Sterilization of the medterranean fruit
-6913 .
E. Truog . J . Am . Soc . Agron., 11: 8 74 - 8 8 2 ( 1 9 30 )
14 .
T. L . Yuan and J.G.A. Fiskell. Soil Sci. Soc. Amer .
Proc. ll( 3) : 202-205 (1959)
E.
STERILIZATION OF THE MEDITERRANEAN FRUIT FLY AND ITS
APPLICATION TO FLY ERADICATION
(K. P. Katiy'ar and F. Ferrer)
1.
Effect of Alternate Matings
ｾｮ
the Fertility of the
Female Medfly.
, The female of the Medfly is polygamous .
In a con-
trot program, by the sterile male technique it is very important to know the effect of two different matings (normal and
sterile) accepted by the same female on its egg fertility.
Preliminary results of multimatings of this kind were reported
last year.
The present experiment was carried out to find
out in detail the fertility of a female which first mates with
a normal male and then with an irradiated (sterile) male, or
vice versa.
The sterile males were obtained from the pupae
irradiated 24 hours before adult emergence with a dose of
10,000 r .
The f irst mating of virgin females and males was
allowed , wh e n the adults were five days old.
The eggs were
collected da ily from these females for a week and then a second mating was allowed with appropriate "kind of males.
The
females which accepted second mating were separated from those
which did not accept this mating on that day.
The females
-70which did not accept the second male on the 8th day after the
first mating were confined in cages with males throughout the
･ｾｰ･ｲｩｭ･ｮｴ｡ｬ
period of 14 days.
Eggs were collected daily
from both kinds of females s i.e s those mated twice and the
ones which were caged with males.
peated four times.
This experiment was re-
The number of females completing the first
mating varied 200-400 in different experiments.
The results
of the experiments are summarized and presented in Table 22.
It is evident from the data s that in females which
mate twice, the influence of the second mating is always
greater than the first one on the egg fertility.
The females
which were laying ·1 0 0 percent fertile eggs after the first
mating with normal males s laid on an average 43.2 percent
fertile eggs over a period of two weeks of oviposition after
they had accepted the second mating of sterile males.
Here
the second mating of sterile males had reduced the fertility
by 56.8 percent (from 100 to 43.2 percent).
Similarlys the
second mating with normal males increased the fertility by
86 . 7 percent in females which were mated previously to sterile
males .
Fe ma l e s mated first with sterile males were laying
1.8 percent fertile eggs .
The fertility increased to 88.5
percent as determined over a period of two weeks s after they
had mated with normal males.
The reason that the effect of the second mating is
more pronoun ced .t h a t
the first one on the fertility of a fe-
males is probably that the sperm requirement of such a female
is not satisfied
ｦ ｾｯｭ
the first mating.
-71 Table 22
Effect of multimaiings on the fertility of
normal Medfly ｦ ｾ ｭ ｡ ｬ ･ ｳ
Treatment
Mating sequence a)
ND
1.
Nｾ
2.
ｎ ｾ ｸ
501'
ｾ
x NO""x
I
3.
4.
5.
6•
a)
ｎ
x
ｎｾ
x
ｎｾ
I
SV'{x
No-'1 x
ｎｾｘ
I
N9x
Sot
ｾｎ
ｾ
ｓｾ
r:P
S..,X ｎ ｾ
I
Percent fertility
Expt Expt Expt
Expt
1 II
1
II
IV
Average
100 .0 1 0 0.0 1 0 0. 0 100.0
100 . 0
3.5
1.7
1. 8
0.2
1.8
69 .2
36. 0
24 •1
43.3
43.2
80.7
90 . 7
98.4
84.0
88.5
82.9
89 .9 1 0 0. 0
9 1.7
91.1
16.6
52.5
6.5
30.3
45 . 6
The letters N and S designate Normal and Sterilized
The numbers I, 2 and t:P refer
flies. respectively.
to first , second and infinite matings. respectively
The females which did not accept second mating a
week after the first mating, were confined in cages with normal or sterile males.
Their egg fertility measured over a
period of two weeks was not much influenced by the constant
presence of these males.
The presence of sterile males with
females mated first to normal males reduced the egg-hatch
o n l y by 8.9 percent (from 100 to 91.1 percent).
Similarly ,
the normal males caged with females which had mated first
with sterile males increased the egg hatch of the females by
28 .5 percent (from 1.8 to 30 . 3 percent).
It seems therefore
that the fertility of the females which had mated once does
not vary much when these females were caged constantly with
the males.
It is probably due to the fact that a greater
percent of these females do not accept more than one mating.
-72The results in Table 23 indicate the percent of
females which accepted a second mating a week after the first
mating.
It is evident from the data that not more than 16
percent of the females accept a second mating.
It seems that
the majority of the females satisfy their sperm requirement
from the first mating alone
On an average , 8 percent of the
females accept a second mating with sterile males when they
had mated first with normal males.
cent of the females
ｭｾｴ･､
A percentage of 15 .1 per-
for the second time with normal
males when they had mated previously to sterile males.
As has been pointed out previously, it was found
that the constant presence of males with females which had
mated once did not affect the fertility very much.
In these
experiments, the daily male mortality was not recorded.
It
is just possible that the majority of males died shortly
after their introduction into the cages and so the chances of
a second mating of the females by these males was reduced.
Experiment N°S was designed in which a week after the first
mating, males were introduced in larger numbers with the females and daily adult mortality was recorded.
The male mor-
tality was not very high and so enough males were always present in treatments 5 a n d 6, as s how n in Ta bl e 24 .
The results indicate that the constant presence o f
the males with the females after they had mated once, does not
change very much their egg fertility.
Presence of sterile
males with the femaled mated previously with normal males,
reduced the egg fertility only by 29.9S percent (from 104.46
-73Table 23
P e r c e n t Medfly females.accepting two matings a)
Female
Mating sequence
x
First ｾ
x
Second rY"
Normal
x
x Irradiated
Normal
"
"
"
Total N°females:
% feMated
Mated
males
on ce
twi ce a) mated
twice
II
IV
Average
285
92
18
9
6.3
9.8
8.0
I I
229
103
36
15
15.7
14 . 6
15.1
Normal x Irradiated x Normal
tI
a)
11
"
IV
Average
Second mating wa s tried a week after the first mating .
Table 24
Effect of alternate matings on the fertility
of the female Medfly
Treatment N°
Mating sequence a)
1-
2.
ｎ
ｾ
ｎｾ
N° of eggs
exam ined hatched
%
hatched
% fer tility
100 . 0
x N 00-"
1880
1496
89. 0 5
x S o-f"
760 1
262
3.45
3.87
07'
2899
2697
93.03
104.46
3.
ｎ
4.
ｎｾ
x sot'
8679
137
5 .11
6.86
5.
ｎ ｾ
x No;:' x ｳｾ
4624
3439
74 . 3 7
83.51
6.
N!?
x
4415
2017
45.68
52.29
a)
ｾ
x N
ｳｾｸ
,
N9;Z
The lettersN and S designated ｎ ｯ ｲ ｭ ｾ ｬ
and Sterilized flies,
respectively.
The numbers IJ 2 and 00
refer to first, second and infinite matings, respectively .
-74to 83 . 5 1 percent ) .
Similarly, constant presence of normal
males in a female population mated previously with sterile
males, increased the egg fertility by 45.83 percent (from
6.86 to 52.29 percent ) .
These results indicate that influence of subsequent matings by normal males after sterile matings is
almdst twice as effective (as far as fertility of the female
is concerned) as when sterile matings follow the normal ones .
2.
Effect of Humidity on Egg-hatch of the Medfly.
In experiments with the Medfly, we have .b e e n using
three different oviposition materials (Fig. 16) :
cial plastic lemon molds;
( 1 ) artifi-
(2) artificial orange molds; and
(3) quart-size polyethylene round freezer jars.
In the plas-
tic lemons and oranges, a circular hole of approximately 1"
diameter was cut at the anterior end, to plug in a rubber
stopper which works as a support to hold the molds vertically
inside the cages during oviposition.
The freezer jars
are put vertically in the cages, tightened with bakelite
screw caps.
Numerous holes a re punctured in the lemons, or-
anges and freezer jars with a needle to facilitate penetration of the female ovipositor for egg laying inside these
devices .
The oranges, lemons and freezer jars are rinsed with
tap water before putting in the cages for oviposition.
The standard practice used in our laboratory to
､･ｴ ｲｭｩｾＬ
the egg -hatch is to leave the oviposition
ｭ｡ｾ･ｲｩ｡ｬ
Fig. 16.
Plastic lemon and orang. molds and polyethylene
freezer jars used for the Medfly oviposition.
-76in the cage with th e flies for 24 hours .
The eggs are then
washed out and incubated on moist filter paper in petri
dishes for 48 hours at room temperature (about 25°C) to determine the egg-hatch.
In past experiments, we used lemon
and orange molds for oviposition and the egg-hatch was recorded low and very erratic.
On the other hand, the use of
polyethylene jars always gave high and constant egg-hatch.
It was suspected that low egg-hatch with the use
of lemons and oranges as oviposition medium was due to low
ｾｵｭｩ､ ｴｹ
inside these molds during the oviposition period ,
rather than any toxic effect of the plastic itself on the
eggs.
