Studies on the Effect of Three Species of Heliotropium on the Life

Studies on the Effect of Three Species of Heliotropium on the Life
System of Solitary Desert Locust Schistocerca gregaria (Forskål)
(Orthoptera: Acrididae)
By
Atiyat Abdalla Fadoul Nori
B.Sc. (Honour) Agricultural Studies, University Of Sudan Of Science
And Technology (١٩٩٦)
A thesis submitted in partial fulfillment of the requirements for the
master degree of science in Agricultural
Faculty Of Agriculture
University Of Khartoum
٢٠٠٣
DEDICATION
I would like to dedicate this thesis to
My lovely family with my sincere
appreciation
and love.
AKNOWLEDGEMENTS
I would like to express my sincere appreciation and thanks to my
supervisor, Professor Magzoub Omer Bashir for his supervision, guidance,
encouragement and for providing many facilities.
My deep thanks are due to the Red Sea University management for
offering me the scholarship and financial needs to conduct this study.
My deep thanks are also due to the staff members of Applied
Science Faculty, especially Dr. Salah Mergany the Dean of the faculty, the
Computer department and the Biology department for their patience,
understanding, helping and enthusiasm.
I am greatly indebted to Dr. Ahmed Abdelaziz for helping me to have this
chance while he was the Dean of Applied Science Faculty.
Thanks are also due to the staff members of ICIPE field station, Locust
Research Program, Port Sudan, for helping and providing facilities.
Thanks are extended to Mr. Sidi wad Ali Ph.D student and Mr.
Adnan Khan M.Sc student University of Khartoum, ICIPE field Station for
their helping hints.
I am greatly indebted to Ustaz Nahid Abdalrahim, Faculty of
Marine Science, Red Sea University and Ibrahim Tahir M.Sc Student
Faculty Statistics of Gaezira University for helping me to understand SPSS
analysis program.
Special thanks are due to the staff member’s of the computer lab of
the Red Sea University for providing many facilities.
My sincere thanks are due to my friends and colleagues for their
help, encouragement and cooperation.
Also my sincere thanks are due to my family for their patience and
support.
Finally I render my all thanks to almighty “Alla”
LIST OF CONTENT
Page
Dedication……………………………………………………….
i
Acknowledgments………………………………………………
ii
List of contents………………………………………………….
iv
List of tables……………………………………………………..
vii
List of figures……………………………………………………
xi
List of plates……………………………………………………..
xvi
Abstract………………………………………………………….
xvii
Arabic abstract………………………………………………….
xx
Introduction……………………………………………………..
١
Literature Review……………………………………………….
٥
١ Host plant……………………………………………………..
٥
٢ The locust……………………………………………………..
٦
٢٫١ Identification…………………………………………………
٦
٢٫٢ Desert locust
٦
classification…………………………………...
٧
٢٫٣ Distribution…………………………………………………..
٨
٢٫٤ Locust habitats……………………………………………….
٩
٢٫٤٫١ Habitats of Solitarious Desert Locust……………………..
١٠
٢٫٥ Economic
١١
importance………………………………………...
١٣
٢٫٦ Life
١٤
cycle……………………………………………………..
١٥
٢٫٧ Behaviour…………………………………………………….
١٧
٢٫٨ Host plant…………………………………………………….
١٩
٢٫٨٫١ Host finding………………………………………………
٢٤
٢٫٨٫٢ Factor’s in food selection…………………………………
٢٫٨٫٣ Effect of the food on the biology………………………….
Materials And Methods………………………………………...
٢٤
١ Effect of Heliotropium spp. on the duration period,
٣٠
development period, weight, maturation, longevity,
٣٢
percentage survival and feeding rate………………………….
٣٢
١٫٢
Effect
Of
Heliotropium
spp
on
oviposition…………………..
٣٢
٢ Antifeedant experiments………………………………………
٣٦
٢٫١ Feeding on three species of Heliotropium………………......
٣٧
٢٫٢ Feeding on filter paper impregnated with juices of
٤٠
Heliotropium.
……………………………………………………
٤٠
٣ Repellence experiment……………………………………….
٤٠
٤ Data analysis………………………………………………….
٤٠
Results…………………………………………………………...
٤١
١ Effect of Heliotropium spp on the development of Solitary
٤٦
DL nymphs…………………………………………………..
٤٦
١٫١ Duration period ……………………………………………...
٥٢
١٫١٫١ Season ١٩٩٩-
٥٢
٢٠٠٠………………………………………….
٥٢
١٫١٫٢ Season ٢٠٠٠-
٥٩
٢٠٠١………………………………………….
٦٨
١٫٢ Developmental period………………………………………..
٦٨
١٫٢٫١ Season ١٩٩٩-
٦٨
٢٠٠٠………………………………………….
٦٨
١٫٢٫٢ Season ٢٠٠٠-
٧٣
٢٠٠١………………………………………….
٧٣
١٫٣ Weight of nymphs and fledglings……………………………
٧٤
١٫٣٫١ Season ١٩٩٩-
٧٤
٢٠٠٠………………………………………….
٨١
١٫٣٫٢ Season ٢٠٠٠-
٨١
٢٠٠١………………………………………….
٨١
١٫٤ Maturation ……………………..……………………………
٨٦
١٫٤٫١ Season ١٩٩٩-
٨٦
٢٠٠٠………………………………………….
٨٦
١٫٤٫٢ Season ٢٠٠٠-
٩٥
٢٠٠١………………………………………….
١٠١
١٫٥ Fecundity and
١٠١
fertility………………………………………..
١٠٦
١٫٥٫١ Season ١٩٩٩-
١١٧
٢٠٠٠………………………………………….
١٢٨
١٫٥٫٢ Season ٢٠٠٠-
١٣٧
٢٠٠١………………………………………….
١٤٠
١٫٦ Longevity…………………………………………………….
١٥٢
٦٫١ Season ١٩٩٩-
٢١٧
٢٠٠٠……………………………………………
١٫٦٫٢ Season ٢٠٠٠٢٠٠١………………………………………….
١٫٧ Percentage survival…………………………………………..
١٫٧٫١ Season ١٩٩٩٢٠٠٠………………………………………….
١٫٧٫٢ Season ٢٠٠٠٢٠٠١………………………………………….
١٫٨ Feeding rate………………………………………………….
١٫٨٫١ Season ١٩٩٩٢٠٠٠………………………………………….
١٫٨٫٢ Season ٢٠٠٠٢٠٠١………………………………………….
٢ Antifeedant behaviour………………………………………….
٤٫١
Consumption weight
food…………………………………….
٤٫٢
Area consumed from impregnated filter
paper……………….
٣ Repellency effect……………………………………………….
Discussion………………………………………………………..
Conclusion……………………………………………………….
References……………………………………………………….
Raw data appendix……………………………………………...
Analysis appendix……………………………………………….
LIST OF TABLE
Table
page
١. Mean duration period in solitary DL nymphs reared on three
species of Heliotropium (Season ١٩٩٩-٢٠٠٠)……………………..…٤٢
٢.
Mean duration period in solitary DL male nymphs reared on
tow species of Heliotropium (Season ١٩٩٩-٢٠٠٠)………….. ………٤٤
٣. Mean duration period in solitary DL female nymphs reared
on tow species of Heliotropium (Season ١٩٩٩-٢٠٠٠)………………..٤٤
٤. Mean Duration period of solitary nymphs of the DL
reared on three species of Heliotropium (Season ٢٠٠٠-٢٠٠١)……….٤٧
٥. Mean duration period of solitary nymphs male of the DL
reared on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)…….…٤٨
٦. Mean duration period of solitary nymphs female of the DL
reared on three species of Heliotropium (Season ٢٠٠٠-٢٠٠١)………٥٠
٧. Mean developmental period (from ١st instar to fledgling) of
solitary of the Desert Locust males and females reared on
tow species of Heliotropium (Season ١٩٩٩-٢٠٠٠)…………………٥٣
٨. Mean developmental period (from ١st instar to fledgling) of
solitary DL males and females reared on three species of
Heliotropium (Season ٢٠٠٠-٢٠٠١)…………………………………..٥٥
٩. Mean weight of solitary DL nymphs and fledgling reared on
three species of Heliotropium (Season ١٩٩٩٢٠٠٠)………………….٥٧
١٠. Mean weight of solitary DL male nymphs and fledgling
reared on three species of Heliotropium (Season ١٩٩٩-٢٠٠٠)………٦٠
١١. Mean weight of solitary DL female nymphs and fledgling
reared on three species of Heliotropium (Season ١٩٩٩٢٠٠٠)……….٦٠
١٢. Mean weight of solitary DL nymphs and fledgling reared
on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)………………٦٢
١٣. Mean weight of solitary DL male nymphs and fledgling
reared on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)………..٦٥
١٤. Mean weight of solitary DL female nymphs and fledgling
reared on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)…..……٦٦
١٥. Onset of maturation solitary DL males and females reared
on tow species of Heliotropium (Season ١٩٩٩٢٠٠٠)………………...٦٩
١٦. Onset of maturation solitary DL males and females reared
on tow species of Heliotropium (Season ٢٠٠٠٢٠٠١)………………...٧١
١٧. Fecundity and fertility of solitary DL female reared on tow
species of Heliotropium (Season ١٩٩٩٢٠٠٠)………………………..٧٥
١٨. Fecundity, fertility and egg development of solitary DL female
reared on tow species of Heliotropium (Season ١٩٩٩٢٠٠٠)…………٧٦
١٩. Fecundity and fertility of solitary DL female reared on tow
species of Heliotropium (Season ٢٠٠٠٢٠٠١)………………………...٧٨
٢٠. Fecundity, fertility and egg development of solitary DL female
reared on tow species of Heliotropium (Season ٢٠٠٠٢٠٠١)…………٧٩
٢١. Mean longevity of solitary DL male and female reared on
three species of Heliotropium (Season ١٩٩٩٢٠٠٠)…………………..٨٢
٢٢. Mean longevity of solitary DL male and female reared on
three species of Heliotropium (Season ٢٠٠٠٢٠٠١)…………………..٨٤
٢٣. Percentage survival of solitary nymphs and fledgling DL
reared on three species of Heliotropium (Season ١٩٩٩٢٠٠٠)……….٨٧
٢٤. Percentage survival of solitary nymphs and fledgling DL
reared on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)……….٨٧
٢٥. Mean weight dry food (gm) consumed by solitary
nymphs and fledgling reared on three species of Heliotropium
(Season ١٩٩٩٢٠٠٠)………………………………………………….٩٠
٢٦. Mean weight wet food (gm) consumed by solitary nymphs
and fledgling reared on three species of Heliotropium
(Season ١٩٩٩-٢٠٠٠)………………………………………………….٩١
٢٧. Mean weight dry food (gm) assimilated by solitary
nymphs and fledgling reared on three species of
Heliotropium (Season ١٩٩٩-٢٠٠٠)………………………………….٩٣
٢٨. Mean weight dry food (gm) consumed by solitary nymphs
and fledgling reared on three species of Heliotropium
(Season ٢٠٠٠-٢٠٠١)…………………………………………………٩٦
٢٩. Mean weight wet food (gm) consumed by solitary nymphs
and fledgling reared on three species of Heliotropium
(Season ٢٠٠٠-٢٠٠١)………………………………………………….٩٧
٣٠. Mean weight dry food (gm) assimilated by solitary nymphs
and fledgling reared on three species of Heliotropium
(Season ٢٠٠٠-٢٠٠١)…………………………………………………٩٩
٣١. Mean weight wet food (gm) consumed by solitary nymphs
and fledgling kept on three species of Heliotropium provided
together in Banks each consisting of ١٠ cells
(٦٠x٢٤x٣٠ cm) during ٢
days………………………………………١٠٢
٣٢. Mean weight wet food (gm) consumed by solitary nymphs
and fledgling kept on three species of Heliotropium provided
together in Banks each consisting of ١٠ cells
(٦٠x٢٤x٣٠ cm) during ٦
days……………………………………….١٠٤
٣٣. Mean weight wet food (gm) consumed by solitary nymphs
and fledgling kept on three species of Heliotropium provided
together in small cages during ٢
days……………………………….١٠٧
٣٤. Mean area of filter paper (cm٢) impregnated with juice of
three species of Heliotropium eaten by solitary ٥th instar
nymphs in ٢٤ hour in large cage (١٠٠ cm diameter),
(Group and paired plant test.)……………………………………….١١٠
٣٥. Mean area of filter paper (cm٢) impregnated with juice of
three species of Heliotropium eaten by solitary ٥th instar
nymphs in ٢٤ hour in small cages (٢٠ cm diameter),
(group and paired plant test.)………………………………………..١١١
٣٦. Mean area of filter paper (cm²) impregnated with the juice
of three species of Heliotropium eaten by solitary male
٥th instar nymphs in ٢٤ hour in small cages (٢٠cm diameter),
(group and paired plant tested)……………………………………..١١٤
٣٧. Mean area of filter paper (cm٢) impregnated with juice
of three species of Heliotropium eaten by solitary ٥th instar
female nymphs in ٢٤ hour in small cages (٢٠ cm diameter),
(group and paired plant test.)………………………………….……١١٥
٣٨. Mean walking, resting and total time and distance traversed
to reach food in wind tunnel by solitary DL male and female
٥th instar
nymphs……………………………………………………١١٨
٣٩. Behavior analysis of solitary DL ٥th instar nymphs in wind
tunnel until food is reached…………………………………………١١٩
٤٠. Mean walking, resting and total time and distance traversed
to reach food in wind tunnel by solitary DL male ٥th instar
nymphs………………………………………………………………١٢
٢
٤١. Behavior analysis of solitary DL ٥th instar nymphs in wind
tunnel until food is
reached………………………………………….١٢٣
٤٢. Mean walking, resting and total time and distance traversed
to reach food in wind tunnel by solitary DL female ٥th instar
nymphs………………………………………………………………١٢
٥
٤٣. Behavior analysis of solitary DL ٥th instar nymphs in wind
tunnel until food is
reached………………………………………….١٢٦
LIST OF FIGURES
Figure
Page
١
Diagram of the flat-bed wind tunnel made of transparent glass;
١.Exhaust fan; ٢. Heliotropium species; ٣. Doors for
introduction and collection of insects; ٤. Ruler ١٤٠ cm long;
٥. Sliding glass door to release the test insect; ٦. Wire mesh box;
٧. Wind tunnel chamber; ٨. Insect test pre-release
compartment…………………………………………………………٣٩
٢
Mean duration period in solitary DL nymphs reared on
three species of Heliotropium (Season ١٩٩٩٢٠٠٠)………………….٤٣
٣
Mean duration period in solitary DL male nymphs reared on
tow species of Heliotropium (Season ١٩٩٩-٢٠٠٠)………...
