doctoral
thesis,
Hebrew
Univ.
of
Jerusalem).
(1967a).
Survey
and
distribution
of
common
lady
beetles
(Coecinellidac)
in
date
palm
trees
in
Israel.
Entomophaga
12:
119-125.
(1967b).
Studies
on
the
biology
and
ecology
of
Pharoseymnus
numidicas
Pic.
(Coccinel-
lidae),
an
important
predator
of
the
date
palm
scale
Parlatoria
blanchardi
Targ.
Ann.
Soc.
ent.
Fr.
3
:
1055-1067.
%um,
B.
C.
(1965).
Differences
in
Anatis
mall
Auct.
and
Coleomegilla
maculata
lengi
Timberlake
to
changes
in
the
quality
and
quantity
of
the
larval
food.
Can.
Entomologist
97:
1157-1166.
Received
for
publication
:
1
August
1967.