A series of experiments was conducted to determine
the adverse effect of low humidities on the egg-hatch of the
Medfly.
Tables
The results of these experiments are presented in
25, 26, 27, 28 , 29 and 30.
In the first experiment, two sets of oviposition
devices were tried.
One set consisted of plastic jars, lemons
and oranges r insed with tap water and the
and oranges.
ｾｴｨ･ｲ
of dry lemons
The oviposition was allowed for 24 hours.
The
eggs were then washed out and incubated on moist filter paper
unt il hatched (for 48 hours).
daily for a week.
in Table 25.
The egg collections were made
The results of this experiment are given
The data indicate clearly that moistened or-
anges and lemons gave a higher percent egg-hatch than dry ones.
The rinsed plastic jars gave the best egg-hatch (87 .4 percent) .
-77Table 25
ｅｦｾｴ
of various kinds of oviposition devices
on the egg-hatch of the Medfly
Ovipisition devices
Total N°of
eggs examined
%
hatched a)
Moist plastic jars
Moist plastic oranges
Moist plastic lemons
7941
7282
7706
87.4
45.2
Dry plastic oranges
Dry plastic lemons
6264
5817
17. 0
14.8
a)
31 • 7
Average of four replications .
The water rinsed oranges and lemons did not give as high a
percentage egg-hatch as the water rinsed plastic jars.
This
is probably due to the dry atmosphere inside the oranges and
lemons.
After rinsing , the water did not stay inside the
lemons and oranges, but instead dripped down through the openi n g t hrou g h which th e ru b b er stoppe r s we re plu g ged . as th e
stoppers were not water tight.
In the plastic jars after
rinsing, the water adhering to the inside surface of t h e
jars dripped down and collected in the bottom of the jars
in the bakelite caps.
This water supplied a very high hum-
idity inside the jars throught the oviposition period of
24 hours .
In order to prove that low egg-hatch in 'wa t e r rinsed
lemons and oranges was due to lack of water retention inside
these molds,
the second experiment was conducted in which 3-4 ml
-78of water was placed in small plastic containers glued over the
top of the rubber stoppers.
Oranges and lemon. with such de-
vices were called humid oranges and lemons.
The results of
this experiment are presented in Table 26.
It is evident
from these data that the humid oranges and lemons with water
inside gave high egg-hatch respectively -
78.0 percent and 86.6 percent,
close to the percentage of egg-hatch in moist
plastic jars (91.1 percent), while the egg-hatch in the water
rinsed oranges and lemons was 57 .1 and 70.8 percent , respectively.
Table 26
Effect of humidity inside ovip osition devices
on the egg-hatch of the Medfly
Oviposition devices
Moist plastic jar
Moist plastic orange
Moist plastic lemon
Dry plastic orange
Dry plastic lemon
Humid plastic orange*
Humid plastic lemon*
*
Total N°of
eggs examined
%
hatched
1777
820
1063
91. 1
851
530
32.1
2 7.2
1122
125 7
78. 0
86.6
57 .1
70.8
A small amount (3-4 ml) of water was put in plastic receptacles inside the orange and lemon molds, and glued over
the rubber stoppers.
In order to further prove that the low percent 'egg-hatch
in water rinsed plastic lemons and oranges
ｷ｡ｳｭｾｲ･ｬｹ
due to
low humidity inside them, rather than any possible toxic effect
of the plast ic on the eggs , the third experiment was carried out.
-79.In this experiment, water r i n s e d lemons and o ran ges were
used f or oviposition.
Egg laying wa.s allowed for one hour.
The lemons and oranges were removed at the end of the ovipaot ion, and were stored under two .d i f f e r e n t
cond itions.
One
group was s tored at room humidity (50-60 percent) and the
othe r one at 100 percent humidity ( inside a desiccator containing distilled water) .
From each group, the eggs were
washed out at an interval of every two hours, until 24 hours ,
and p laced on moist filter paper in petri dishes to examine
the egg-hatch .
The results of this experiment are summarized
and presented in Table 27 .
Table 27
Eff ect o f humidity during incubation period
on the egg-hatch of the Medfly
Period
of
incubation
0
2
4
6
8
10
12
14
16
18
20
22
24
*
hr
hrs
hrs
hrs
hrs
hrs
hrs
h rs
hrs
hra
hrs
hr
s
hrs
Average percent of egg-hatch
100% humidity
ａｾｭｯｳｰｨ･ｲｩ｣
humidity*
oranges
lemons
lemons
oranzes
9 4 .7
9 4.3
94.5
9 1. 9
78.4
88.2
54.7
4 0. 1
35.5
7.8
6.3
2. 4
2.0
50-60 percent .
93 . 0
86.1
91.3
90.6
78.9
83.8
81.5
32.6
21.3
3 .2
1. 7
0.5
0.0
87.7
90.4
8 4.7
93.7
94.3
86.6
94 . 3
95 .0
94 . 5
9 1.6
95 .6
96 .7
87 .9
88 .9
91.9
92. 1
96 .0
85 .3
88.3
90 .5
94.5
94 . 7
90 . 5
95.1
88.0
91.8
-80The results clearly indicate that lower egg-hatch
in rinsed lemons and oranges is merely due to low humidity
inside them.
The oranges and lemons stored at 100 percent
humidity gave normal
･ｧ ｾｨ｡ｴ｣ｨ
to incubation of 24 hours.
(84.7-96.7 percent) even up
Those stored at room humidity
however, gave normal egg-hatch up to 10 hours of incubation .
After this period, the percent of egg-hatch was
lowered (54.7-0.0 percent).
｣ｯｾｳｩ､･ｲ｡｢ｬｹ
The results of this experiment
indicate that whenever we are forced to use plastic lemons
or oranges as oviposition medium, due to use of small sized
cages, we must wash out the eggs before 10 hours after oviposition.
Experiment 4, as shown in Table 28 , was carried out
to determine the maximum period of egg incubation in our
laboratory (at atmospheric humidity of 50 -60 percent) without lowering the percent egg-hatch.
In this experiment, the
oviposition was allowed for one hour in dry plastic jars.
The eggs were shaken off dry from these jars and incubated
0-24 hours in dry petri dishes.
The eggs were moistened
every two hours for 24 hours and put on damp filter paper
to determine the percentage hatched.
The results in Table 28 indicate that under our
laboraiory conditions of 25°C temperature and 50-60 percent
humidity, eggs can stay normal up to 8 hours without lowering
hatchability .
The results of this and the previous experiment
(Table 27) indicate that under our laboratory conditions, oviposition should not be allowed beyond 8-10 hours in plastic
- 81 lemons and o ranges.
Ovipos i t io n periods longer than 8-10
hours reduced the percent egg-hatch due to desiccation of
t h e eggs i n si d e the ovipos i t ion med ium .
Table 28
Effect o f room humidity dur ing incubation
on the egg-hatch of the Medfly
Incubation
period*
Expt I
Percent of egg-hatch
Expt II
Average
0
2
4
6
8
10
12
14
16
18
20
22
24
hI'
hrs
hra
hrs
hrs
hrs
hI'S
hrs
hrs
hI'S
hI's
*
Eggs were incubated for the desired length of periods at
atmospheric humidity of 50-60 .percent, before putting on
moist ｦ ｩ ｬ ｴ ･ ｾ
paper until hatched.
81. 0
87.3
84.9
90.9
80.1
47.5
5.6
6. 6
0.0
hI'S
hI'S
0.0
91.5
90.8
96.2
94.8
9.4.4
34.9
19.6
8.8
4 .1
3.5
86.3
89 .0
90.6
92.8
87 .2
41.2
12.6
8.8
5.4
3.5
2.8
2 .9
0.7
1. 4
0 .3
1. 4
It has been found that i n an incubation of eggs at
atmospheri c hum idity of 50 -60 percent, normal hatch occurs
only up to 8 hours (Table 28).
In the next experiment, effect
of incubation of eggs for 24 hours at five different high humidities was stud ied on the egg-hatch.
The humidities of 75.5,
85.0. 92 .5, 97,5 and 100 percents were created in desiccators
by saturated salt solutions of sodium chloride. potassium
-82chloride . potassium nitrate . potassium sulfate and distilled
water , respectively .
Eggs laid in d ry plastic jars were put in open dry
petri dishes inside the desiccators.
cubation at the different humidities
After 24 hours of int
ｴｨ･
ﾷ ｾ Ｎ･ｧｳ
were moistened
and transferred to wet filter paper for further incubation
for 48 hours to determine the percent hatched.
ment was repeated five times.
The experi-
The results of these experi'\
me nts a re s ummarized in Table 29.
The results indicate that the normal egg-hatch
( 9 3 . 0 percent) occurred from 100 to 92.5 percent humidity.
At 85 .0 percent humidity, only 1.8 percent eggs -hatched, and
none were recorded at the 75.5 percent h umi di t y le vel.
Tabl e 29
Effect of various humidities during Ln c ub at ion '* on
egg-hatch of the Medfly
Percent
humidities
Expt
I
ｅｾｩｴ
check
100.0
97 . 5
9 2. 5
\8 5 . 0
ＷＵ
Ｌｾ 5
93.3
95.5
87.9
95.2
3. 9
0 .0
85 .6
77 .6
77.6
86 .0
2 .6
0.0
'*
!