………...٤٥
٤
Mean duration period in solitary DL female nymphs reared
on tow species of Heliotropium (Season ١٩٩٩-٢٠٠٠)…………
…….٤٥
٥
Mean duration period in solitary DL nymphs reared on three
species of Heliotropium (Season ٢٠٠٠٢٠٠١)………………………..٤٩
٦
Mean duration period in solitary DL male nymphs reared
on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)………..٤٩
٧
Mean duration period in solitary DL female nymphs reared
on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)………..٥١
٨
Mean developmental period of solitary nymphs reared
on tow species of Heliotropium (Season ١٩٩٩٢٠٠٠)…………٥٤
٩
Mean developmental period of solitary nymphs reared on
tow species of Heliotropium (Season ٢٠٠٠-٢٠٠١)……………٥٤
١٠ Mean developmental period of solitary males and females
nymphs reared on three species of Heliotrpium
(Season ١٩٩٩٢٠٠٠)…………………………………………………..٥٦
١١ Mean developmental period of solitary males and females
nymphs reared on three species of Heliotropium
(Season ٢٠٠٠-٢٠٠١)…………………………………………………٥٦
١٢ Mean weight of solitary DL nymphs and fledgling reared
on three species of Heliotropium (Season ١٩٩٩٢٠٠٠)……..…٥٨
١٣ Mean weight of solitary DL male nymphs and fledgling reared
on two species of Heliotropium (Season ١٩٩٩٢٠٠٠)…………٦١
١٤ Mean weight of solitary DL female nymphs and fledgling reared
on two species of Heliotropium (Season ١٩٩٩٢٠٠٠)…………..……٦١
١٥ Mean weight of solitary DL nymphs and fledgling reared
on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)………..٦٣
١٦ Mean weight of solitary DL male nymphs and fledgling reared
on three species of Heliotropium (Season ٢٠٠٠٢٠٠١)………..٦٧
١٧ Mean weight of solitary DL female nymphs and fledgling reared
on three species of Heliotropium (Season ٢٠٠٠-٢٠٠١)… ……٦٧
١٨ Onset of maturation of solitary DL fledgling stage reared
on tow species of Heliotropium (Season ١٩٩٩٢٠٠٠)…………٧٠
١٩ Onset of maturation of solitary DL male and female
fledgling stage reared on tow species of Heliotropium
(Season ١٩٩٩-٢٠٠٠)…………………………………………...٧٠
٢٠ Onset of maturation of solitary DL fledgling stage reared
on tow species of Heliotropium (Season ٢٠٠٠٢٠٠١)…………٧٢
٢١ Onset of maturation of solitary DL male and female
fledgling stage reared on tow species of Heliotropium
(Season ٢٠٠٠٢٠٠١)……………………………………………٧٢
٢٢ Fecundity of solitary female reared on tow species of
Heliotropium (Season ١٩٩٩٢٠٠٠)…………………………….٧٧
٢٣ Fecundity fertility and egg development in egg pods laid
by solitary female reared on tow species of
Heliotropium (Season ١٩٩٩٢٠٠٠)…………………………….٧٧
٢٤ Fecundity of solitary female reared on tow species of
Heliotropium (Season ٢٠٠٠٢٠٠١)…………………………….٨٠
٢٥ Fecundity fertility and egg development in egg pods laid by
solitary female reared on tow species of
Heliotropium (Season ٢٠٠٠-٢٠٠١)……………………………
٨٠
٢٦ Mean longevity of solitary nymphs, fledgling and adult reared
on three species of Heliotropium (Season ١٩٩٩-٢٠٠٠)……….٨٣
٢٧ Mean longevity of solitary males and females nymphs,
fledgling and adult reared on three species of
Heliotropium (Season ١٩٩٩٢٠٠٠)…………………………….٨٣
٢٨ Mean longevity of solitary nymphs, fledgling and adult
reared on three species of Heliotropium
(Season ٢٠٠٠-٢٠٠١)…………………………………………...٨٥
٢٩ Mean longevity of solitary males and females nymphs,
fledgling and adult reared on three species of
Heliotropium (Season ٢٠٠٠٢٠٠١)…………………………….٨٥
٣٠ Survival of solitary DL nymphs and adults reared on three
species of Heliotropium from ٢nd instar to adult
mortality (Season ١٩٩٩-٢٠٠٠)………………………………...٨٨
٣١ Survival of solitary DL nymphs and adults reared on three
species of Heliotropium from ٢nd instar to adult
mortality (Season ٢٠٠٠٢٠٠١)…………………………………٩٢
٣٢ Mean weight dry food consumed by solitary DL nymphs
and fledgling male and female (Season ١٩٩٩٢٠٠٠)…………..٩٢
٣٣ Mean weight wet food consumed by solitary DL nymphs
and fledgling male and female (Season ١٩٩٩٢٠٠٠)…………..٩٤
٣٤ Mean weight dry food assimilated by solitary DL nymphs
and fledgling male and female (Season ١٩٩٩٢٠٠٠)…………..٩٨
٣٥ Mean weight dry food consumed by solitary DL nymphs
and fledgling male and female (Season ٢٠٠٠٢٠٠١)………......٩٨
٣٦ Mean weight wet food consumed by solitary DL nymphs
and fledgling male and female (Season ٢٠٠٠٢٠٠١)…………١٠٠
٣٧ Mean weight dry food assimilated by solitary DL nymphs
and fledgling male and female (Season ٢٠٠٠٢٠٠١)…………١٠٣
٣٨ Mean weight wet food consumed by solitary ٥th instar
nymphs kept on three species of Heliotropium
during ٢ days…………………………………………………١٠٣
٣٩ Mean weight wet food consumed by solitary ٥th instar
male and female nymphs kept on three species of
Heliotropium during ٢
days…………………………………..١٠٥
٤٠ Mean weight wet food consumed by solitary ٥th instar nymphs
kept on three species of Heliotropium during ٦
days………...١٠٥
٤١ Mean weight wet food consumed by solitary ٥th instar male
and female nymphs kept on three species of Heliotropium
during ٦ days…………………………………………...…….١٠٨
٤٢ Mean weight wet food consumed by solitary ٥th instar nymphs
kept on three species of Heliotropium in small cages
during ٢ days……………………………………………..…١١٢
٤٣ Mean eight wet food consumed by solitary ٥th instar male
and female nymphs kept on three species of
Heliotropium in small cages during ٢ days………………….١١٢
٤٤ Mean area of impregnated filter paper eaten in ٢٤hour
by solitary ٥th instar nymphs’ in-group and paired
plant test in large cage (١٠٠ cm diameter)…………………..١١٦
٤٥ Mean area of impregnated filter paper eaten in ٢٤ hour by
solitary ٥th instar nymphs’ in-group and paired plant test in small
cages ( ٢٠ cm diameter).
٤٦ Mean area of impregnated filter paper eaten in ٢٤ hour by solitary ٥th
instar male nymphs’ in-group and paired plant test in small cages (٢٠
cm diameter).
٤٧ Mean area of impregnated filter paper eaten in ٢٤ hour by solitary ٥th
instar female nymphs’ in-group and paired plant test in small cages (٢٠
cm diameter).
٤٨ Mean walking, resting and total time spend by solitary DL nymphs
until food was reached.
٤٩ Behavior analyses of solitary DL ٥th instar nymphs in wind tunnel until
food was reached.
٥٠ Mean walking, resting and total time spend by solitary DL male
nymphs until food was reached.
٥١ Behavior analyses of solitary DL ٥th instar male nymphs in wind tunnel
until food was reached.
٥٢ Mean walking, resting and total time spend by solitary DL female
nymphs until food was reached.
٥٣ Behavior analyses of solitary DL ٥th instar female nymphs in wind
tunnel until food was reached.
LIST OF PLATES
Plate
page
١. a. Heliotropium ovalifolium old plant………………………………..٢٥
b. Heliotropium ovalifolium young plant ……………………………….٢٥
٢. a Heliotropium arabianense old plant ………………………………٢٦
b. Heliotropium arabianense young plant……………………………… ٢٦
٣. Heliotropium lignosum……………………………………………………..٢٧
٤. a Solitary rearing cage in (Season ١٩٩٩-٢٠٠٠)……………………....٢٩
٥. a Solitary rearing cup in (Season ٢٠٠٠-٢٠٠١)………………………..٢٩
٦. a,b Paired cages………………………………………………………٣١
٧. a,b Small cages used for Antifeedant experiments on plants in
feeding………………………………………………………………..٣٣
٨. a,b large cages used for Antifeedant experiment on impregnated
filter paper……………………………………………………………٣٤
٩. Small cage used for Antifeedant experiment on impregnated filter
paper………………………………………………………………….٣٥
١٠. Impregnated filter paper with the juice of A= Heliotropium
ovalifolium, B=Heliotropium arabianense, C=Heliotropium
lignosum……………………………………………………………...٣٨
١١. Impregnated filters paper eaten by solitary ٥th instar nymphs in ٢٤
hour…………………………………………………………………..١٠٩
ABSTRACT
In this study the effect of three species of Heliotropium on the life
system of solitary desert locust was investigated. This genus is the most
important one among all desert plants in the Red Sea zone and forms the
key species in desert locust distribution. There are six species in the area.
Of these, three were used in this study; H. ovalifolium, H. arabianense
and H. lignosum.
All experiments were carried out at the International Centre of
Insect Physiology and Ecology ICIPE, locust program –Port Sudan field
station, during the period ١٩٩٩/٢٠٠٠-٢٠٠٠/٢٠٠١. The plants were collected
from Sallom area ٣٠ Km south west of Port Sudan. The locusts used were
offsprings of the solitary stock bred at ICIPE station.
The effect of the three species on the life system of the DL was
investigated using the parameters of development, weight, survival rate,
feeding rate, maturation and longevity. Also the effect on the female
fertility and fecundity and egg development was studied. The effect of
antifeedant of the three species was carried out in two ways. First by
keeping the locust on the three species in cells and small cages to know
their preference to each species. Secondly by using juice extract from the
plants impregnating on filter papers, and provided to the nymphs in
multiple choice tests. The attraction of the solitary ٥th instar nymphs by
the smell of food plants was carried out in a wind tunnel cage.
The results indicated that the solitary locust nymphs develop well
on H. ovalifolium and H. arabianense while they did not finish their
development on H. lignosum, they died in the fledgling stage or after
fledgling in a maximum of ٢ days. There is no clear effect on the nymphs
weight gain between the three species. Solitary nymphs fed well on H.
ovalifolium and H. arabianenes, while they fed little on H. lignosum. The
fledglings on the first two species matured after a long period. The male
matured before the female. The effect of these two species on the fertility
and fecundity and egg development was in the same manner. Mating take
place after a long period and also the egg laying rate was low compared
to the solitary normal behavior.
From antifeedant experiments it was clear that solitary nymphs fed
on and preferred H. arabianense and H. ovalifolium and didn’t prefer H.
lignosum. While large area was fed from the filter paper impregnated
with H. lignosum juice compared to little areas of H. ovalifolium and H.
arabianense. This indicates that some volatile phagostimulating material
or materials were lost in the process of extracting the juice of H.
arabianense and H. ovalifolium. On the other hand, some volatile
antifeedant material or materials were lost in the process of extracting the
juice of H. lignosum.
This substance or substances need to be investigated and can be used as
antifeedant substances in locust control.
Attractiveness of H. lignosum to the DL was very slow. The tested
individuals rested most of the time, then turned back or changed their
direction in spite of that few numbers walked on for ١٤٠ cm but they
didn’t clime the food or bit it. While the attraction to the other two
species was clear. There is no significant difference regarding behavior
(moving antenna, climbing and walking in many direction) between the
three species.