Percent of egg-hatch
Expt
Expt
Expt
V
III
IV
For a period of 24 ho u rs . ,
95.3
94.6
93.4
90.2
0.6
0.0
95.1
94.2
9 3 .2
93.9
1 •a
0.0
93.2
96.5
96 . 1
9 4 .9
0.7
0.0
Average
92.5
91. 7
89.6
93 .0
1. 8
0 .0
-83:Th e incubation of eggs for 24 hOUTS at 85 and 75.5
percent
ｨｾｭｩ､ ｴｩ･ｳ
is fatal for the Medfly eggs.
The next
experiment was designed to study the maximum incubation for
Medfly eggs at these humidities without lowering the percent
of egg-hatch .
in Table 30.
The results of this experiment are presented
It is evident from the data that incubation of
eggs at 75.5 and 85 percent humidities has no adverse effect
on its hatch up to 8 and 12 hours, respectively.
Table 3 0
Effect of incubat ion of Medfly eggs in low
humidities for va rious ' l e n g t h s of time on hatchability
Length
of incubation
Percent of egg-hatch
75 percent humidity
85 percent humidity
Expt
Expt
AverExpt
Expt
AverII
I
II
I
age
age
2 hr s
4 hra
6 hra
8 hr s
10 hrs
12 hrs
14 h r s
16 hrs
1 8 hrs
20 hrs
22 hrs
24 hrs
93.8
89.0
89.0
93 .9
84.9
90 . 7
75. 3
750 3
87 .0
80.0
56 .3
59.5
96 . 6
92.2
92. 1
87.4
8 1.8
90 .3
86.3
84 . 3
89.2
75.0
76.6
65 .0
95.2
90.6
90.6
90.6
83.4
90.5
80.8
79 .8
88 .1
77 . 5
66 .4
62.2
92. 9
85.1
85.9
84 . 5
69.3
53. 7
36. 1
23.3
20.2
10 .5
0.8
2 .2
95 .7
90 .4
88.8
88 .3
71.4
63 .3
33.2
26 .7
1 2. 3
1 0 03
4.4
2.6
94.3
87.8
87.4
86.4
70.4
58.5
34 .6
25.0
16 .2
10 .4
206
2 .4
The resul ts of all these experiments (Tables 25 , 26 ,
2 7 , 2 8 , 2 9 an d 30 ) in dic at e th at in Med f l y ex pe ri ment s un d er
our laboratory conditions (25°C and 50-60 percent humidity)
whenever wa ter
｣ｾｮ ｯｴ
be maintained consistently inside the
ov iposition medium, the eggs must be washed out within 8 hours
-84of oviposition.
A period longer than 8 hours will lower
ｆｯｲｴｵｮ｡ｴ･ｬｹｾ
the hatchability due to desiccation of the eggs.
with the use of plast ic freezer . jars as oviposition medium,
the problem of egg desiccation does not arise.
When the jars
are rinsed with tap water, a good amount of it collects down
in the bo ttom of the jars in the bakelite screw caps.
This
water keeps the atmosphere inside the jars saturated with
humidity during the oviposition period .
3.
Evaluation of the Performance of Four Different
Types of Yeasts in the Larval Diet of the Medfly.
The insect control or eradication program by the
sterile male technique needs rearing of the adults in the
laboratory in large quantities for field release.
In our
coope rat ive project with OIRSA on the Medfly problem in Central America, the flies are being reared in the laboratory
in mil lions for ir radiation and later release in , the field.
The larval food is the most expensive item beside the labor
and equipment in Medfly rearing.
The standard formula for
the la rval diet consists of:
Dry c a r r ot p owder
Dry brewer's yeast powde r
Sodium benzoate (to inhibit molds)
Cone. HCI ( to bring pH 4 to 4.5)
Tap wate r
The ma jor cost i n l a r v a l
powder and the yeast.
100 gm
25
1-2
4-6 ml
500-600
food comes from the carrot
Sodium benzoate and hydrochloric acid
const itute o n l y a v e r y small fr a c ti o n of the total food cost .
-85Currently we are u.ing Fleischman 's pure primary-grown dry
yeast type 300-B. obtained from Standard Brands, at a price
of $0 . 6 2 per lb.
In the present experiment , Fleischman 's pure primary-grown dry yeast type 2019, Fleischman's yeast ' extract
type 3 and Lake States dried torula yeast USP XV type CF
(F) ｷ ｾ ｲ
tried in the larval ｾ ｩ ･ ｴ
' t o rear the Medfly.
2
The
objective was to find out some cheap yeast which wili better
or equal the performance of the currently used type 300-B.
Type 2019
ｩｾ
the cheapest yeast ($0 . 4 1 per lb, plus freight)
produced by Standard Brands.
Torula is produced by Lake
States yeast and chemical division of the St. Regis Paper Co .
in Wisconsin.
Its price is $0.21 per lb, plus freight.
Yeast
extract type 3 is also a Standard Brands product and costs
$2.48 per lb, plus freight.
The reason for the inclusion of
yeast extract type 3. although so much more expensive, was
to see if it would give a higher percent pupal yield from the
larval medium as compared to the other types .
Larval diet was prepared according to the formula
given prev iously.
Three thousand eggs were put on about
350 ml of this diet, i.e., at the rate of 9000 eggs per liter
of larval medium.
Each treatment was replicated six times.
The data were taken on average weight per pupa, total number of pupae recovered , percent adult emergence from the
pupae, egg fertility and fecundity of females and the longevity of the adults.
The rearing was carried up to the
-86second generation.
The results of these experiments are
summarized and presented in Tables 31, 32, 33 , 34, 35, 36,
37 and 38.
Average weights per pupa of all the treatments for
the two generations are presented in Table 31.
The data in-
dicate that so far as pupal weight is concerned, there is
no difference up to the second generation in any treatment.
Pupae from all the yeasts weighed on an average , 8 mg per
pupa.
ｔｨ
ｾ
results on the effect of the different types
of yeast used in the larval diet on the total pupal recovery
are presented in Table 32.
The , data indicate that except
for type 3, all yeasts gave more than 50 percent pupal recovery .
Ta b l e 31
Effect of different types of yeasts given in the larval diet for
two successive generations on the weight a) of the Medfly pupae
Types
of
yeast
Torula
Genera tion
Av wt of each pupa b ) in mg .
Rep
Rep
Rep
Rep
Rep
Rep
I
II
III
IV
V
Average
VI
8.43
7. 9 1
8 .33
8 .22
7.0 4
8 .00
8.27
II
7. 9 3
7.85
8.7 1
8.18
8 .30
8 .02
8.20
I
II
7 .72
8 .09
8.63
8 .08
8.08
8.26
8.00
8.73
7 . 70
8.09
7. 98
7.90
8.04
8.17
20 19
I
II
7 . 22
8.08
7.38
7.85
7. 6 8
7.82
7.58
7 . 82
7.69
8.77
7.88
8.67
7.57
8.17
Type 3
I
II
7.98
8.11
8 .17
8.26
8 .02
7.97
7. 91
8.01
8.39
8.10
8 .19
8.07
8 .04
300 -B
a)
b)
I
7. 5 9
Based on pupal age of 48 hours.
Based on average weights of 100 pupae
-87Table 32
Effect of different yeasts given in the larval diet for two
successive generations on the pupal recovery of the Medfly
Types
of
yeast
N° of pupae recovered from each
Generatian
Rep
I
Torula
I
II
tray of larval medium a)
Rep
Rep
Rep
Rep
V
Rep
I
II
VI
I
II
IV
1322
2276
1453
2553
1747
2159
1806
2394
1 7 25
1378
1600
1512
1609
2029
1819
64
70
2159
12 76
1655
933
1688
933
1629
933
1982
806
21 0 0
11 0 6
1869
998
1434
74
34
2 162
1276
1924
1100
1688
1544
1629
1570
2287
1 9 89
1982
176 7
1945
1541
1783
77
53
1100
1512
10 4 1
1394
500
629
806
688
924
283
924
417
882
821
852
Av
Type 3
I
II
Av
a)
%
pupal
recovery
III
Av
2019
of
pupae
II
Av
300-B
Av N°
35
28
Each t ray contained 1/3 liter of larval medium on which
3000 eggs were applied .
The low (34 percent) pupal recovery in the second generation
with type 300-B is due to fungus growth in the larval medium
in its four replicates.
The average pupal yield per liter
of larval medium for the two generations in torula, type 2019,
type 300-B and type 3, is 5457, 5349, 4302 and 2556 pupae,
respectively .
These data indicate
｣ｬ･｡ｾｬｹ
that either torula
or type 2019 can be used effectively in place of the currently
used type 300=B for Medfly r e a ri n g , without lowering the
pupal recovery from the larval medium.
-88The adult emergence from the pupae is fairly high
(73-96 percent) in all the treatments (Table
Ｓｾ
Ｎ
No adverse
effect was noticed on adult emergence from any yeast tested
in the experiments.
Table 33
Effect of various yeasts in larval diet on the adult emergence
of the MedflYt tested for two successive generations
Percent adult .erne rgence a)
1st generation
2nd generation
Types of yeast
Torula
91.8
96.0
300-B
91. 7
76.8
20 19
88.8
72. 6
Type 3
94.3
87.8
a)
Based on six replicates .
100 pupae.
Each replicate consisted of
Table 34
Effect of various yeasts in larval diet on the egg fertility
of adult Medflies tested for two successive generations.
Types of
yeast
1st generation
Total N° of
%
eggs exam- hatched
ined
2nd generation
%
Total N°of
eggs exam- hatched
ined
Torula
13481
9 1.0
13986
92.0
300-B
12 4 14
93 . 0
758 7
92 . 0
2019
13705
94 . 2
10418
83 .6
Type 3
12050
9 1. 1
11722
93.7
-89 S imil arly , th e pe r cen tage of egg -hat c h was v e r y
high (84-94 percent ) in al l
the treatments (Table 34).
Thus
fert ility of the ad ults i s not r e d u c e d by the use of any of
t h e yeasts tested.
Data on the daily adult mortality were recorded
fo r each sex.
The ave rage numbe r of females l iving in a
particular week was calculated from the number of females
a li ve on the first and last day of that week .
Th is average
n umber of females per week was used later to calculate the
average number of eggs produced per female per week.
da ily egg production was recorded volumetrically for
treatment.
The
･｡ｾｨ
The number of eggs was calculated on the basis
of 0.01 ml equal t o 330 eggs .
The egg colle c t i o n wa s s ta rted
when the flies were one week old, and was contin ued for four
weeks.
The average number of eggs produced per female per
week for the different treatments is summarized i n Tab les 35
and 36 for the first and second generations, respectively .
The results shown in Table 35 indicate that in the
firs t
ge ne ra t ion , t or ula a n d t ype 300-B ga ve on a n a v e ra g e
70 0 eggs, while type 2019 and type-3 gave 800 eggs pe r female
dur ing thei r fou r weeks of ovipos i tion.
In the second gener -
a t ion, ex cept for type 300-B, all treatments yie lded 600 eggs
per female d ur ing the fo u r weeks of ov iposition .
egg-y ield (202)
The l ow
i n the case of 300-B was not real, as this i s
the s tandard yeast used in our laboratory for the last five
years fo r the rearing of th e Medfl y .
-90Table 35
Effect of different types of yeast given in the larval diet
on the fecundity of adult Medfly females of the first generation
NG of eggs laid per female*per week during
Treatments
1st
week
Torula
300 -B
'2 0 1 9
Type 3
*
different weeks of oviposition
4th
2nd
3rd
week
week
week
Total
Rep
I
Rep II
Average
196
154
176
185
310
248
129
249
189
88
85
87
700
Rep
I
Rep II
Average
136
194
166
212
255
234
168
188
178
103
130
117
695
Rep
I
Rep II
Average
237
202
220
285
306
296
149
232
191
120
97
109
816
Rep
I
Rep II
Average
126
124
125
3 19
305
312
225
250
238
88
1 74
131
B06
Based on 107-127 females laying eggs in the first week, and
30 -89 females laying eggs in the fourth week of oviposition .
The results of Tables 35 and 36 also indicate that
Medfly females lay the largest number of eggs in the second
week of oviposition.
It can be concluded from these results
that the females from the larvae reared on torula or type
20 19 produce at least an equal number of eggs as produced by
the females from type 300-B, if not more.
Thus, these pro-
ducts could be substituted successfully for the type 300-B
without lowering the egg production capacity of the females.
The adult mortality recorded daily for each sex
is summarized in Tables 37 and 38 for the first and second
generation of fl ies, rrspect ively.
The data indicate no
-91 Table 36
Effect of different types of yeast g iven in the larval diet
on t h e fecundity of the adult Medfly " females of the second generation
Treatments
1st
week
Torula
30 0-B
2 0 19
Type 3
*
eggs laid per female* per week in
different periods of oviposition
2nd
3rd
4th
week
week
week
Total
Rep I
Rep I I
Average
168
128
148
205
215
210
14 9
136
143
148
89
124
Rep
I
Rep I I
Average
65
80
73
82
101
92
21
11
40
o
31
6
202
Rep
I
Rep II
Average
199
129
164
274
190
232
145
148
147
51
82
67
610
Rep
I
Rep II
Average
154
143
250
199
225
135
132
134
70
82
76
584
149
6 25
Based on 45-93 females laying eggs in the first week and
4-19 females laying eggs in the fourth week .
noticeab le adverse effect on the longevity of the adults in
any treatment.
The flies coming from the larvae reared on
tor u la, type 2019 or type 3 live as long as those reared on
type 300=B.
As a general rule, the males die more
than fema les in all the treatments.
ｾ｡ｰｩ､
ｬｹ
In type 2019, in the
f irs t gene ration, the female mortality i s c o n s i d e r a b l y l o we r
than in any other treatment, but this trend is not noticed
in the second generation flies.
From the results of this series of experiments , it
is concluded that either torula or type 20 19 can be used
-92satisfactorily for Medfly rearing .
Use of any of these yeasts
did not affect adversely the weight of the individual pupa,
percent of pupal recovery from the larval medium, adult emergence from the pupae, fertility of the females,
the egg-laying
capacity of the females, and the longevity of the adults.
The type 3 yeast tested in these experiments is unsuitable
for mass rearing of this fly, ·primarily because of its expense
as compared to torula or type 2019.
pupal recovery from the
ｬ｡ｲｶ｡ｬｾ･､ｩｵｭ
Secondly, the percent
is low with this yeast .
Thirdly, larval and pupal period is prolonged by two days at
each stage, when type 3 is used .in the larval food.
At present, type 30Q-B is being used by the OIRSA
laboratory for mass rearing of the Medfly .
The use of torula
yeast ($0.21 per lb) in place of type 300-B ($0 . 6 2 per lb) in
the larval food, will
ｲ･ｳｵｬｾｩｮ
a 66 percent saving in yeast
cost for the Medfly rearing .
Production of one million pupae requires about
$25 of the 300-B yeast type.
yeast is about $9. 00 .
However, the cost of torula
Thus, the use of torula yeast will save
about $16 per million pupal production.
producing about 20 million pupae a month.
At present, OIRSA is
At this rate of
fly production, the use of torula will give a saving of about
$3200 per year.
-93Table 37
Effect of va rious yeasts given in larval d iet on the longevity
of the adult Medfly of the first generation ·
Treatment
Sex
Torula
0--+
Sf
30 0- B
ｾ
2019
!f
•
ｾ
Type 3
t»
f}
*
% accumulated mortality· at successive weeks
2nd
3rd
1st
4th
5th
week
week
week
week
week
14.0
4.6
40.5
9.9
74.9
32.6
51.1
100 . 0
97 . 1
11. 7
3.3
28.9
11. B
78 .7
58.2
95 . 0
64.2
100 . 0
8 3.4
20 . 1
2. 5
58.0
4.6
89.7
17.1
97.3
29.6
1 00 . 0
50 .0
8.9
4.5
29.5
11. 0
74.3
34.6
93.8
56.8
98 .5
66.2
Average of tw o replicates.
12 5.-150 fl ies .
95.5
Each replicate c onsist ed o f
Table 38
Eff e ct of vari ous y e asts given in the larval diet on the longevity of th e adult Medfly of the second generation
Treatment
Torula
300 -B
20 19
Type 3
*
Sex
ｾ
ｾ
ｾ
ｾ
0-7
ｾ
9ｾ
% accumulated mortality· at , successive weeks
3rd
1st
2nd
4th
5th
week
week
week
week
week
11.5
7.7
60 . 5
15.2
88.8
45 . 5
99 . 5
72 .2
99 .5
84.8
12.7
6.8
44.8
16.6
83.3
57.8
96.5
83.9
99. 4
93.4
20. 1
10.8
46.9
24. 0
85.2
62.3
99.3
85. 8
100 . 0
94 . 8
5 .3
4.6
35.6
14.6
84.9
42.4
96.9
72.1 '.
Based on two replications.
100 flies
99. 5
88 .3
Each replicate consisted of
-944.
A Note on the Progress of the Cooperative Project
with OIRSA .on the Medfly.
According to our agreement with OIRSA in the Medf l y project. we have furnished all the basic information
needed for the field releases (e.g., sterilization dose ,
overflooding ratio, etc.).
OIRSA has been carrying out
large scale field tests since 1963.
In th e P un t a re n a s t e s t,
the initial fruit infestation was 85 percent in September
1963.
In September 1964, a year after the sterile male re-
leases, the infestation in the same area had dropped to
three percent (as reported by OIRSA)
OIRSA previously had a grant from AID for the initiation of the Medfly project.
Recently . they have received
a new grant from the International Atomic Energy AGency to
continue this program in Central America.
The release of
sterile flies will now be extended to Nicaragua and Panama .
As we have fulfilled our agreement with OIRSA, the
laboratory wo rk on the Medfly will be gradually phased out
unless other basic information will be required by OIRSA.
The cobalt-60 source in o ur laboratory is being used by the
OIRSA l a b o r at o r y rather extens ively, and they will keep on
using th is fac ility.
It is est imated that about 4 million
pupae are irradiated weekly .