From this study it is clear that H. ovalifolium and H. arabianense
are important species and can be used as an index in the locust survey.
This makes the survey more limited, save a lot of time and effort. The
wide spread of these species can be indicaters in the study of
gregaraistion and swarming processes.
This would help in obtaining early warning system for proper
management and control strategies. Also the attractiveness of the two
species can be used in the control strategies by incorporating poison in
food traps. The third species volatiles can be extracted and used to repel
locusts from crop plants.
‫ﺍﻟﺨـــــــــﻼﺼﺔ‬
‫ﺘﻡ ﺨﻼل ﻫﺫﻩ ﺍﻟﺩﺭﺍﺴﺔ ﺍﻟﺒﺤﺙ ﻋﻥ ﺘﺄﺜﻴﺭ ﺜﻼﺜﺔ ﺃﻨﻭﺍﻉ ﻤـﻥ ﺠـﻨﺱ ‪Heliotropium‬‬
‫ﻋﻠﻰ ﻨﻅﺎﻡ ﺤﻴﺎﺓ ﺍﻟﺠﺭﺍﺩ ﺍﻟﺼﺤﺭﺍﻭﻱ ﺍﻻﻨﻔﺭﺍﺩﻱ‪ .‬ﻭﻴﻌﺘﺒﺭ ﻫﺫﺍ ﺍﻟﺠﻨﺱ ﻤﻥ ﺃﻫﻡ ﺃﺠﻨـﺎﺱ‬
‫ﺃﻟﻨﺒﺎﺘﺎﺕ ﻓﻲ ﻤﻨﻁﻘﺔ ﺍﻟﺒﺤﺭ ﺃﻷﺤﻤﺭ‪ .‬ﻭﻴﻌﺘﺒﺭ ﺍﻟﺒﻌﺽ ﻤﻔﺘﺎﺡ ﻟﺘﻭﺍﺠﺩ ﺃﻟﺠﺭﺍﺩ ﺒﺎﻟﻤﻨﻁﻘـﺔ‪.‬‬
‫ﺘﻭﺠﺩ ﻤﻨﻪ ﺃﻜﺜﺭ ﻤﻥ ﺴﺘﺔ ﺃﻨﻭﺍﻉ ﺍﺴﺘﺨﺩﻤﺕ ﺜﻼﺜﺔ ﻤﻨﻬﺎ ﻓﻲ ﻫﺫﻩ ﺃﻟﺩﺭﺍﺴﺔ ﻭﻫﻲ ﺃﻷﻜﺜﺭ‬
‫ﺘﻭﺍﺠﺩﺍ ﻓﻲ ﻤﻨﺎﻁﻕ ﺍﻟﺘﻭﺍﻟـﺩ ﻭﻫـﻲ ‪H. ovalifolium, H. arabianense, H.‬‬
‫‪. lignosum‬‬
‫ﺃﺠﺭﻴﺕ ﺠﻤﻴﻊ ﺍﻟﺘﺠﺎﺭﺏ ﺒﺎﻟﻤﺭﻜﺯ ﺍﻟﺩﻭﻟﻲ ﻟﻔـﺴﻴﻭﻟﻭﺠﻴﺎ ﻭﺒﻴﺌـﺔ ﺍﻟﺤـﺸﺭﺍﺕ ‪ICIPE‬‬
‫ﺒﺭﻨﺎﻤﺞ ﺍﻟﺠﺭﺍﺩ ﺍﻟﺼﺤﺭﺍﻭﻱ‪ ،‬ﻤﺤﻁﺔ ﺒﻭﺭ ﺘﺴﻭﺩﺍﻥ‪ .‬ﻓﻲ ﺍﻟﻔﺘﺭﺓ ﻤـﺎﺒﻴﻥ ‪٢٠٠٠/١٩٩٩‬‬
‫– ‪ .٢٠٠١/٢٠٠٠‬ﺠﻤﻌﺕ ﺍﻟﻨﺒﺎﺘﺎﺕ ﺍﻟﻤﺴﺘﺨﺩﻤﺔ ﻓﻲ ﺍﻟﺘﺠﺭﺒﺔ ﻤﻥ ﻤﻨﻁﻘﺔ ﺴـﻠﻭﻡ ‪٣٠ ،‬‬
‫ﻜﻴﻠﻭ ﻤﺘﺭ ﺠﻨﻭﺏ ﻏﺭﺏ ﺒﻭﺭ ﺘﺴﻭﺩﺍﻥ ﻭﺍﺴﺘﺨﺩﻡ ﺍﻟﺠﺭﺍﺩ ﺍﻻﻨﻔﺭﺍﺩﻱ ﻤﻥ ﻤﺯﺍﺭﻉ ﺍﻟﺘﺭﺒﻴﺔ‬
‫ﺍﻟﺨﺎﺼﺔ ﺒﺎﻟﻤﺭﻜﺯ‪ .‬ﺩﺭﺱ ﺘﺄﺜﻴﺭ ﺍﻟﺜﻼﺜﺔ ﺃﻨﻭﺍﻉ ﻋﻠﻰ ﻨﻅﻡ ﺤﻴﺎﺓ ﺍﻟﺠـﺭﺍﺩ ﻤـﻊ ﻤﺘﺎﺒﻌـﺔ‬
‫ﺍﻟﺘﻁﻭﺭ ‪ ،‬ﺍﻟﻭﺯﻥ‪ ،‬ﻨﺴﺒﺔ ﺍﻟﺘﻐﺫﻴﺔ‪ ،‬ﺍﻟﻨﻀﺞ ﺍﻟﺠﻨﺴﻲ ﻭﺍﻟﻘﺩﺭﺓ ﻋﻠﻰ ﺍﻟﺒﻘﺎﺀ‪ .‬ﻜﺫﻟﻙ ﺩﺭﺍﺴـﺔ‬
‫ﺃﺜﺭﻫﺎ ﻋﻠﻲ ﻗﺩﺭﺓ ﺍﻹﻨﺎﺙ ﻋﻠﻰ ﻭﻀﻊ ﺍﻟﺒﻴﺽ ﻭﻤﺩﻯ ﺘﻁﻭﺭ ﺍﻟﺒﻴﺽ ﺍﻟﻨﺎﺘﺞ ﻋﻨﻬﺎ‪ .‬ﻜﻤـﺎ‬
‫ﺘﻤﺕ ﺩﺭﺍﺴﺔ ﻤﻀﺎﺩﺍﺕ ﺍﻟﺘﻐﺫﻴﺔ ﻟﻸﻨﻭﺍﻉ ﺍﻟﺜﻼﺜﺔ ﺒﻁﺭﻴﻘﺘﻴﻥ ‪ ،‬ﺍﻷﻭﻟﻰ ﺒﻭﻀﻊ ﺍﻟﺠﺭﺍﺩ ﻓﻲ‬
‫ﺨﻼﻴﺎ ﺃﻭ ﺃﻗﻔﺎﺹ ﺒﻬﺎ ﺍﻟﺜﻼﺜﺔ ﺃﻨﻭﺍﻉ ﻤﻌﺎ ﻭﻤﻌﺭﻓﺔ ﻤﺩﻯ ﺘﻔﻀﻴﻠﻬﺎ ﻟﻜل ﻨﻭﻉ‪ .‬ﺃﻤﺎ ﺍﻟﺜﺎﻨﻴـﺔ‬
‫ﺒﺎﺴﺘﺨﺩﺍﻡ ﻤﺴﺘﺨﻠﺹ ﻋﺼﻴﺭﻱ ﺜﻡ ﻏﻤﺭ ﺃﻭﺭﺍﻕ ﺍﻟﺘﺭﺸﻴﺢ ﻓﻲ ﺫﻟﻙ ﺍﻟﻤﺴﺘﺨﻠﺹ ﻭﺘﺠﻔﻴﻔﻬﺎ‬
‫ﺜﻡ ﻋﺭﻀﻬﺎ ﻋﻠﻰ ﺍﻟﺤﺸﺭﺍﺕ ﺒﻁﺭﻕ ﻤﺨﺘﻠﻔﺔ‪.‬‬
‫ﻜﻤﺎ ﺘﻤﺕ ﺩﺭﺍﺴﺔ ﻤﺩﻯ ﺍﻨﺠﺫﺍﺏ ﺍﻟﻁﻭﺭ ﺍﻟﺨﺎﻤﺱ ﻟﺭﺍﺌﺤﺔ ﺍﻟﻨﺒﺎﺘﺎﺕ ﺍﻟﻤﺤﻤﻭﻟﺔ ﻤﻊ ﺘﻴـﺎﺭ‬
‫ﺍﻟﻬﻭﺍﺀ ﻓﻲ ﻗﻔﺹ ﺃﻋﺩ ﻟﺫﻟﻙ‪.‬‬
‫ﻤﻥ ﺍﻟﻨﺘﺎﺌﺞ ﺍﻟﻤﺘﺤﺼل ﻋﻠﻴﻬﺎ ﻟﻭﺤﻅ ﺃﻥ ﺃﻁﻭﺍﺭ ﺍﻟﺠﺭﺍﺩ ﺍﻻﻨﻔﺭﺍﺩﻱ ﺘﻜﻤل ﺩﻭﺭﺓ ﺤﻴﺎﺘﻬـﺎ‬
‫ﺒﺼﻭﺭﺓ ﺤﺴﻨﺔ ﻓﻲ ﻨﻭﻋﻴﻥ ﻤﻥ ﺍﻟﻘﺭﻴﺭﺓ ﻫﻤﺎ‪. H. ovalifolium, H. arabianense‬‬
‫ﺒﻴﻨﻤﺎ ﻻ ﺘﺘﻡ ﺩﻭﺭﺓ ﺤﻴﺎﺘﻬﺎ ﻭﺍﻥ ﺃﻜﻤﻠﺕ ﺘﻤﻭﺕ ﺍﻷﻓﺭﺍﺩ ﻓﻲ ﺍﻟﺘﺠﻨﺢ ﺃﻭ ﺒﻌﺩ ﻤﺩﺓ ﺃﻗـﺼﺎﻫﺎ‬
‫ﻴﻭﻤﻴﻥ ﻋﻠﻰ ﺃﻟﻨﻭﻉ‪ . H. lignosum‬ﺃﻭﺯﺍﻥ ﺍﻷﻁﻭﺍﺭ ﻻ ﺘﺘﺄﺜﺭ ﺘﺄﺜﺭﺍ ﻭﺍﻀﺤﺎ ﻤﻥ ﻨﻭﻉ‬
‫ﻵﺨﺭ‪ .‬ﻨﺴﺒﺔ ﺍﻷﻜل ﺍﻟﻤﺴﺘﻬﻠﻙ ﻴﺯﻴﺩ ﻋﻠـﻰ ‪H. ovalifolium, H. arabianense‬‬
‫ﺒﻴﻨﻤﺎ ﻴﻘل ﻋﻠﻲ‪ H. lignosum.‬ﺍﻷﻁﻭﺍﺭ ﺍﻟﻤﺠﻨﺤﺔ ﺘـﺼل ﻟﻠﻁـﻭﺭ ﺍﻟﺒـﺎﻟﻎ ﻋﻠـﻰ‬
‫ﺍﻟﻨﻭﻋﻴﻥ ﺍﻷﻭﻟﻴﻥ ﻭﻟﻜﻥ ﺒﻌﺩ ﻓﺘﺭﺓ ﺯﻤﻨﻴﺔ ﻁﻭﻴﻠﺔ ﻭﺘﺼل ﺍﻟﺫﻜﻭﺭ ﻟﻠﻁﻭﺭ ﺍﻟﺒـﺎﻟﻎ ﻗﺒـل‬
‫ﺍﻹﻨﺎﺙ‪ .‬ﻜﺫﻟﻙ ﺍﻟﻨﻭﻋﻴﻥ ﺍﻟﺴﺎﺒﻘﻴﻥ ﺘﺄﺜﻴﺭﻫﻤﺎ ﻴﻜﻭﻥ ﺒﻨﻔﺱ ﺍﻟﻤـﺴﺘﻭﻯ ﻋﻠـﻰ ﺍﻟﺨـﺼﻭﺒﺔ‬
‫ﻭﺘﻁﻭﺭ ﺍﻟﺒﻴﺽ ﺍﻟﻨﺎﺘﺞ‪ .‬ﻭﻟﻜﻥ ﺒﻌﺩ ﻓﺘﺭﺓ ﻁﻭﻴﻠﺔ ﻤﻥ ﺒﻠﻭﻍ ﺍﻟﻁﻭﺭ ﺍﻟﺴﺎﻭﻱ ﻜﻤﺎ ﺃﻥ ﻨﺴﺒﺔ‬
‫ﻭﻀﻊ ﺍﻟﺒﻴﺽ ﻗﻠﻴﻠﺔ ﻤﻘﺎﺭﻨﺔ ﻤﻊ ﺍﻟﺴﻠﻭﻙ ﺍﻟﻁﺒﻴﻌﻲ ﻟﻠﺠﺭﺍﺩ ﺍﻻﻨﻔﺭﺍﺩﻱ‪.‬‬
‫ﻭﺠﺩ ﺃﻥ ﺃﻟﻌﻤﺭ ﺍﻟﻜﺎﻤل ﻓﻲ ﻫﺫﻴﻥ ﺃﻟﻨﻭﻋﻴﻥ ﻴﻁﻭل ﻭﻴﺼل ﻟﺤﻭﺍﻟﻲ ﺴﺘﺔ ﺍﺸﻬﺭ ﺃﻭ ﺃﻜﺜـﺭ‬
‫ﺒﻴﻨﻤﺎ ﻴﻘﺼﺭ ﺒﺩﺭﺠﺔ ﻭﺍﻀﺤﺔ ﻋﻠﻰ ﺍﻟﻨﻭﻉ ‪H. lignosum‬‬
‫ﻤﻥ ﺘﺠﺎﺭﺏ ﻤﻀﺎﺩﺍﺕ ﺍﻟﺘﻐﺫﻴﺔ ﻴﺘﻀﺢ ﺃﻥ ﺃﻁﻭﺍﺭ ﺍﻟﺠﺭﺍﺩ ﺍﻻﻨﻔﺭﺍﺩﻱ ﺘﺘﻐـﺫﻯ ﻭﺘﻔـﻀل‬
‫ﺍﻟﻨﻭﻋﻴﻥ ‪ H . ovalifolium, H. arabianense‬ﺒﻴﻨﻤﺎ ﺘﺘﻐﺫﻯ ﻋﻠﻰ ﻤﺴﺎﺤﺔ ﻭﺍﺴﻌﺔ‬
‫ﻤﻥ ﺃﻭﺭﺍﻕ ﺍﻟﺘﺭﺸﻴﺢ ﺍﻟﻤﻐﻤﻭﺭﺓ ﻓﻲ ﺍﻟﻤﺴﺘﺨﻠﺹ ﺃﻟﻌـﺼﻴﺭﻱ ﻟﻠﻨـﻭﻉ‪H. lignosum‬‬
‫ﻭﺘﺘﻐﺫﻱ ﻋﻠﻰ ﻤﺴﺎﺤﺎﺕ ﻀﻴﻘﺔ ﺠﺩﺍ ﻤﻥ ﺍﻟﻨﻭﻋﻴﻥ ﺍﻵﺨﺭﻴﻥ‪ .‬ﻤﻥ ﻫﻨﺎ ﻴﺘﻀﺢ ﺃﻥ ﻫـﺫﺍ‬
‫ﺍﻟﻨﻭﻉ ﻴﺤﺘﻭﻱ ﻋﻠﻰ ﻤﻭﺍﺩ ﻁﻴﺎﺭﺓ ﺫﺍﺕ ﺭﺍﺌﺤﺔ ﻤﻤﻴﺯﺓ ﺘﺅﺩﻱ ﺇﻟﻰ ﻨﻔﻭﺭ ﺍﻟﺠـﺭﺍﺩ ﻤﻨـﻪ‬
‫ﻭﻋﻨﺩﻤﺎ ﺘﻔﻘﺩ ﻫﺫﻩ ﺍﻟﻤﻭﺍﺩ ﺒﺎﻟﺘﺠﻔﻴﻑ ﻓﺎﻥ ﺃﻓﺭﺍﺩ ﺍﻟﺠﺭﺍﺩ ﺘﻔﻀﻠﻬﺎ ﻋﻠﻰ ﺍﻟﻨﻭﻋﻴﻥ ﺍﻟﺴﺎﺒﻘﻴﻥ‪.‬‬
‫ﻜﺫﻟﻙ ﻴﻤﻜﻥ ﺍﻟﻘﻭل ﺒﺎﻥ ﻫﻨﺎﻟﻙ ﺒﻌﺽ ﺍﻟﻤﻭﺍﺩ ﺍﻟﺠﺎﺫﺒﺔ ﻓﻲ ﺍﻟﻨﻭﻋﻴﻥ ‪H. ovalifolium,‬‬
‫‪H arabianense‬‬
‫ﺘﻔﻘﺩ ﺒﺎﻟﺘﺠﻔﻴﻑ ‪ .‬ﻭﺒﻬﺫﺍ ﻴﻤﻜﻥ ﺍﻻﺴﺘﻔﺎﺩﺓ ﻤﻥ ﺍﻟﻨﻭﻉ ‪ H.lignosum,‬ﻜﻤـﻭﺭﺩ ﻟﻤـﻭﺍﺩ‬
‫ﻁﺎﺭﺩﺓ ﺘﺴﺘﺨﺩﻡ ﻓﻲ ﻋﻤﻠﻴﺎﺕ ﺍﻟﻤﻜﺎﻓﺤﺔ‪.‬‬
‫ﻜﺫﻟﻙ ﻭﺠﺩ ﺃﻥ ﺍﻨﺠﺫﺍﺏ ﺃﻓﺭﺍﺩ ﺍﻟﺠﺭﺍﺩ ﻟﺭﺍﺌﺤﺔ ‪ H.lignosum‬ﻴﻜﻭﻥ ﺒﻁﻴﺌﺎ ‪ ،‬ﺤﻴـﺙ‬
‫ﺃﻨﻬﺎ ﺘﺄﺨﺫ ﻓﺘﺭﺓ ﺭﺍﺤﺔ ﻁﻭﻴﻠﺔ ﺜﻡ ﺒﻌﺩ ﺫﻟﻙ ﺘﺘﺭﺍﺠﻊ ﻭﺘﻐﻴﺭ ﺍﺘﺠﺎﻫﻬﺎ ﻤﺎﻋﺩﺍ ﺒﻌﺽ ﺍﻷﻓﺭﺍﺩ‬
‫ﺍﻟﺘﻲ ﺘﻤﻜﻨﺕ ﺃﻭ ﻗﺎﺭﺒﺕ ﻤﻥ ﺍﻟﻭﺼﻭل ﻟﻠﻨﺒﺎﺕ ﻭﻟﻜﻥ ﺩﻭﻥ ﺘﻐﺫﻴﺘﻬﺎ ﻋﻠﻴﻪ‪ .‬ﺒﻴﻨﻤﺎ ﺍﻻﻨﺠﺫﺍﺏ‬
‫ﻜﺎﻥ ﻭﺍﻀﺤﺎ ﻟﻠﻨﻭﻋﻴﻥ ﺍﻵﺨﺭﻴﻥ‪ ،‬ﺤﻴﺙ ﺘﻤﻜﻨﺕ ﺍﻷﻓﺭﺍﺩ ﻤﻥ ﺍﻟﻭﺼﻭل ﻟﻠﻨﺒﺎﺕ ﻓﻲ ﻓﺘـﺭﺓ‬