E. Truog . J . Am . Soc . Agron., 11: 8 74 - 8 8 2 ( 1 9 30 )
14 .
T. L . Yuan and J.G.A. Fiskell. Soil Sci. Soc. Amer .
Proc. ll( 3) : 202-205 (1959)
E.
STERILIZATION OF THE MEDITERRANEAN FRUIT FLY AND ITS
APPLICATION TO FLY ERADICATION
(K. P. Katiy'ar and F. Ferrer)
1.
Effect of Alternate Matings
ｾｮ
the Fertility of the
Female Medfly.
, The female of the Medfly is polygamous .
In a con-
trot program, by the sterile male technique it is very important to know the effect of two different matings (normal and
sterile) accepted by the same female on its egg fertility.
Preliminary results of multimatings of this kind were reported
last year.
The present experiment was carried out to find
out in detail the fertility of a female which first mates with
a normal male and then with an irradiated (sterile) male, or
vice versa.
The sterile males were obtained from the pupae
irradiated 24 hours before adult emergence with a dose of
10,000 r .
The f irst mating of virgin females and males was
allowed , wh e n the adults were five days old.
The eggs were
collected da ily from these females for a week and then a second mating was allowed with appropriate "kind of males.
The
females which accepted second mating were separated from those
which did not accept this mating on that day.
The females
-70which did not accept the second male on the 8th day after the
first mating were confined in cages with males throughout the
･ｾｰ･ｲｩｭ･ｮｴ｡ｬ
period of 14 days.
Eggs were collected daily
from both kinds of females s i.e s those mated twice and the
ones which were caged with males.
peated four times.
This experiment was re-
The number of females completing the first
mating varied 200-400 in different experiments.
The results
of the experiments are summarized and presented in Table 22.
It is evident from the data s that in females which
mate twice, the influence of the second mating is always
greater than the first one on the egg fertility.
The females
which were laying ·1 0 0 percent fertile eggs after the first
mating with normal males s laid on an average 43.2 percent
fertile eggs over a period of two weeks of oviposition after
they had accepted the second mating of sterile males.
Here
the second mating of sterile males had reduced the fertility
by 56.8 percent (from 100 to 43.2 percent).
Similarlys the
second mating with normal males increased the fertility by
86 . 7 percent in females which were mated previously to sterile
males .
Fe ma l e s mated first with sterile males were laying
1.8 percent fertile eggs .
The fertility increased to 88.5
percent as determined over a period of two weeks s after they
had mated with normal males.
The reason that the effect of the second mating is
more pronoun ced .t h a t
the first one on the fertility of a fe-
males is probably that the sperm requirement of such a female
is not satisfied
ｦ ｾｯｭ
the first mating.
-71 Table 22
Effect of multimaiings on the fertility of
normal Medfly ｦ ｾ ｭ ｡ ｬ ･ ｳ
Treatment
Mating sequence a)
ND
1.
Nｾ
2.
ｎ ｾ ｸ
501'
ｾ
x NO""x
I
3.
4.
5.
6•
a)
ｎ
x
ｎｾ
x
ｎｾ
I
SV'{x
No-'1 x
ｎｾｘ
I
N9x
Sot
ｾｎ
ｾ
ｓｾ
r:P
S..,X ｎ ｾ
I
Percent fertility
Expt Expt Expt
Expt
1 II
1
II
IV
Average
100 .0 1 0 0.0 1 0 0. 0 100.0
100 . 0
3.5
1.7
1. 8
0.2
1.8
69 .2
36. 0
24 •1
43.3
43.2
80.7
90 . 7
98.4
84.0
88.5
82.9
89 .9 1 0 0. 0
9 1.7
91.1
16.6
52.5
6.5
30.3
45 . 6
The letters N and S designate Normal and Sterilized
The numbers I, 2 and t:P refer
flies. respectively.
to first , second and infinite matings. respectively
The females which did not accept second mating a
week after the first mating, were confined in cages with normal or sterile males.
Their egg fertility measured over a
period of two weeks was not much influenced by the constant
presence of these males.
The presence of sterile males with
females mated first to normal males reduced the egg-hatch
o n l y by 8.9 percent (from 100 to 91.1 percent).
Similarly ,
the normal males caged with females which had mated first
with sterile males increased the egg hatch of the females by
28 .5 percent (from 1.8 to 30 . 3 percent).
It seems therefore
that the fertility of the females which had mated once does
not vary much when these females were caged constantly with
the males.
It is probably due to the fact that a greater
percent of these females do not accept more than one mating.
-72The results in Table 23 indicate the percent of
females which accepted a second mating a week after the first
mating.
It is evident from the data that not more than 16
percent of the females accept a second mating.
It seems that
the majority of the females satisfy their sperm requirement
from the first mating alone
On an average , 8 percent of the
females accept a second mating with sterile males when they
had mated first with normal males.
cent of the females
ｭｾｴ･､
A percentage of 15 .1 per-
for the second time with normal
males when they had mated previously to sterile males.
As has been pointed out previously, it was found
that the constant presence of males with females which had
mated once did not affect the fertility very much.
In these
experiments, the daily male mortality was not recorded.
It
is just possible that the majority of males died shortly
after their introduction into the cages and so the chances of
a second mating of the females by these males was reduced.
Experiment N°S was designed in which a week after the first
mating, males were introduced in larger numbers with the females and daily adult mortality was recorded.
The male mor-
tality was not very high and so enough males were always present in treatments 5 a n d 6, as s how n in Ta bl e 24 .
The results indicate that the constant presence o f
the males with the females after they had mated once, does not
change very much their egg fertility.
Presence of sterile
males with the femaled mated previously with normal males,
reduced the egg fertility only by 29.9S percent (from 104.46
-73Table 23
P e r c e n t Medfly females.accepting two matings a)
Female
Mating sequence
x
First ｾ
x
Second rY"
Normal
x
x Irradiated
Normal
"
"
"
Total N°females:
% feMated
Mated
males
on ce
twi ce a) mated
twice
II
IV
Average
285
92
18
9
6.3
9.8
8.0
I I
229
103
36
15
15.7
14 . 6
15.1
Normal x Irradiated x Normal
tI
a)
11
"
IV
Average
Second mating wa s tried a week after the first mating .
Table 24
Effect of alternate matings on the fertility
of the female Medfly
Treatment N°
Mating sequence a)
1-
2.
ｎ
ｾ
ｎｾ
N° of eggs
exam ined hatched
%
hatched
% fer tility
100 . 0
x N 00-"
1880
1496
89. 0 5
x S o-f"
760 1
262
3.45
3.87
07'
2899
2697
93.03
104.46
3.
ｎ
4.
ｎｾ
x sot'
8679
137
5 .11
6.86
5.
ｎ ｾ
x No;:' x ｳｾ
4624
3439
74 . 3 7
83.51
6.
N!?
x
4415
2017
45.68
52.29
a)
ｾ
x N
ｳｾｸ
,
N9;Z
The lettersN and S designated ｎ ｯ ｲ ｭ ｾ ｬ
and Sterilized flies,
respectively.
The numbers IJ 2 and 00
refer to first, second and infinite matings, respectively .
-74to 83 . 5 1 percent ) .
Similarly, constant presence of normal
males in a female population mated previously with sterile
males, increased the egg fertility by 45.83 percent (from
6.86 to 52.29 percent ) .
These results indicate that influence of subsequent matings by normal males after sterile matings is
almdst twice as effective (as far as fertility of the female
is concerned) as when sterile matings follow the normal ones .
2.
Effect of Humidity on Egg-hatch of the Medfly.
In experiments with the Medfly, we have .b e e n using
three different oviposition materials (Fig. 16) :
cial plastic lemon molds;
( 1 ) artifi-
(2) artificial orange molds; and
(3) quart-size polyethylene round freezer jars.
In the plas-
tic lemons and oranges, a circular hole of approximately 1"
diameter was cut at the anterior end, to plug in a rubber
stopper which works as a support to hold the molds vertically
inside the cages during oviposition.
The freezer jars
are put vertically in the cages, tightened with bakelite
screw caps.
Numerous holes a re punctured in the lemons, or-
anges and freezer jars with a needle to facilitate penetration of the female ovipositor for egg laying inside these
devices .
The oranges, lemons and freezer jars are rinsed with
tap water before putting in the cages for oviposition.
The standard practice used in our laboratory to
､･ｴ ｲｭｩｾＬ
the egg -hatch is to leave the oviposition
ｭ｡ｾ･ｲｩ｡ｬ
Fig. 16.
Plastic lemon and orang. molds and polyethylene
freezer jars used for the Medfly oviposition.
-76in the cage with th e flies for 24 hours .
The eggs are then
washed out and incubated on moist filter paper in petri
dishes for 48 hours at room temperature (about 25°C) to determine the egg-hatch.
In past experiments, we used lemon
and orange molds for oviposition and the egg-hatch was recorded low and very erratic.
On the other hand, the use of
polyethylene jars always gave high and constant egg-hatch.
It was suspected that low egg-hatch with the use
of lemons and oranges as oviposition medium was due to low
ｾｵｭｩ､ ｴｹ
inside these molds during the oviposition period ,
rather than any toxic effect of the plastic itself on the
eggs.