‫ﺯﻤﻨﻴﺔ ﻭﺠﻴﺯﺓ‪ .‬ﺃﻤﺎ ﺴﻠﻭﻜﻴﺎﺕ ﺍﻷﻓﺭﺍﺩ ﻤﻥ ﺘﺤﺭﻴﻙ ﻗﺭﻭﻥ ﺍﻻﺴﺘﺸﻌﺎﺭ ﻭﺍﻟﺤﺭﻜـﺔ ﻓـﻲ‬
‫ﺍﺘﺠﺎﻫﺎﺕ ﻤﺨﺘﻠﻔﺔ ‪ ،‬ﻻ ﻴﻭﺠﺩ ﺍﺨﺘﻼﻑ ﻜﺒﻴﺭ ﺒﻴﻥ ﺍﻟﺜﻼﺜﺔ ﺃﻨﻭﺍﻉ‪.‬‬
‫ﻤﻥ ﻫﺫﻩ ﺍﻟﺩﺭﺍﺴﺔ ﻴﺘﻀﺢ ﺃﻥ ﺍﻟﻨﻭﻋﻴﻥ ‪ H. ovalifolium, H arabianense‬ﻤـﻥ‬
‫ﺃﻫﻡ ﺍﻷﻨﻭﺍﻉ ﺍﻟﺘﻲ ﻴﻤﻜﻥ ﺍﻻﺴﺘﻔﺎﺩﺓ ﻤﻨﻬﺎ ﻓﻲ ﺇﺠﺭﺍﺀ ﻋﻤﻠﻴﺔ ﺍﻟﻤﺴﺢ ﻟﻠﺠﺭﺍﺩ‪ .‬ﻭﻫﺫﺍ ﻴﺅﺩﻱ‬
‫ﻟﺘﻭﻓﻴﺭ ﺍﻟﻭﻗﺕ ﻭﺍﻟﺠﻬﺩ ﺒﺼﻭﺭﺓ ﻜﺒﻴﺭﺓ‪ .‬ﻜﻤﺎ ﺃﻥ ﺘﻭﺍﺠﺩ ﻫﺫﻩ ﺍﻷﻨﻭﺍﻉ ﻭﺍﻨﺘﺸﺎﺭﻫﺎ ﺒﺼﻭﺭﺓ‬
‫ﻭﺍﺴﻌﺔ ﻴﻌﺩ ﺴﺒﺒﺎ ﻭﺍﻀﺤﺎ ﻟﺘﻭﻗﻊ ﺇﻤﻜﺎﻨﻴﺔ ﺤﺩﻭﺙ ﺍﻟﻁﻭﺭ ﺍﻟﺠﻤـﺎﻋﻲ ﻭﺒﺎﻟﺘـﺎﻟﻲ ﺘﻜـﻭﻥ‬
‫ﺍﻷﺴﺭﺍﺏ‪ .‬ﻭﺫﻟﻙ ﻴﺴﺎﻋﺩ ﻓﻲ ﻭﻀﻊ ﺍﻟﺘﺩﺍﺒﻴﺭ ﺍﻟﻼﺯﻤﺔ ﻟﻠﻭﻗﺎﻴﺔ ﻤﻨﻬﺎ‪ .‬ﻜﻤﺎ ﻴﻤﻜﻥ ﺍﺴﺘﺨﺩﺍﻡ‬
‫ﺍﻟﻨﻭﻋﻴﻥ ﺍﻷﻭﻟﻴﻥ ﻜﻤﻭﺍﺩ ﺠﺎﺫﺒﺔ ﻓﻲ ﻋﻤﻠﻴﺎﺕ ﺍﻟﻤﻜﺎﻓﺤﺔ ﻋﻥ ﻁﺭﻴـﻕ ﺍﻟﻁﻌـﻭﻡ ﺍﻟـﺴﺎﻤﺔ‬
‫ﻭﺍﺴﺘﺨﺩﺍﻡ ﺍﻟﻨﻭﻉ ﺍﻟﺜﺎﻟﺙ ﻜﻤﻭﺭﺩ ﻟﻠﻤﻭﺍﺩ ﺍﻟﻁﺎﺭﺩﺓ‪.‬‬
INTRODCUTION
Locusts belong to a large group of insects commonly called grass
hoppers which belong to the super family Acridoidea, and the most
important locusts are all in the family Acrididae (ALRC, ١٩٦٦.)
The locusts are counted among the major pests in the Sahel zone of
Africa.The desert locust, Schistocerca gregaria (Forskål), is one of the
oldest insects known in history. Today, the desert locust is still occupying
the whole of Arab world north Africa from west to east, including the
Arabian peninsula, northern India, and southern central Asia. During the
major plagues, the invasion area covers about ٢٩ million kilometres
square, which is equivalent to one fifth of the earth surface. During the
recession periods, the desert locust activities concentrate in the arid and
semi arid areas covering about ١٦ million Km² (Meinzingen, ١٩٩٣). The
desert locust has inflicted incredible losses, both in terms of money and
crops to most of the countries it has invaded. One ton of Locusts (a very
small part of an average swarm) eats much food in one day as ١٠ elephants
or ٢٥ camels or ٢٥٠ people. (ALRC, ١٩٦٦). During (١٩٨٦-١٩٨٩), a desert
locust plague occurred requiring mobilization of resources costing some
US$ ٣٠٠ million and the application of some ١٥ million litters of pesticides
over more than ١٧ million hectares In ١٩٩٢-١٩٩٤ yet another major
upsurge occurred and about US$ ٤٥million was spent on chemical control
over an area of ٤ million hectare. (Eltigani, ١٩٩٦).
The most important feature of the desert locust is its ability to
interconvert between two morphologically, physiologically and
behaviourally distinct phases, the solitaria and the gregaria. During the
solitarious phase, which is characterized by low population densities, the
insect lives in areas that are not, or only minimally, used for agriculture.
These so called recession areas, which have an average annual
precipitation of no more than ٢٠٠ mm, are distributed across several Sahel
countries. The solitarious phase the Desert Locust does not venture out of
its original habitat. It is integrated into the food chain, constituting a useful
component of the biotope. It does not have any injurious effect on
agricultural production there (Herok, ١٩٩٥).
The importance of solitary phase stems from its transformation
from the solitarious to the gregarious phase. This is induced by a complex
system of changing environmental conditions that has not yet been fully
illuminated (Chandra, ١٩٩٠). The major locust out breaks are generally
associated with improved rains and vegetation after a relatively long dry –
weather spell. They begin with the migration of solitary – living locusts into
areas where sufficient rain has recently fallen. Mating and egg – laying
then occur. A sequence of appropriately timed rains in the winter and
summer breeding areas, coinciding with the appearance of a new locust
generations, may lead to high concentration and multiplication rates of the
insect, which are then accompanied by gregarisation and swarming
(Hassanali and Mahamat, ١٩٩١).