A series of experiments was conducted to determine
the adverse effect of low humidities on the egg-hatch of the
Medfly.
Tables
The results of these experiments are presented in
25, 26, 27, 28 , 29 and 30.
In the first experiment, two sets of oviposition
devices were tried.
One set consisted of plastic jars, lemons
and oranges r insed with tap water and the
and oranges.
ｾｴｨ･ｲ
of dry lemons
The oviposition was allowed for 24 hours.
The
eggs were then washed out and incubated on moist filter paper
unt il hatched (for 48 hours).
daily for a week.
in Table 25.
The egg collections were made
The results of this experiment are given
The data indicate clearly that moistened or-
anges and lemons gave a higher percent egg-hatch than dry ones.
The rinsed plastic jars gave the best egg-hatch (87 .4 percent) .
-77Table 25
ｅｦｾｴ
of various kinds of oviposition devices
on the egg-hatch of the Medfly
Ovipisition devices
Total N°of
eggs examined
%
hatched a)
Moist plastic jars
Moist plastic oranges
Moist plastic lemons
7941
7282
7706
87.4
45.2
Dry plastic oranges
Dry plastic lemons
6264
5817
17. 0
14.8
a)
31 • 7
Average of four replications .
The water rinsed oranges and lemons did not give as high a
percentage egg-hatch as the water rinsed plastic jars.
This
is probably due to the dry atmosphere inside the oranges and
lemons.
After rinsing , the water did not stay inside the
lemons and oranges, but instead dripped down through the openi n g t hrou g h which th e ru b b er stoppe r s we re plu g ged . as th e
stoppers were not water tight.
In the plastic jars after
rinsing, the water adhering to the inside surface of t h e
jars dripped down and collected in the bottom of the jars
in the bakelite caps.
This water supplied a very high hum-
idity inside the jars throught the oviposition period of
24 hours .
In order to prove that low egg-hatch in 'wa t e r rinsed
lemons and oranges was due to lack of water retention inside
these molds,
the second experiment was conducted in which 3-4 ml
-78of water was placed in small plastic containers glued over the
top of the rubber stoppers.
Oranges and lemon. with such de-
vices were called humid oranges and lemons.
The results of
this experiment are presented in Table 26.
It is evident
from these data that the humid oranges and lemons with water
inside gave high egg-hatch respectively -
78.0 percent and 86.6 percent,
close to the percentage of egg-hatch in moist
plastic jars (91.1 percent), while the egg-hatch in the water
rinsed oranges and lemons was 57 .1 and 70.8 percent , respectively.
Table 26
Effect of humidity inside ovip osition devices
on the egg-hatch of the Medfly
Oviposition devices
Moist plastic jar
Moist plastic orange
Moist plastic lemon
Dry plastic orange
Dry plastic lemon
Humid plastic orange*
Humid plastic lemon*
*
Total N°of
eggs examined
%
hatched
1777
820
1063
91. 1
851
530
32.1
2 7.2
1122
125 7
78. 0
86.6
57 .1
70.8
A small amount (3-4 ml) of water was put in plastic receptacles inside the orange and lemon molds, and glued over
the rubber stoppers.
In order to further prove that the low percent 'egg-hatch
in water rinsed plastic lemons and oranges
ｷ｡ｳｭｾｲ･ｬｹ
due to
low humidity inside them, rather than any possible toxic effect
of the plast ic on the eggs , the third experiment was carried out.
-79.In this experiment, water r i n s e d lemons and o ran ges were
used f or oviposition.
Egg laying wa.s allowed for one hour.
The lemons and oranges were removed at the end of the ovipaot ion, and were stored under two .d i f f e r e n t
cond itions.
One
group was s tored at room humidity (50-60 percent) and the
othe r one at 100 percent humidity ( inside a desiccator containing distilled water) .
From each group, the eggs were
washed out at an interval of every two hours, until 24 hours ,
and p laced on moist filter paper in petri dishes to examine
the egg-hatch .
The results of this experiment are summarized
and presented in Table 27 .
Table 27
Eff ect o f humidity during incubation period
on the egg-hatch of the Medfly
Period
of
incubation
0
2
4
6
8
10
12
14
16
18
20
22
24
*
hr
hrs
hrs
hrs
hrs
hrs
hrs
h rs
hrs
hra
hrs
hr
s
hrs
Average percent of egg-hatch
100% humidity
ａｾｭｯｳｰｨ･ｲｩ｣
humidity*
oranges
lemons
lemons
oranzes
9 4 .7
9 4.3
94.5
9 1. 9
78.4
88.2
54.7
4 0. 1
35.5
7.8
6.3
2. 4
2.0
50-60 percent .
93 . 0
86.1
91.3
90.6
78.9
83.8
81.5
32.6
21.3
3 .2
1. 7
0.5
0.0
87.7
90.4
8 4.7
93.7
94.3
86.6
94 . 3
95 .0
94 . 5
9 1.6
95 .6
96 .7
87 .9
88 .9
91.9
92. 1
96 .0
85 .3
88.3
90 .5
94.5
94 . 7
90 . 5
95.1
88.0
91.8
-80The results clearly indicate that lower egg-hatch
in rinsed lemons and oranges is merely due to low humidity
inside them.
The oranges and lemons stored at 100 percent
humidity gave normal
･ｧ ｾｨ｡ｴ｣ｨ
to incubation of 24 hours.
(84.7-96.7 percent) even up
Those stored at room humidity
however, gave normal egg-hatch up to 10 hours of incubation .
After this period, the percent of egg-hatch was
lowered (54.7-0.0 percent).
｣ｯｾｳｩ､･ｲ｡｢ｬｹ
The results of this experiment
indicate that whenever we are forced to use plastic lemons
or oranges as oviposition medium, due to use of small sized
cages, we must wash out the eggs before 10 hours after oviposition.
Experiment 4, as shown in Table 28 , was carried out
to determine the maximum period of egg incubation in our
laboratory (at atmospheric humidity of 50 -60 percent) without lowering the percent egg-hatch.
In this experiment, the
oviposition was allowed for one hour in dry plastic jars.
The eggs were shaken off dry from these jars and incubated
0-24 hours in dry petri dishes.
The eggs were moistened
every two hours for 24 hours and put on damp filter paper
to determine the percentage hatched.
The results in Table 28 indicate that under our
laboraiory conditions of 25°C temperature and 50-60 percent
humidity, eggs can stay normal up to 8 hours without lowering
hatchability .
The results of this and the previous experiment
(Table 27) indicate that under our laboratory conditions, oviposition should not be allowed beyond 8-10 hours in plastic
- 81 lemons and o ranges.
Ovipos i t io n periods longer than 8-10
hours reduced the percent egg-hatch due to desiccation of
t h e eggs i n si d e the ovipos i t ion med ium .
Table 28
Effect o f room humidity dur ing incubation
on the egg-hatch of the Medfly
Incubation
period*
Expt I
Percent of egg-hatch
Expt II
Average
0
2
4
6
8
10
12
14
16
18
20
22
24
hI'
hrs
hra
hrs
hrs
hrs
hI'S
hrs
hrs
hI'S
hI's
*
Eggs were incubated for the desired length of periods at
atmospheric humidity of 50-60 .percent, before putting on
moist ｦ ｩ ｬ ｴ ･ ｾ
paper until hatched.
81. 0
87.3
84.9
90.9
80.1
47.5
5.6
6. 6
0.0
hI'S
hI'S
0.0
91.5
90.8
96.2
94.8
9.4.4
34.9
19.6
8.8
4 .1
3.5
86.3
89 .0
90.6
92.8
87 .2
41.2
12.6
8.8
5.4
3.5
2.8
2 .9
0.7
1. 4
0 .3
1. 4
It has been found that i n an incubation of eggs at
atmospheri c hum idity of 50 -60 percent, normal hatch occurs
only up to 8 hours (Table 28).
In the next experiment, effect
of incubation of eggs for 24 hours at five different high humidities was stud ied on the egg-hatch.
The humidities of 75.5,
85.0. 92 .5, 97,5 and 100 percents were created in desiccators
by saturated salt solutions of sodium chloride. potassium
-82chloride . potassium nitrate . potassium sulfate and distilled
water , respectively .
Eggs laid in d ry plastic jars were put in open dry
petri dishes inside the desiccators.
cubation at the different humidities
After 24 hours of int
ｴｨ･
ﾷ ｾ Ｎ･ｧｳ
were moistened
and transferred to wet filter paper for further incubation
for 48 hours to determine the percent hatched.
ment was repeated five times.
The experi-
The results of these experi'\
me nts a re s ummarized in Table 29.
The results indicate that the normal egg-hatch
( 9 3 . 0 percent) occurred from 100 to 92.5 percent humidity.
At 85 .0 percent humidity, only 1.8 percent eggs -hatched, and
none were recorded at the 75.5 percent h umi di t y le vel.
Tabl e 29
Effect of various humidities during Ln c ub at ion '* on
egg-hatch of the Medfly
Percent
humidities
Expt
I
ｅｾｩｴ
check
100.0
97 . 5
9 2. 5
\8 5 . 0
ＷＵ
Ｌｾ 5
93.3
95.5
87.9
95.2
3. 9
0 .0
85 .6
77 .6
77.6
86 .0
2 .6
0.0
'*
!