Johnston (١٩٢٦) discovered in February ١٩٢٦ that the Red Sea
coast of the Sudan was an area where S. gregaria could transform from the
solitary to the gregarious phase. The Red Sea area is one of the habitats of
solitary locusts. It is one of semi – permanent convergence of winter and
comes under the influence of the Inter – Tropical Convergence Zone in
summer. Most rains in the Red Sea area occur in winter, but there is also
some rainfall in summer, in the south more than in the north. The
prolonged rainfall in the south is probably one reason why the Red Sea
coastal areas have locust populations very frequently. It is also rich with
different species of desert plants, such as Heliotropium spp, Diptergim spp
and Aerva spp.
The Desert Locust is polyphagous (Evans and Bell, ١٩٧٩),
especially in the gregarious phase. However, solitarious populations in semi
– arid habitats have a limited choice of food plants (Kennedy ١٩٦٢).
Despite the polyphagous nature of the species a hierarchy of preference
exists. Some plants are preferred for sheltering and oviposition, like
Heliotropium and Millet (El Bashir and Abd El Rahman, ١٩٩١; Bashir and
Abd El Rahman, ICIPE report ١٩٩٥; Bashir, et al., ٢٠٠٠). The biology of
locust is influenced by the type of food available in nature (Rao, ١٩٤٢ and
١٩٦٠; Uvarov, ١٩٦٦; Bhatia and A hlwalia, ١٩٦٧ and Ibrahim, ١٩٧٢)
Recently, interest in the feeding activities has been prompted by
the desire to understand the basic processes of host – plant selection by
grasshoppers, and through this understanding to bring about more
effective methods of crop and rangeland protection.
Some of the plants with which solitarious Desert Locust are often
associated in the Red Sea area are Heliotropium spp. Since the Red Sea
area has been identified as one of the concentration areas where many
workers in the Desert Locust problem feel that preventive control or
upsurge suppression should be focused on (Van Huis ١٩٩٤), it will be very
important to know the effect of the preferred host plants (Heliotropium
spp) on the life system of the solitary Desert Locust.
This study investigates the effect of (Heliotropium ovalifolium,
Heliotropium lignosum and Heliotropium arabianense) on the life system of
the solitary Desert Locust. There are more than six species of Heliotropium
in the Red Sea area, but these three species are found frequently in the
locust habitat. An advantage of this type of testing is that it is possible to
know the preferred species, which will make the survey more limited
because the surveyor only has to look for the common species. This will
save a lot of money, effort and time. Also it helps to suggest and detect any
gregarisation, which may happen. The locust must be controlled before
they come together because it may be too late to stop the damage once they
swarm and migrate.
LITERATURE REVIEW
١ Host plant (Heliotropium spp)
Heliotropium spp are herb or shrub plants. The flowers are yellow white,
small, in leafless (at least in the upper part) scorpionid inflorescence, often ١sided cumes. Calyx ٥-parted, either persistent or deciduous with the fruit; corolla
funnel shaped or salver – shaped with ٥-lobed limb. Style simple, terminal
inserted on the top of the ovary. Stigma with broad base surrounded by a fleshy
rim ovary at maturity breaking up into ٤ distinct drouplet, these rarely connate in
pairs (Migahid, ١٩٧٨).
Heliotropim ovalifolium Forsk. Agrey – hispid annual, herbaceous from a
frutescent base, with elliptical-lanceolate, long petiole leaves and minute,
bracteate flowers in narrow cymes, gets blackish-grey when dry.
Heliotropium arbianense Fres (Hassan, ١٩٧٤), is prostrate, erect greenish white
shrub lets, ٢٠ – ٤٠ cm. Stem hairy, leaves alternate, ovate-oblong densely hairy ١١٫٥cm long to a petiole leaf -apex acutish and margin wavy. Cymes ٥-١٠cm long,
corolla ٨mm long, nearly twice as long as calyx flowers white. Nut lets four in
number. Reported in Red Sea area between sea level and ٤٠٠٠ft. (Hassan, ١٩٧٤;
Migahid, ١٩٧٨).
Heliotropium lignosum Schweinf. Ex Bunge: Fruticose shrubby plant with short,
woody ascending stems, densely clothed with whitish hairs. Leaves small, sessile,
lanceolate, with short revolute margin, and densely and shortly bristly on both
surfaces. Spikes short, dense, ٣-٦-flowered. Nut lets hispid (Migahid, ١٩٧٨).
٢ The locust
٢. ١ Identification
According to COPR (١٩٨٢), Uvarov and Launois explain that Schistocerca
gregaria (Forskål ١٧٧٥) has prosternal tubercle straight, blunt and slightly
inclined backwards. Male subgenital plate bilobate, cerciflat and blunt. Tegmina
marked with large irregular spots. Pronotum not crested, more constricted and
saddle-Shaped in the gregarious phase. Adult coloration in the solitarious phase is
sandy, gray or brownish, often with light. Coloured median stripe on pronotum.
On the other hand the immature gregarious phase are pink, and the mature ones
are bright yellow.
٢. ٢ Desert Locust Classification
Schistocerca gregaria belongs to the sub family Acridnae of family
Acrididea. Family Acrididea belong to the sub order Callifera of the order
Orthoptera. Seven species are identified in the genus Schistocerca one of them is
gregaria. The species gregaria has two sub species, gregaria (Forskål) and
flaviwentris (Paster and Smolikowski, ١٩٨٩).
٢. ٣ Distribution
The invasion areas of Schistoceca gregaria include mainly the semi desert
and short grass Savannah, and is capable of invading the whole of N. Africa,
Southern and western parts of Iberian Peninsula, Sardinia, the Azores, Madeira,
Canary Is., Capverde Is., W.Africa, North of Equatorial, rain forest east words to
N. E. Zaire and to S.Tanzania on the Indian Ocean, the Arabian Peninsula,
Socotra, the middle east north to E.Turkey, Cyprus, the southern republics of the
USSR, Iran, Afghanistan, the Indian sub-continent south to ١٠° N and east to the
Burmes border (Régniér,١٩٣١). In the Sudan, Schistocerca gregaria has been
recorded from the Red Sea littoral and along the central parts of the country. The
Sudan lies at the heart of both the invasion and recession areas. It is mainly a
summer breeding area, though breeding may take place in winter at the Red Sea
littoral. However the country is subjected to infestation as far south as latitude
١٢° N (Maxwell-Darling, ١٩٣٦; Walloff, ١٩٦٦; Shumtterer, ١٩٦٩ and Karar,
١٩٧٢).
According to COPR (١٩٨٢), Holst, Uvarov, Waloff, Rainey , Weidner, Dirsh and
Krauss mentioned that the Desert locust has been recorded in the E. Atlantic, St
Helena, British Is., possibly Denmark, Mediterranean region (Yugoslavia,
Greece), Red Sea, Gulf of Aden, Arabia sea, Persian Gulf and Mozambique. Also
there are records of individuals carried by ships from Madagascar to Srilanka
and Australia.
٢. ٤ Locust Habitats
On locust habitats according to Mulkern (١٩٦٦), a number of investigators
found that distribution was related to vegetation composition as movement of
individuals was much less in areas of favorable host plants than in area of un
favorable host plants.
The Red Sea region is mainly a winter breeding area, but spring breeding is
believed to take place on the mountain range and summer breeding on the western
slopes and plains descending from the plateau twoards the hinterland. The area is
part of the central region considered as the primary source of up surges and
potential plagues.
The variety of host plants available for any species of grasshopper is limited
because their restriction to distinctive habitats with associated vegetation has long
been established (Cantrall, ١٩٤٣; Baccetti, ١٩٦٣). According to Mulkern, ١٩٦٦
many investigators came to the conclusion that food selection was primarily the
consequence of habitat selection. The same author mentioned that distribution was
related to vegetation composition as movement of individuals was much less in
area of favorable host plants He suggested that this factor accounted for the
concentration of grasshopper species in the favorable area. Anderson (١٩٦٤), also
concluded that vegetation had definite influence on distribution as grasshoppers
were never found in areas which did not include preferred host plants and the
occupancy of this area was influenced by the physical structure of the vegetation.
٢. ٤. ١ Habitats of Solitarious Desert Locust
Solitarious locusts live in fewer varieties of habitats than gregarious
swarms. In general they occur in open sandy steppes with fewer or no trees. They
are not usually present in places where the trees are on average less than ١٠ m
apart. The vegetation generally consists of perennial bushes and herbs less than a
meter high and annual plants which come up after rain. The habitats of solitarious
locusts in the different regions are Pakistan, Iran and India (during summer)
where the main food is Tribulus alatus and Aerva persica. In the rainy season
parts of southern Arabia become suitable habitats for Desert Locust. Small
concentrations can be found in patches of such plants as Chrozophora
oblongifolia, Tribulus sp, Dipterygium glaucum and Aerva persica. The southern
Red Sea area is one of semi- permanent convergence of winds in winter and
comes under the influence of the ITCZ (Inter- Tropical Convergence Zone) in
summer. This habitat is always cultivated with Pennisetum (dukhn). Also there
are many plants like Heliotropium and Diptergium. In West Africa the Locust
habitats are associated with the Saharan high lands and with the open steppes
surrounding the Sahara. Schouwia thebaica, Tribullus alatus and Hyoscyamus
muticus grow in this habitat (Steedman, ١٩٨٨).
٢. ٥ Economic importance
Desert locust hoppers eat about their own weight of fresh vegetation each
day, the amount increases from about ٢٠mg at the beginning of the first instar to
about ١٫٥ g in the middle of the fifth instar (COPR, ١٩٨٢). Migrating immature
adults need to eat at least their own weight (٢-٣g) of fresh vegetation each day,
and possibly three times as much (Weis-Fogh, ١٩٥٢). Desert Locusts feed on a
very wide range of plants. They also inflict considerable damage by actually
feeding, and breaking branches with their weight when densely settled. Because
swarms are so mobile there is great variation in the amount of damage caused
seasonally, from country to country and from region to region. The greatest
recorded crop losses occur when young migrating swarms of immature adults
reach cultivated areas. Examples of crop losses caused by Desert Locust in Libya
in ١٩٤٤ were ٧٫٠٠٠٫٠٠٠ tones grapevines/; ١٩٪ of total vine cultivated (ALRC,
١٩٦٦). In the Sudan according to ALRC (١٩٦٦), the value of losses was £
٣٩٠،٠٠٠ in ١٩٤٤ and ٥٥،٠٠٠ tons of grain in ١٩٥٤. An area of ٣٫٧ million
hectare were infested during ١٩٨٨ plague (Abass and Barsi, ١٩٩١). Also for the ٩year period ١٩٤٩-١٩٥٧ the FAO estimate of the total value of crop damage in ١٢
invaded countries was £ ١٥ million (FAO ١٩٥٨). During ١٩٨٦-١٩٨٩ a desert
locust plaque occurred and required mobilization of resources costing some US $
٣٠٠ million and the application of some ١٥ million litters of pesticides over more
than ١٧ million hectares some of which were in ecologically sensitive areas. In
١٩٩٢-١٩٩٤ yet another major upsurge occurred and about US $٤٥ million was
spend on chemical control over an area of ٤ million hectares. Also swarms were
reported in the central region in Saudi Arabia, Somalia, Mali, Mauritania, Chad,
Sudan and Eritrea in ١٩٩٥ (Eltigani, ١٩٩٦).
٢. ٦ Life Cycle
The life cycle comprises three stages, egg, hopper and adult. Immature
adults may become sexually mature in few weeks or few months, according to
environmental conditions. The incidence of maturation can be recognized by the
disappearance of the pink colour from the hind tibia (Steedman ١٩٩٠). Males
mature before females, but oviposition usually commences within about ٢days of
copulation. Copulation some times occurs with female which appear not to be
fully mature, that is, females in which the eggs are not fully developed. Once eggs
are fully developed in side, the female can only keep them for about ٣days; then
they may be oviposited. (Steedman, ١٩٩٠).
Husain and Ahmed (١٩٣٦) recorded that a single female lays ٩ egg pods in the
laboratory; while Hunter –Jones (١٩٥٨) reported an instance of ٢٥ pods laid by
one female in the laboratory. On the other side according to Eltigani (١٩٩٦)
Ripper and George, found that females lay an average of ٣ egg pods at an average
interval of one week, minimum ٣ days maximum about ١٤ days.
The numbers of eggs in pods of locust in swarms vary from ٢٠-to over
١٠٠. (Steedman, ١٩٩٠). However Ashall and Ellis (١٩٦٢), reported
that the number of eggs per pod ranged from ٣٦ to ١٢٨. Females
reared in the laboratory may lay from ١٠ to ١٤٠ eggs per pod
(Norries, ١٩٥٢). On the other hand, Meinzingen (١٩٩٣) explained
that solitary female mostley lays ٣ – ٤ pods, each pod containing
١٠٠ – ١٦٠ eggs, with egg pods laid at interval of ٧ – ١٠ days while
gregarious female usually laid ٢ – ٣ egg pods each with about ٦٠ –
٨٠ eggs. Hunter- Jones (١٩٦٦), Uvarov (١٩٦٦), Waloff (١٩٦٦) and
Wardhugh, et al., (١٩٦٩), mentioned that provided there is
adequate soil moisture the rate at which eggs develop varies
according to the soil temperature. Steedman (١٩٩٠) and
Meinzingen (١٩٩٣) recorded that the egg incubation period ranges
١٢-٢١ days depending on the temperature. The period for
development decreases from about ٧٠ days to ١٠-١٢ days, when the
temperature ranged between ١٥°C to ٣٥°C; above ٣٥°C the period
no longer decreases and high mortality occurs (COPR, ١٩٨٢).
Moulting usually occurs five times during the development of the
gregarious desert locust and five or six in solitarious individuals.
The extra instars occurring between the third and the fourth. Each
moult is indicated by a marked stripe on the eye. The rate of
development depends on temperature. It varies from about ٢٢days
under ‘hot’ conditions to over ٧٠ days under ‘cool’ condition
(COPR, ١٩٨٢). The first, second, third fourth and fifth instar
weights are ٣٠-٤٠, ٥٠-٨٠, ١٢٠-٢٠٠, ٥٠٠-٧٠٠ and ١٠٠٠ ١٢٠٠ mg r
respectively. Also the developmental periods are ٥-٧, ٦-٨, ٧-٩, ٧-٩
and ٩-١٢ days respectively (Steedman, ١٩٩٠).
The length of life of individual adults varies. Some have been kept alive in cages
for over a year, but in the field they probably life between ٢٫٥ and ٥ months.
Apart from accidental death the live span depends on how long they take to
become sexually mature. The quicker they mature the shorter the total length of
life (Steedman, ١٩٨٨).
According to Eltigani (١٩٩٦), King, Uvarov and Bodenheimer were of the
opinion that generally the desert locust has only one generation in the year, with a
long diapause in the adult stage. While Ballard, et al., (١٩٣٢) was of the opinion
that under favorable natural condition, there might be three generation in one
year.
٢-٧ Behaviour
Locusts are characterized by their ability to transform reversibly in a
graded manner between two extreme phases, solitaria and gregaria, that differ in
physiology, biochemistry, behaviour, pigmentation and morphology (Uvarov,
١٩٦٦).
The Desert Locust Schistocerca gregaria is the race most sensitive to changes in
population transformation from the solitarious to the gregarious phase and vice
versa. This occurs rapidly and frequently (COPR, ١٩٨٢). In the solitarious phase,
population densities can be extremely low (Uvarov, ١٩٧٧) and although patchy
distribution of host plants may contribute to bringing the insects together,
successful mate finding may depend on long – rang pheromone signals (Byer,
١٩٩١ and Hassanali and Mahamat, ١٩٩١). Rainey (١٩٦٢), Roffey and Popov,
(١٩٦٨) and Uvarov, (١٩٧٧), mentioned that gregarisation is predicated on locust
density which may be promoted by a variety of environmental and biotic factors,
including covergent winds, habitat topologies, improved rains and distribution of
food plants and oviposition sites. Some phase related traits, such as agregation
behaviour (Roessingh and Simpson, ١٩٩٤ and Bouarchi et al., ١٩٩٥) and
emission of the mediating aggregation pheromones (Torto et al., ١٩٩٤ and ١٩٩٦
and Deng et al., ١٩٩٦), change rapidly with density, others, such as
morphometrics, take several generations (Pener, ١٩٩١ and Deng et al., ١٩٩٦).
Bouarchi et al., (١٩٩٦) revealed that habitat microstructures, such as patchy
distribution of food plants and perching sites, facilitated the concentration of and
encounter between other wise reluctant desert locust solitarious hoppers. In time,
this leads to active cohesive behaviour. This was consistent with the work of
Deng et al., (١٩٩٦) which demonstrated that forced crowding of solitaria led to
rapid production of the gregarious-phase aggregation pheromone.
٢. ٨ Host plant
The Desert Locust is polyphagous, especially in the gregarious phase
(Evan and Bell, ١٩٧٩). However, solitarious populations in semi arid habitats
have limited choice of food plants (Kennedy, ١٩٦٢). Despite the polyphagous
nature of the species, hierarchy of preferred host plants exists. Some plants are
preferred for shelter, to oviposite close to, e.g. Heliotroium and millet (ElBashir
and Abdel Rahaman ١٩٩١;Bashir and Abdel Rahaman, ICIPE report, ١٩٩٥). Also
Bashir et al (٢٠٠٠) recorded that during the successive seasons and early during
the rainy season, the incoming solitarious females, oviposited predominantly in
the vicinity of Heliotropium species and millet seedlings. Solitarious nymphs also
preferred to feed on these plants. More than six species of Heliotropium occur in
the various habitats of the desert locust in the Red Sea Area. It appears that the
Heliotropium in the eastern parts of the Central Zone takes the role that Shouwia
pupurea (Forsk.) plays in West Africa (Ghaout, et al., ١٩٩١).
٢٫٨٫١ Host finding
According to Uvarov (١٩٧٧), relative amount of grass and other plants in the
crop of Schistocerca hoppers was correlated with the abundance of various plants
in the habitat. Abundance being expressed in terms of the diameters of the plants.
The finding of acceptable food is affected by the general behaviour pattern. For
example species living mainly on the ground are more likely to feed on low plants
and plant debris .The daily behaviour pattern also affects feeding, visual
attraction, colour and olfactory orientation by the specific smell of particular
plant, are of importance for locating the food.
The attraction of Schistocerca hoppers by the smell of food plants was
mentioned by Volkonsky (١٩٤٢), but without sufficient details. Experiments by
Haskell et al., (١٩٦٢) in a wind tunnel proved that an air current carrying the
smell of crushed grass and of a variety of odorous substances caused Schistocerca
hoppers, which had been starved for ٢٤ hours and walking down wind, to reverse
their direction and walk twoards the source of the odorous. This response was
shown at a distance of some ٦٠ Cm. Williams (١٩٥٤), obtained no evidence of
olfactory attraction in Locusta hoppers, but his experiments were inadequate for
definite conclusion. Dadd (١٩٦٣) suggested that fourth - instar hoppers and adults
of Schistocerca may be more able to follow odour signals than young hoppers. On
the whole, if attraction to the smell of food plants exists, there is still very little
evidence of its effective range and on this depends its influence on food selection
in the field.
Uvarov, (١٩٧٧) mentioned that once the insect is on a plant, the chemical
properties of the latter appear to be examined by the antenna and palps repeatedly
touching the plant. Following an examination of a plant by the palps, the insect
usually takes a small bite, which is chewed, and then feeding because either
continues or the insect moves away. According to Uvarov (١٩٧٧) Thomas
suggests that the final selection is a matter of taste discrimination by the sensilla
on the mouth –parts. Those plants, which are only nibbled, but not eaten, are
rejected for their taste on chemical grounds. A well-known example is the tree
Azadirachta indica that is unpalatable to Schistocerca (Rao, ١٩٦٠; Roonwal,
١٩٥٣). Another example of taste being responsible for the rejection of a normally
favourite food-plant is that of Schistocerca hoppers refusing to eat Heliotropium
undulatum after it had been dipped in ٥٪ salt solution for a minute and then dried
(Rao ١٩٦٠).
Refusal to feed on a plant after biting it, or its acceptance, led to the theory
that this depended on the presence or absence of some specific substances termed
phagostimulants (Goodhue, ١٩٦٣). An alternative view is that acceptance is
affected by the presence of some nutrient substances, while rejection may be due
to specifically repellent ones (Dadd, ١٩٦٣; Thorsteinson, ١٩٦٠).
٢-٨-٢ Factors in food selection
The water content of plants is often regarded as affecting the selection.
Williams (١٩٥٤), found that fresh grass (Holcus lanatus) was consumed more
than dry one when both were offered in the same cage. While Isely (١٩٤٦)
recorded that grasshoppers of dry habitats refused more succulent grasses in
favour of the drier ones. Kaufman (١٩٦٥) also found similar preference for drier
grasses in grasshopper from humid habitats.
The chemical composition of plants may have major influence on
selectivity by grasshoppers .The reception of chemical stimuli over distance or
more than few centimeters is generally considered doubtful although
experimentation in this regard is far from exhaustive (Dadd, ١٩٦٣).
Plant volatiles play a significant role as cues in host selection by
phytophagous insects. One group of host plant volatiles widely studied are the
‘green leaf volatiles` (GLVs) which are aldhydes and esters released when plant
tissues are damaged either mechanically or by herbivory (Visser and Ave, ١٩٧٨;
Visser, et al., ١٩٧٩; Dikens, et al.,١٩٩٣ and Light, et al., ١٩٩٣). Host plant
recognition by grasshoppers has been examined in few studies. Air borne odours
from damaged cabbage and damaged grass have been demonstrated to be
attractive to the desert locust Schistocerca gregaria
(Haskell, et al., ١٩٦٢;
Kennedy and Moorhouse, ١٩٦٩ and Moorhouse ١٩٧١). Najagi and Torto, (١٩٩٦)
found that nymphs of S. gregaria, generalist feeder, detect abroad range of GLVs
in the volatiles of its host plants. However, quantitative and qualitative differences
in components of the volatiles and previous exposure of the insects to the volatiles
may affect their preference hierarchy for host plants in the field. It remains to be
investigated what role these chemicals play in the host selection behaviour of
nymphs and adults of the desert locust.
No record of color being of important in attractive patterns has been made
(Hjelle,١٩٦٤). Mulkern (١٩٦٦) in some preliminary trials found that grasshoppers
would choose diet preparations containing commercially obtained chlorophyll
powder over an identical diet without chlorophyll. It was not determined
definitely whether the preference was due to the green color or to
chemostimulation from chlorophyll. Dadd (١٩٦٠) reported that chlorophyll is not
more effective than distilled water as a phagostimulant.
The physical composition of plants texture, pubescence, turgidity, manner
of growth, undoubtedly play an important part in food selection. The primary
effect of the physical structure seems to be to modify feeding once the plant has
been reached, although size or manner of growth may influence visual attraction.
Many physical structures of plants have been mentioned as deterrents to feeding
(Chapman, ١٩٥٧).
٢. ٨. ٣ Effect of food on the biology
The biology of the locust is influenced by the type of food available to the
insect in nature (Pfadt, ١٩٤٩; Rao, ١٩٤٢ and ١٩٦٠; Uvarov, ١٩٦٦; Bhatia and
Ahlualia, ١٩٦٧ and Ibrahim, ١٩٧٢). Eltigani (١٩٩٦) recorded that under
laboratory conditions, food plants have marked different effects on development,
weight gain, survival, maturation, fertility, fecundity and longevity. According to
him six plant species, Launaea capitata, Heliotropium undulatum, Pennisetum
typhoideum,
Crotalaria
microphyla,
Dipteryinm
glauaum
and
Tribulus
longipetallus, indused rapid growth and enhanced nymphal development, with
closely synchronized moulting. It has been shown in several studies that food
quality and quantity also influence insect reproduction (Jackson, et al., ١٩٧٨ and
Injeyan et al., ١٩٨١).
Rao (١٩٦٠) recorded that Schistocerca gregaria has different rates of
development when fed on different stages of growth of the same plant. While
Wardhugh et al., (١٩٦٩) showed that the development rates of S. gregaria in
outdoor field cages were not significantly different when fed on eight different
diets (millet, lucern, sorghum, and arafag). He investigated the incubation period
of the desert locust under various conditions typical of the Tiahama and Hijaz of
Saudi Arabia and found no significant difference between the development rates
of hoppers fed on different species of plant. Though the result did suggest that
hoppers reared on either barley or Sorghum required longer period to fledge than
those reared on either millet or lucern.
Also Rao (١٩٦٠) found that with the desert locust, Tribulus terresteis allowed
rapid maturation while Panicum delayed it. Although the Sorghum provided to
desert locust was not senescent, it seemed probable that some other factor delayed
maturation.
According to Mulkern (١٩٦٦), Stolyarov, and Waloff found S. gregaria
survive better on some plants than on others. And Ellis, et al., (١٩٦٥), reported
that the sexual maturity and moulting of S.gregaria was influenced by
monoterpenoids and hormones from food plants. Variation in these substances in
plants controlled the seasonal development of grasshopper.
Water extract of plants was found to be essential to synthetic diets for
complete development of several species of grasshoppers. However, there are
striking differences among extracts from different plant species in their ability to
promote growth and survival when incorporated into otherwise similar diet
preparations (Mulkern, ١٩٦٦).
Toy (١٩٧٣) investigated the effect of food on the development of the desert
locust. He found that, the rate of development, mortality, feeding activity of
nymphs and morphometrics of adults were more successful when reared on
grasses (Agropron repens and Poa annua), than on other plant species like lime
privet and spinach. The former (A.repens) gave well-fed mature adult, while the
latter (spinach, Spinacia oleracea) gave brachypterous adults.