Percent of egg-hatch
Expt
Expt
Expt
V
III
IV
For a period of 24 ho u rs . ,
95.3
94.6
93.4
90.2
0.6
0.0
95.1
94.2
9 3 .2
93.9
1 •a
0.0
93.2
96.5
96 . 1
9 4 .9
0.7
0.0
Average
92.5
91. 7
89.6
93 .0
1. 8
0 .0
-83:Th e incubation of eggs for 24 hOUTS at 85 and 75.5
percent
ｨｾｭｩ､ ｴｩ･ｳ
is fatal for the Medfly eggs.
The next
experiment was designed to study the maximum incubation for
Medfly eggs at these humidities without lowering the percent
of egg-hatch .
in Table 30.
The results of this experiment are presented
It is evident from the data that incubation of
eggs at 75.5 and 85 percent humidities has no adverse effect
on its hatch up to 8 and 12 hours, respectively.
Table 3 0
Effect of incubat ion of Medfly eggs in low
humidities for va rious ' l e n g t h s of time on hatchability
Length
of incubation
Percent of egg-hatch
75 percent humidity
85 percent humidity
Expt
Expt
AverExpt
Expt
AverII
I
II
I
age
age
2 hr s
4 hra
6 hra
8 hr s
10 hrs
12 hrs
14 h r s
16 hrs
1 8 hrs
20 hrs
22 hrs
24 hrs
93.8
89.0
89.0
93 .9
84.9
90 . 7
75. 3
750 3
87 .0
80.0
56 .3
59.5
96 . 6
92.2
92. 1
87.4
8 1.8
90 .3
86.3
84 . 3
89.2
75.0
76.6
65 .0
95.2
90.6
90.6
90.6
83.4
90.5
80.8
79 .8
88 .1
77 . 5
66 .4
62.2
92. 9
85.1
85.9
84 . 5
69.3
53. 7
36. 1
23.3
20.2
10 .5
0.8
2 .2
95 .7
90 .4
88.8
88 .3
71.4
63 .3
33.2
26 .7
1 2. 3
1 0 03
4.4
2.6
94.3
87.8
87.4
86.4
70.4
58.5
34 .6
25.0
16 .2
10 .4
206
2 .4
The resul ts of all these experiments (Tables 25 , 26 ,
2 7 , 2 8 , 2 9 an d 30 ) in dic at e th at in Med f l y ex pe ri ment s un d er
our laboratory conditions (25°C and 50-60 percent humidity)
whenever wa ter
｣ｾｮ ｯｴ
be maintained consistently inside the
ov iposition medium, the eggs must be washed out within 8 hours
-84of oviposition.
A period longer than 8 hours will lower
ｆｯｲｴｵｮ｡ｴ･ｬｹｾ
the hatchability due to desiccation of the eggs.
with the use of plast ic freezer . jars as oviposition medium,
the problem of egg desiccation does not arise.
When the jars
are rinsed with tap water, a good amount of it collects down
in the bo ttom of the jars in the bakelite screw caps.
This
water keeps the atmosphere inside the jars saturated with
humidity during the oviposition period .
3.
Evaluation of the Performance of Four Different
Types of Yeasts in the Larval Diet of the Medfly.
The insect control or eradication program by the
sterile male technique needs rearing of the adults in the
laboratory in large quantities for field release.
In our
coope rat ive project with OIRSA on the Medfly problem in Central America, the flies are being reared in the laboratory
in mil lions for ir radiation and later release in , the field.
The larval food is the most expensive item beside the labor
and equipment in Medfly rearing.
The standard formula for
the la rval diet consists of:
Dry c a r r ot p owder
Dry brewer's yeast powde r
Sodium benzoate (to inhibit molds)
Cone. HCI ( to bring pH 4 to 4.5)
Tap wate r
The ma jor cost i n l a r v a l
powder and the yeast.
100 gm
25
1-2
4-6 ml
500-600
food comes from the carrot
Sodium benzoate and hydrochloric acid
const itute o n l y a v e r y small fr a c ti o n of the total food cost .
-85Currently we are u.ing Fleischman 's pure primary-grown dry
yeast type 300-B. obtained from Standard Brands, at a price
of $0 . 6 2 per lb.
In the present experiment , Fleischman 's pure primary-grown dry yeast type 2019, Fleischman's yeast ' extract
type 3 and Lake States dried torula yeast USP XV type CF
(F) ｷ ｾ ｲ
tried in the larval ｾ ｩ ･ ｴ
' t o rear the Medfly.
2
The
objective was to find out some cheap yeast which wili better
or equal the performance of the currently used type 300-B.
Type 2019
ｩｾ
the cheapest yeast ($0 . 4 1 per lb, plus freight)
produced by Standard Brands.
Torula is produced by Lake
States yeast and chemical division of the St. Regis Paper Co .
in Wisconsin.
Its price is $0.21 per lb, plus freight.
Yeast
extract type 3 is also a Standard Brands product and costs
$2.48 per lb, plus freight.
The reason for the inclusion of
yeast extract type 3. although so much more expensive, was
to see if it would give a higher percent pupal yield from the
larval medium as compared to the other types .
Larval diet was prepared according to the formula
given prev iously.
Three thousand eggs were put on about
350 ml of this diet, i.e., at the rate of 9000 eggs per liter
of larval medium.
Each treatment was replicated six times.
The data were taken on average weight per pupa, total number of pupae recovered , percent adult emergence from the
pupae, egg fertility and fecundity of females and the longevity of the adults.
The rearing was carried up to the
-86second generation.
The results of these experiments are
summarized and presented in Tables 31, 32, 33 , 34, 35, 36,
37 and 38.
Average weights per pupa of all the treatments for
the two generations are presented in Table 31.
The data in-
dicate that so far as pupal weight is concerned, there is
no difference up to the second generation in any treatment.
Pupae from all the yeasts weighed on an average , 8 mg per
pupa.
ｔｨ
ｾ
results on the effect of the different types
of yeast used in the larval diet on the total pupal recovery
are presented in Table 32.
The , data indicate that except
for type 3, all yeasts gave more than 50 percent pupal recovery .
Ta b l e 31
Effect of different types of yeasts given in the larval diet for
two successive generations on the weight a) of the Medfly pupae
Types
of
yeast
Torula
Genera tion
Av wt of each pupa b ) in mg .
Rep
Rep
Rep
Rep
Rep
Rep
I
II
III
IV
V
Average
VI
8.43
7. 9 1
8 .33
8 .22
7.0 4
8 .00
8.27
II
7. 9 3
7.85
8.7 1
8.18
8 .30
8 .02
8.20
I
II
7 .72
8 .09
8.63
8 .08
8.08
8.26
8.00
8.73
7 . 70
8.09
7. 98
7.90
8.04
8.17
20 19
I
II
7 . 22
8.08
7.38
7.85
7. 6 8
7.82
7.58
7 . 82
7.69
8.77
7.88
8.67
7.57
8.17
Type 3
I
II
7.98
8.11
8 .17
8.26
8 .02
7.97
7. 91
8.01
8.39
8.10
8 .19
8.07
8 .04
300 -B
a)
b)
I
7. 5 9
Based on pupal age of 48 hours.
Based on average weights of 100 pupae
-87Table 32
Effect of different yeasts given in the larval diet for two
successive generations on the pupal recovery of the Medfly
Types
of
yeast
N° of pupae recovered from each
Generatian
Rep
I
Torula
I
II
tray of larval medium a)
Rep
Rep
Rep
Rep
V
Rep
I
II
VI
I
II
IV
1322
2276
1453
2553
1747
2159
1806
2394
1 7 25
1378
1600
1512
1609
2029
1819
64
70
2159
12 76
1655
933
1688
933
1629
933
1982
806
21 0 0
11 0 6
1869
998
1434
74
34
2 162
1276
1924
1100
1688
1544
1629
1570
2287
1 9 89
1982
176 7
1945
1541
1783
77
53
1100
1512
10 4 1
1394
500
629
806
688
924
283
924
417
882
821
852
Av
Type 3
I
II
Av
a)
%
pupal
recovery
III
Av
2019
of
pupae
II
Av
300-B
Av N°
35
28
Each t ray contained 1/3 liter of larval medium on which
3000 eggs were applied .
The low (34 percent) pupal recovery in the second generation
with type 300-B is due to fungus growth in the larval medium
in its four replicates.
The average pupal yield per liter
of larval medium for the two generations in torula, type 2019,
type 300-B and type 3, is 5457, 5349, 4302 and 2556 pupae,
respectively .
These data indicate
｣ｬ･｡ｾｬｹ
that either torula
or type 2019 can be used effectively in place of the currently
used type 300=B for Medfly r e a ri n g , without lowering the
pupal recovery from the larval medium.
-88The adult emergence from the pupae is fairly high
(73-96 percent) in all the treatments (Table
Ｓｾ
Ｎ
No adverse
effect was noticed on adult emergence from any yeast tested
in the experiments.