Ba-Angood (١٩٧٤) found that the hopper development of S. gregaria at ٢٥-٣٢C°
was ٣٢٫٧± ١٫٣٠ days on Pennisetum typhoideum Rich. It was ٢٧٫٩±٠٫٩٨ days on
Sorgum vulgare pers. (Dura), ٣٥٫٨±٠٫٣٥ days on Medicago sativa L. (Berseem),
٣١٫٦±٠٫٣٥ days on mixed food (Cotton, Dura, and Berseem), it was٢٩٫٥± ٠٫٢٥
days. The highest survival percentage up to the adult stage was on mixed food
reaching ٦٢٪, followed by ٥٨ % on Sorgum vulgare, and ٥٤٪ on Pensoutem
typhodium. ٣٢ % ٠n Medicago sataiva and ١٦٪ on Gosspium barbadense. A
marked high rate mortality was observed in the first hopper stage for those insects
reared on Cotton and Berseem.
According to Jackson et al., (١٩٧٨) food plants have markedly different effects on
growth and development of the desert locust. P typhodeum, Dipterygium glacum,
Tribulus longipetalus (plus T. terrestris) and (Chrozophora oblonifolia) support
rapid growth and development. A pure diet of Sorghum sp, allows some hoppers
to reach the adult stage in a normal period. But many are retarded. In general
Pennisetum or Sorghum tended to enhance gregarious characteristics, while
Dipterygium accentuated solitarious characteristics. They also reported that the
reproductive capacity of these insects impaired by mono specific diet, even when
it is adequate for non- reproductive growth.
Bashir and Abdel Rahaman (ICIPE (International Center Of Insect Physiology
and Ecology) report, ١٩٩٥) recorded that the solitarious nymphs under laboratory
conditions attain sufficient weight and survive to fledgling stage on fewer plant
species compared with gregaria. However, compilation and analysis of life tables
data for solitaria was possible on still less number of plant species. In addition to
being food source, plants play other roles in the life system of Desert Locust.
Some plant species trigger the maturation process and many enhance
gregarisation
(Carlisle, et al., ١٩٦٥) while others inhibited gregarisation
(Guichard, ١٩٥٥).
In a study to evaluate the effect of moist air with fresh food, and dry air
with dry food on phase characteristics Jackson, et al., (١٩٧٨) studied the effect of
seven natural food plants on the phase status of the desert locust, and monitored
changes in colour, morphometrics number of eye stripes and fecundity. Their
result revealed that pennisetum typhoideum (Burm.f.) and Sorghum bicolor
enhanced gregarious characteristics, while Dipterygium glaucum (oecn)
accentuated solitary traits.
MATERIALS AND METHODS
The experimental food plants (Heliotropium spp) (plate ١ a, b,
plate ٢ a, b, plate ٣) used in the study were naturally growing plants.
They grew on seasonal rain fed flood plants, and standing near cultivated
plants. They were collected from Sallom area, ٣٠ km south west of Port
Sudan. Any part and age of the plants was used.
All experiment were conducted inside the laboratory and carried out
during ١٩٩٩ -٢٠٠١ seasons at the ICIPE field station in Port Sudan. The
laboratory temperature ranged between ٢٨٫٢ ºC maximum and ٢٥٫٢ ºC
minimum in summer, ٢٢٫٥ºC maximum and ١٨٫٥ºC minimum in winter.
The mean relative humidity was ٣٧٫٢ % in summer and ٦٠٫٥ % in winter
in season ١٩٩٩-٢٠٠٠.
Whereas the laboratory temperature ranged
between ٣٠٫٠ºC maximum and ٢٥٫٦ºC minimum in summer, ٢٢٫٨ºC
maximum and ٢٠٫٢ºC minimum in winter. The mean relative humidity
was ٤٠٫٥ in summer and ٦٩٫٣ % in winter in season ٢٠٠٠-٢٠٠١.
١ Effect of Heliotropium spp. on development, weight, maturation,
longevity, survival rate and feeding rate
The locusts used in the experiments were offspring of the solitary
stock bred at the ICIPE station.
Plate ١ a Heliotropium ovalifolium old plant.
Plate ١ b Heliotropium ovalifolium young plant.
Plate ٢ a Heliotropium arabianese, old plant.
Plate ٢ b Heliotropium arabianese, young plant.
Plat ٣ Heliotropium legnosum.
First instars nymphs were collected and kept together for ٤ days, and fed
on
a mixture of the three species of Heliotropium (H. arabianense, H.
ovalifolium and H. lignosum). The reason for keeping the hatchlings for
such a period before
the start of the experiment was that heavy mortality from natural causes
usually occurs in the first days. Any mortality occurring during this
period would have been unrelated to diet, and would have reduced the
size of the population available for the study. The nymphs were then kept
individually before starting the experiments because gregaraisation
behaviour would occur when they are kept together more than ٢٤ hours.
They were kept individually each in a separate cell of a ten-bank cage
(Isolated cage), (plate ٤) The cage has the following dimensions; (٦٠ x ٢٤
x ٣٠ cm), representing the length, width and height respectively (season
١٩٩٩-٢٠٠٠). In season ٢٠٠٠-٢٠٠١ they were kept individually each in a
separate cup (diameter, ١١٫٥ cm above and ٩٫٥ cm bottom), (plat ٥).
The number of nymphs reared on each species was ٣٠. Each cup or cell
containing the nymph was numbered. The tests on the three species were
started at the same time. Every day cells and cups were cleaned and the
uneaten food and faeces were removed and green fresh weighted food
was provided. The uneaten food and faeces were raped with aluminium
foil and put in the oven for ٢٤ hours at ٨٠ºC and weighted again to know
the consumption and assimilation of food according to the following
equation: Plate ٤. Solitary rearing bank cages (Season ١٩٩٩-٢٠٠٠).
Plate ٥. Solitary rearing cups (Season ٢٠٠٠-٢٠٠١).
In dry food = In wet food x Average dry weight / gm of each species.
Consumed dry food = In dry food – (dry spill + remaining dry food).
Consumed wet food = Consumed dry food x Average dry weight /gm
Assimilated dry food = Consumed dry food – Dry faeces.
At the same time observation on the locusts were carried out; dead
locusts, moulting dates successive nymphal moults and newly emerging
fledglings were recorded daily. Also locusts were weighted two days after
each moult using an electric digital sensitive balance. Maturation dates
were recorded, the sign of its occurrence is the yellowing of hind wings.
The dead locusts were recorded daily to enable computation of the
survival rate on the three species.
١. ٢ Effect of Heliotropium spp. on oviposition
The number of mature solitary locusts from experiment (١) was low,
therefore a new rearing was made to obtain ٢٣ pairs for each host plant
species tests. The solitary nymphs were reared as in (١) where ٦٠ insects
kept and fed on each species of Heliotropium. The date of maturation was
recorded. The mature adults were sexed and paired in special cages (١٠ x
١٠ x ٢٤ cm), (plat ٦ a, b). When mating was recorded, then each cell was
provided a metallic oviposition tube (size ١٢٫٥ x ٤٫٠ cm.), filled with
sand with ١٠٪ soil moisture. The tubes were examined daily for the
presence of egg pods and the tubes which contained egg pods were
replaced with fresh ones, labelled and incubated in the laboratory. The
Plate ٦ a, b Oviposition bank cages.
(b)
total number of eggs, number of hatched eggs, unhatched ones (fertile
and un fertile) and the incubation period were recorded and counted once
hatching
was
completed.
Also
the
preoviposition,
oviposition,
postoviposition period, fecundity, and longevity of the females were
recorded.
٢ Anti feeding experiments
٢. ١ Feeding on the three species of Heliotropium
Twenty (١٠ male, ١٠ female) fifth and six solitary instar nymphs
were fed on a mixture of fresh weighted plants of the three species of
Heliotropium. Each nymph was kept separately in cells of the rearing
cage ( plate ٤) and some in a small cage (٢٥ x ٢٥ x ٢٥) (plate ٧ a,b). The
uneaten food, spill and faeces were wrapped and placed in the oven at
٨٠ºC for ٢٤ hours and weighed to know the consumption from each
species. The tests were conducted with one set fed for ٢ days and
another set of ٢٠ nymphs fed for ٦ days until fledging.
٢. ٢ Feeding on filter paper impregnated with juices of Heliotropium
spp
The three species of Heliotropium were crushed separately using a mortar
and pestle. The juice of each species impregnated on filter paper was used
to examine antifeedant effect for ٢٤ hours on old fifth and sixth solitary
instar nymphs. Two sets of filter paper disks were used, one in a large
cage (wooden circular cage of ٩٨ cm diameter) (plate ٨ a, b) and the
other in a small cage (thick paper circular cage ٢٠ cm diameter) (plate ٩).
The filter papers used in the large cage were ١١ or
Plate ٧ a, b Small cage used in antifeedent experiment.
(a)
(b)
Plate ٨ a, b large cage used in antifeedant experiment using host plant
impregnated filter paper.
(a)
(b)
Plate ٩ Small cages used in antifeedant experiment using host plant
impregnated filter paper.
٩ cm in diameter while those used in the small cage were ٤٫٢٥ cm in
diameter (plate ١٠). The papers were given in a multiple-choice test to ten
nymphs (٥ males and ٥ females fifth and sixth instars mixed in the large
cage) starved for ٢٤ hours. The cages were heated and lightened by
electric bulbs. In the small cages males and females were put individually
each in a separate cage. The filter papers were fixed with pins in different
ways to facilitate group and paired testing. Three replicas were made in
the big and small cage and the distance between the papers was equal.
The test ended after ٢٤ hours. The eaten area from each paper was
measured using graph paper.
٢٫٣ Repellence experiment
Fifth and six instars nymphs (male and female) were put
individually in
a wind tunnel cage each side of which consist of
glass except the front one made of mosquito wire net (plate ١١). The
cage length (١٤٠-Cm) was sectioned and the sections were marked. A
fan was used to blow air through the wire mesh side into the cage. The
bottom of the cage is lined with sand. Seventy grams of tested host plant
species were used and placed at the ١٤٠ cm zone of the cage in front of
the fan. The insects each was released at the ٠٫٠ cm mark of the cage.
Resting, walking and other behaviour was recorded. The tests on each
plant species were replicated ٢٠ times.
٣ Data analysis
All data collected were subjected to analysis of variance (ANOVA)
and means were tested for significance using the Least Significant
Difference (LSD). Two variable means was tested using Independent ttest.
Plate ١٠ Filter paper impregnated with the juice of the three species of
Heliotropium.
A= H.ovalifolium, B= H. arabianense and C= H.lignosum.
Fig.١. Diagram of the flat-bed wind tunnel made of transparent glass; ١.
Exhaust fan;
٢. Heliotropium species; ٣. Doors for introduction and collection of
insects ;
٤. Ruler ١٤٠ cm long; ٥. Sliding glass door to release the test
insect; ٦. Wire mesh box;٧. Wind tunnel chamber; ٨. Insect test
pre-release compartment.
DISCUSSION
The results of various experiments revealed that two species of
Heliotropium (H. ovalifolium and H. arabianense) were suitable for
rearing and sustaining development of solitary nymphs, while the third
species namely H. lignosum was not. In season ١٩٩٩-٢٠٠٠ all nymphs
reared on H. lignosum died before reaching the ٤th instar. The duration
period of the ٣rd, ٤th and ٥th nymph instar periods were significantly long
on H. ovalifolium compared to H. arabianense. The ٢nd nymph instar
period was long on H. arabianense than H. ovalifolium and H. lignosum,
but it was not significantly different compared to H. lignosum. The ٦th
nymph instar period was long on H. arabianense, while the ٥th –fledgling
periods was long on H. oavlifolium. In case of the male, the ٤th and the ٦th
nymph instar periods were long on H. ovalifolium than on H. arabianense.
The ٣rd and ٥th-fledgling nymph period were significantly long on H.
ovalifolium compared to H. arabianense, while the ٢nd nymph instar period
was significantly long on H. arabianense. Female ٣rd, ٤th and ٥th nymph
instar periods were long on H. ovalifolium. In the ٢nd and ٦th instar the
period was significantly long compared to H. arabianense. The total
development period was not significantly different between the two
species (ovalifolium and arabianense) in season ١٩٩٩-٢٠٠٠. In season
٢٠٠٠-٢٠٠١ the nymph instar development period was significantly longer
in H. lignosum as compared to H. ovalifolium and H. arabianense. In case
of male and female ٢nd, ٤th, ٥th, and ٦th the nymph instar periods were
affected in the same manner. The ٢nd, ٤th and ٦th nymph instar periods were
significantly long on H. lignosum compared to H. ovalifolium and H.
arabianense. The ٥th nymph period was not significantly different between
the species. The male ٣rd instar period was also significantly longer on H.
lignosum as compared to the other two species. Also the ٥th to fledgling
period was significantly different between the three species it was
significantly longer on H. lignosum followed by H. ovalifolium and then
H. arabianense. The female ٣rd nymph instar period was significantly long
on H. lignosum followed by H. ovalifolium then H. arabianense. The ٥thfledgling nymph instar period was significantly long on H. lignosum
compared to H. arabianense. In this season total development period was
significantly long on H. lignosum. In case of the male and female it was
significantly longer on H. lignosum followed by H. ovalifolium and H.
arabianense.