Table 33
Effect of various yeasts in larval diet on the adult emergence
of the MedflYt tested for two successive generations
Percent adult .erne rgence a)
1st generation
2nd generation
Types of yeast
Torula
91.8
96.0
300-B
91. 7
76.8
20 19
88.8
72. 6
Type 3
94.3
87.8
a)
Based on six replicates .
100 pupae.
Each replicate consisted of
Table 34
Effect of various yeasts in larval diet on the egg fertility
of adult Medflies tested for two successive generations.
Types of
yeast
1st generation
Total N° of
%
eggs exam- hatched
ined
2nd generation
%
Total N°of
eggs exam- hatched
ined
Torula
13481
9 1.0
13986
92.0
300-B
12 4 14
93 . 0
758 7
92 . 0
2019
13705
94 . 2
10418
83 .6
Type 3
12050
9 1. 1
11722
93.7
-89 S imil arly , th e pe r cen tage of egg -hat c h was v e r y
high (84-94 percent ) in al l
the treatments (Table 34).
Thus
fert ility of the ad ults i s not r e d u c e d by the use of any of
t h e yeasts tested.
Data on the daily adult mortality were recorded
fo r each sex.
The ave rage numbe r of females l iving in a
particular week was calculated from the number of females
a li ve on the first and last day of that week .
Th is average
n umber of females per week was used later to calculate the
average number of eggs produced per female per week.
da ily egg production was recorded volumetrically for
treatment.
The
･｡ｾｨ
The number of eggs was calculated on the basis
of 0.01 ml equal t o 330 eggs .
The egg colle c t i o n wa s s ta rted
when the flies were one week old, and was contin ued for four
weeks.
The average number of eggs produced per female per
week for the different treatments is summarized i n Tab les 35
and 36 for the first and second generations, respectively .
The results shown in Table 35 indicate that in the
firs t
ge ne ra t ion , t or ula a n d t ype 300-B ga ve on a n a v e ra g e
70 0 eggs, while type 2019 and type-3 gave 800 eggs pe r female
dur ing thei r fou r weeks of ovipos i tion.
In the second gener -
a t ion, ex cept for type 300-B, all treatments yie lded 600 eggs
per female d ur ing the fo u r weeks of ov iposition .
egg-y ield (202)
The l ow
i n the case of 300-B was not real, as this i s
the s tandard yeast used in our laboratory for the last five
years fo r the rearing of th e Medfl y .
-90Table 35
Effect of different types of yeast given in the larval diet
on the fecundity of adult Medfly females of the first generation
NG of eggs laid per female*per week during
Treatments
1st
week
Torula
300 -B
'2 0 1 9
Type 3
*
different weeks of oviposition
4th
2nd
3rd
week
week
week
Total
Rep
I
Rep II
Average
196
154
176
185
310
248
129
249
189
88
85
87
700
Rep
I
Rep II
Average
136
194
166
212
255
234
168
188
178
103
130
117
695
Rep
I
Rep II
Average
237
202
220
285
306
296
149
232
191
120
97
109
816
Rep
I
Rep II
Average
126
124
125
3 19
305
312
225
250
238
88
1 74
131
B06
Based on 107-127 females laying eggs in the first week, and
30 -89 females laying eggs in the fourth week of oviposition .
The results of Tables 35 and 36 also indicate that
Medfly females lay the largest number of eggs in the second
week of oviposition.
It can be concluded from these results
that the females from the larvae reared on torula or type
20 19 produce at least an equal number of eggs as produced by
the females from type 300-B, if not more.
Thus, these pro-
ducts could be substituted successfully for the type 300-B
without lowering the egg production capacity of the females.
The adult mortality recorded daily for each sex
is summarized in Tables 37 and 38 for the first and second
generation of fl ies, rrspect ively.
The data indicate no
-91 Table 36
Effect of different types of yeast g iven in the larval diet
on t h e fecundity of the adult Medfly " females of the second generation
Treatments
1st
week
Torula
30 0-B
2 0 19
Type 3
*
eggs laid per female* per week in
different periods of oviposition
2nd
3rd
4th
week
week
week
Total
Rep I
Rep I I
Average
168
128
148
205
215
210
14 9
136
143
148
89
124
Rep
I
Rep I I
Average
65
80
73
82
101
92
21
11
40
o
31
6
202
Rep
I
Rep II
Average
199
129
164
274
190
232
145
148
147
51
82
67
610
Rep
I
Rep II
Average
154
143
250
199
225
135
132
134
70
82
76
584
149
6 25
Based on 45-93 females laying eggs in the first week and
4-19 females laying eggs in the fourth week .
noticeab le adverse effect on the longevity of the adults in
any treatment.
The flies coming from the larvae reared on
tor u la, type 2019 or type 3 live as long as those reared on
type 300=B.
As a general rule, the males die more
than fema les in all the treatments.
ｾ｡ｰｩ､
ｬｹ
In type 2019, in the
f irs t gene ration, the female mortality i s c o n s i d e r a b l y l o we r
than in any other treatment, but this trend is not noticed
in the second generation flies.
From the results of this series of experiments , it
is concluded that either torula or type 20 19 can be used
-92satisfactorily for Medfly rearing .
Use of any of these yeasts
did not affect adversely the weight of the individual pupa,
percent of pupal recovery from the larval medium, adult emergence from the pupae, fertility of the females,
the egg-laying
capacity of the females, and the longevity of the adults.
The type 3 yeast tested in these experiments is unsuitable
for mass rearing of this fly, ·primarily because of its expense
as compared to torula or type 2019.
pupal recovery from the
ｬ｡ｲｶ｡ｬｾ･､ｩｵｭ
Secondly, the percent
is low with this yeast .
Thirdly, larval and pupal period is prolonged by two days at
each stage, when type 3 is used .in the larval food.
At present, type 30Q-B is being used by the OIRSA
laboratory for mass rearing of the Medfly .
The use of torula
yeast ($0.21 per lb) in place of type 300-B ($0 . 6 2 per lb) in
the larval food, will
ｲ･ｳｵｬｾｩｮ
a 66 percent saving in yeast
cost for the Medfly rearing .
Production of one million pupae requires about
$25 of the 300-B yeast type.
yeast is about $9. 00 .
However, the cost of torula
Thus, the use of torula yeast will save
about $16 per million pupal production.
producing about 20 million pupae a month.
At present, OIRSA is
At this rate of
fly production, the use of torula will give a saving of about
$3200 per year.
-93Table 37
Effect of va rious yeasts given in larval d iet on the longevity
of the adult Medfly of the first generation ·
Treatment
Sex
Torula
0--+
Sf
30 0- B
ｾ
2019
!f
•
ｾ
Type 3
t»
f}
*
% accumulated mortality· at successive weeks
2nd
3rd
1st
4th
5th
week
week
week
week
week
14.0
4.6
40.5
9.9
74.9
32.6
51.1
100 . 0
97 . 1
11. 7
3.3
28.9
11. B
78 .7
58.2
95 . 0
64.2
100 . 0
8 3.4
20 . 1
2. 5
58.0
4.6
89.7
17.1
97.3
29.6
1 00 . 0
50 .0
8.9
4.5
29.5
11. 0
74.3
34.6
93.8
56.8
98 .5
66.2
Average of tw o replicates.
12 5.-150 fl ies .
95.5
Each replicate c onsist ed o f
Table 38
Eff e ct of vari ous y e asts given in the larval diet on the longevity of th e adult Medfly of the second generation
Treatment
Torula
300 -B
20 19
Type 3
*
Sex
ｾ
ｾ
ｾ
ｾ
0-7
ｾ
9ｾ
% accumulated mortality· at , successive weeks
3rd
1st
2nd
4th
5th
week
week
week
week
week
11.5
7.7
60 . 5
15.2
88.8
45 . 5
99 . 5
72 .2
99 .5
84.8
12.7
6.8
44.8
16.6
83.3
57.8
96.5
83.9
99. 4
93.4
20. 1
10.8
46.9
24. 0
85.2
62.3
99.3
85. 8
100 . 0
94 . 8
5 .3
4.6
35.6
14.6
84.9
42.4
96.9
72.1 '.
Based on two replications.
100 flies
99. 5
88 .3
Each replicate consisted of
-944.
A Note on the Progress of the Cooperative Project
with OIRSA .on the Medfly.
According to our agreement with OIRSA in the Medf l y project. we have furnished all the basic information
needed for the field releases (e.g., sterilization dose ,
overflooding ratio, etc.).
OIRSA has been carrying out
large scale field tests since 1963.
In th e P un t a re n a s t e s t,
the initial fruit infestation was 85 percent in September
1963.
In September 1964, a year after the sterile male re-
leases, the infestation in the same area had dropped to
three percent (as reported by OIRSA)
OIRSA previously had a grant from AID for the initiation of the Medfly project.
Recently . they have received
a new grant from the International Atomic Energy AGency to
continue this program in Central America.
The release of
sterile flies will now be extended to Nicaragua and Panama .
As we have fulfilled our agreement with OIRSA, the
laboratory wo rk on the Medfly will be gradually phased out
unless other basic information will be required by OIRSA.
The cobalt-60 source in o ur laboratory is being used by the
OIRSA l a b o r at o r y rather extens ively, and they will keep on
using th is fac ility.
It is est imated that about 4 million
pupae are irradiated weekly .