Pfadt, (١٩٤٩), Rao (١٩٤٢) and (١٩٦٠), Uvarov (١٩٦٦), Bhatia and Ahlualia
(١٩٦٧) and Ibrahim, (١٩٧٢), mentioned the effect of food on the biology,
and cleared that the biology of the locust is influenced by the type of food
available to the insect in nature. In general it appears that H. arabianense
is suitable for development followed by H. ovalifolium, while H. lignosum
is not. In season ١٩٩٩-٢٠٠٠ there was no significant difference in the effect
of H. ovalifolium and H. arabianense on the maturation of fledgling male
and female, but when mixed data of male and female was taken negligible
difference was detected. It was significantly rapid on H. ovalifolium
compared to H. arabianense There is no significant difference in season
٢٠٠٠-٢٠٠١. Ellis, et al., (١٩٦٥) reported that the sexual maturity and
moulting of Schistocerca gregaria was influenced by monoterpenoids and
hormones from food plants. Also Steedman (١٩٩٠) mentioned that
immature adults might become sexually mature in few weeks or few
months, according to environmental conditions. From the previous studies
it was clear that H. ovalifolium and H. arabianense enhanced maturation,
so the two species influenced sexual maturation in the same manner. The
longevity of all nymph instar was significantly prolonged on H.
arabianense as compared to H. ovalifolium followed by H. lignosum in
season١٩٩٩-٢٠٠٠, In season ٢٠٠٠-٢٠٠١ it was significantly prolonged on
H. arabianense compared to H. ovalifolium which was significantly
prolonged compared to H. lignosum. Male and female longevity was
significantly short in H. ovalifolium compared to H. arabianense in season
١٩٩٩-٢٠٠٠. In season ٢٠٠٠-٢٠٠١ it was significantly prolonged on H.
arabianense followed by H. ovalifolium compared to H. lignosum.
In season ١٩٩٩-٢٠٠٠ all nymphs reared on H. lignosum died before
reaching the ٤th instar. While in season ٢٠٠٠-٢٠٠١ few individuals reached
the fledgling stage but died after fledgling and before maturation (in
maximum ٢days after fledgling). Nymphs reared on H. ovalifolium in
season ١٩٩٩-٢٠٠٠ and reached fledgling stage died before maturing except
few individual, However most individuals matured in season ٢٠٠٠-٢٠٠١.
Most individuals reared on H. arabianense reached the mature stage in the
two seasons.
It was mentioned in the literature that food plants affected individuals
survival and the water content of food affected the food consumption rate.
This has been confirmed by Williams (١٩٥٤), who found that fresh grass
was consumed more than dry grass when both were offered in the same
cage. According to Mulkern (١٩٦٦), Stolyarov and Waloff observed that
Schistocerca gregaria survived better on some plants than on others The
dry weight per gram was (٠,٣١٠, ٠,٢٦٥ and ٠,٢٩٤) in H. ovalifolium, H.
arabianense and H. lignosum respectively in season ١٩٩٩-٢٠٠٠. Where as
it was (٠,١٦٤, ٠,١٥٩ and ٠,٢٩١) respectively in season ٢٠٠٠-٢٠٠١. This may
explain the variation in development and survival obtained in the two
seasons during this study.
The three species of Heliotropium has no clear effect on the weight
of nymphs and fledglings. In season ١٩٩٩-٢٠٠٠ all nymph instars reared on
H. arabianense weighted more than those reared on H. ovalifolium, except
fledgling female, weight was significantly heavy in H. arabianense as
compared to H. ovalifolium. The male ٤th instar and fledgling female
weight were not significantly different. In season ٢٠٠٠-٢٠٠١ the ٣rd nymph
instar weighted significantly less when reared on H. lignosum compared to
H. ovalifolium and H. arabianense. The ٦th instar weight was significantly
higher on H. ovalifolium compared to the other two species. The ٤th, ٥th
and fledgling instar weight was not significantly different. In case of male
and female nymph instars the weight was affected in the same manner and
there was no significant difference except that the male ٦th instar weight
was significantly heavy in H. arabianense than other species and the
female ٤th instar weight was significantly heavy on H. lignosum compared
to H. ovalifolium. The weight gain of nymphs and fledglings in season
١٩٩٩-٢٠٠٠ was higher in those fed on H. arabianense than on H.
ovalifolium, followed by H. lignosum but the fledgling female gained more
weight on H. ovalifolium than on H. arabianense. It was significantly
heavy in (٣rd and ٥th nymphs instar), (male ٣rd and ٥th) and (female ٣rd, ٤th,
٥th) nymph instar. In season ٢٠٠٠-٢٠٠١ weight gain was not significantly
different, However in case of the ٤th nymph instar it was significantly high
in H. lignosum and H. arabianense as compared to H. ovalifolium. The
female ٣rd instar weight was significantly high in H. lignosum compared to
H. arabianense followed by H. ovalifolium.
The feeding rate of nymph instars increased gradually until the ٦th
nymph instar, then declined in the fledgling stage. In season ١٩٩٩-٢٠٠٠ the
٣rd and ٤th nymph instar consumed significantly few grams of wet H.
lignosum compared to the other species. Also the ٣rd and ٥th instar
consumed significantly few grams of wet food on H. ovalifolium as
compared to H. arabianense. The ٤th instar consumed significantly few
grams of wet food of H. arabianense. There was no significant difference
in the ٦th and fledgling stage. In season ٢٠٠٠-٢٠٠١ the nymphs consumed
significantly few grams on H. lignosum as compared to the other two
species. The ٥th instar nymphs consumed significantly more grams from H.
arabianense followed by H. ovalifolium then H. lignosum. In season ١٩٩٩٢٠٠٠ dry food consumed by solitary ٣rd and ٤th nymph instar was
significantly less in H. lignosum followed by H. arabianense as compared
to H. ovalifolium. In the other nymph instars and fledgling there was no
significant difference and it was slightly high on H. ovalifolium compared
to H. arabianense. In season ٢٠٠٠-٢٠٠١ only the ٤th instar, nymphs
consumed significantly few grams of dry H. lignosum compared to H.
ovalifolium and H. arabianense. Also the ٥th instar consumed significantly
more grams from H. arabianense compared to H. ovalifolium. Dry food
assimilated by solitary nymphs was significantly high in H. ovalifolium
compared to H. arabianense and H. lignosum in season ١٩٩٩-٢٠٠٠. In
season ٢٠٠٠-٢٠٠١ it was significantly high in the ٣rd instar in H. lignosum,
significantly high by ٥th instar in H. arabianense and significantly low by
٦th instar in H. lignosum compared to the other two species. There was no
significant difference in the other instars.
In conclusion and as mentioned above solitary nymphs fed well on H.
arabianense and H. ovalifolium while they fed little on H. lignosum.
However the assimilated food from H. lignosum was high compared to the
food consumed and nymphs excreted few grams of faeces.
The average fecundity and egg development was affected in the
same manner in the two species (H. ovalifolium and H. arabianense),
except in season ١٩٩٩-٢٠٠٠ the incubation period and number of pods per
female was higher on H. arabianense. Fertility of solitary females was
affected by the food species. In season ١٩٩٩-٢٠٠٠ females mated in
significantly few days on H. ovalifolium compared to H. arabianense. The
oviposition period took significantly short time on H. ovalifolium
compared to H. arabianense. H. arabianense significantly prolonged the
life span compared to H. ovalifolium. The influence mentioned above
probably reflect the effect of the seasonal climatic conditions that in turn
affected the quality of the two species.
Nymphs kept on the three species of Heliotropium together for ٢
days fed equally well on the three species, but when they were kept for ٦
days they consumed significantly few grams from H. lignosum compared
to H. ovalifolium and H. arabianense. Consumption rate was high on H.
arabianense than on H. ovalifolium. Also when they were kept in small
cages for two days negligible difference was found between H.
arabianense and H. ovalifolium, and nymphs consumed significantly few
grams on H. lignosum. This indicates that nymphs prefer H. arabianense
and H. ovalifolium than H. lignosum. The preference was not cleared when
the nymphs were left to feed for two days but it was clear when they were
kept to feed for ٦ days. According to Uvarov (١٩٧٧), Thomas mentioned
that the final selection is a matter of taste discrimination by the sensilla on
the mouthpart. Plants, which are only nibbled, but not eaten, are rejected
for their taste on chemical grounds.
When filter paper impregnated with the juice of the three species
was presented, nymphs consumed large areas of filter paper impregnated
with H. lignosum juice compared to H. arabianense and H. ovalifolium in
all paired and group tests. There was no significant difference between H.
ovalifolium and H. arabianense except in male nymphs and male + female
nymphs in paired test in small cages, where they consumed large area of
H. arabianense compared to H. ovalifolium.
This indicates that some volatile phagostimulating material or materials
were lost in the process of extracting the juice of H. arabianense and H.
ovalifolium. On the other hand, some volatile antifeedant material or materials
were lost in the process of extracting the juice of H. lignosum. Goodhue (١٩٦٣),
mentioned that refusal to feed on a plant after biting it, or its acceptance, led to
the theory that this depended on the presence or absence of some specific
substances termed phagostimulants.
Nymphs tested in wind tunnel to know their behavior during their
search for and finding the food spend significantly more time in walking
and resting. They jumped and climbed the walls significantly few times in
the presence of H. lignosum and most of the nymphs did not reach the
food. The average distance traversed was significantly short with this
plant. In case of the male there was no significant difference in the
behavior and the average distance traversed. Females spend significantly
long time in walking and resting and they significantly walked right, left
and back a lot of times when provided H. lignosum in the tunnel compared
to the other two species. The nymphs traversed significantly short distance
and didn’t reach the food. The attraction of Schistocerca gregaria hoppers
by the smell of food plants was mentioned by Volkonsky (١٩٤٢). Also
Haskell et al., (١٩٦٢) mentioned that in wind tunnel with air current
carrying the smell of crushed grass and of variety of odorous substances,
these odorous caused Schistocerca hoppers, starved for ٢٤ hours, walking
down wind to reverse their direction and walk twoards the source of the
odours. From the previous data nymphs prefer H. ovalifolium and H.
arabianense odours and walked down towards and reached the food.
Whereas they did not prefer H. lignosum odorous so they did not reach the
food in spite of few numbers walked the whole ١٤٠ Cm length of the wind
tunnel but they did not climb the food or bite it, instead they turned back.
CONCLUSION
The Influence of three species of Heliotropium on the development,
weight, feeding rate, maturation, fertility and fecundity, longevity, antifeedent
and repellency on the desert locust Schistocerca gregaria solitary phase was
carried out in this study.
H. ovalifolium and H. arabianense are suitable for male and female
nymph development, while H. lignosum was not suitable. Nymphs developed
fast on H. arabianense followed by H. ovalifolium. There was no clear effect
of the three species on the weight gain of nymph instars and fledglings, in spit
of the more weight gain on H. ovalifolium in season ١٩٩٩-٢٠٠٠. Nymphs and
fledglings’ male and female consumed more food when they fed on H.
arabianense or on H. ovalifolium, whereas they consumed less on H. lignosum
In spite of this the assimilation rate of the consumed food was high on H.
lignosum due to the fact that comparatively less food was taken and few faeces
pellets were voided
Fledgling male and female took a long time before maturing. The male
became mature before the female, on both the two species (H. ovalifolium and
H. arabianense). H. ovalifolium and H. arabianense affected the fertility and
egg development in the same manner, but all females preoviposition period
was long and laid few egg pods compared to literature reports. H. ovalifolium
and H. arabianense prolonged individual life. Most of the male and female
nymphs reared on these species completed development, but nymphs reared on
H. lignosum died before fledgling and the few that fledged died after a
maximum period of ٢ days.
Male and female ٥th instar nymphs kept on the three species of
Heliotropium together prefer H. arabianense, than H. ovalifolium especially
when they were kept for ٦ days. Nymphs provided with filter paper
impregnated with juice of the three species individually in-group and paired
test, consumed large areas from those impregnated with H. lignosum and a
small area from those impregnated with the other two species. The male
preferred filter paper impregnated with H. arabianense than those impregnated
with H. ovalifolium in paired test, while the female fed equally on them.
Generally nymphs didn’t prefer filter paper impregnated with these two
species. This indicates that some volatile phagostimulating material or
materials were lost in the process of extracting the juice of H. arabianense and
H. ovalifolium. On the other hand, some volatile antifeedant material or
materials were lost in the process of extracting the juice of H. lignosum.
Effect of plant smell on the behavior of male and female ٥th instar
nymphs as tested in a wind tunnel, cleared that nymphs prefer the smell of H.
ovalifolium and H. arabianense and they went towards the smell until they
reached the food. During that they moved their antenna some time, jumping
and walked left, right and back. The nymphs didn’t prefer H. lignosum smell as
they walked and rested for long periods, then turned back or climbed the wall.
Also they moved their antenna, but they didn’t reach the food and the few
individuals that reached the food, didn’t feed on it.
Finally this study revealed that H. ovalifolium and H. arabianense are
suitable food plants for the solitary phase in the locust breeding area compared
to H. lignosum. They are preferred by nymphs and fledglings. Also these
species provided suitable individual development. The two species must then
be the common key of locust survey in the Sahel Zone. H. lignosum was not
preferred, because of repellent volatile substance. It can be used as a source of
antifeedant to deter locusts from attacking field crops.
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