THE ECOLOGY AND BIOLOGY OF OEDELEUS SENEGALENSIS KRAUSS (1877) (ORTHOPTERA : ACRIDIDAE} IN NIGERIA
THE ECOLOGY AND BIOLOGY OF OEDELEUS SENEGALENSIS KRAUSS (1877) (ORTHOPTERA : ACRIDIDAE} IN NIGERIA
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Date
1988-09
Authors
ANENE, CHINENYE
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Abstract
The distribution, ecology and biology of the
grasshopper, Pedaleus senegalensis Krauss, in Nigeria
were investigated. Results showed that the known
distribution of 0. senegalensis in Nigeria has
considerably increased, being extended and limited to
areas North of Latitude 9°N. These areas comprised
practically the Sahel, Sudan and northern one-third
of the Guinea savanna ecological zones. Observations
on the monthly fluctuations in the numbers of the
grasshopper in three ecozones showed that the grasshopper
was more abundant when rainfall was low, relative humidity
low, and temperature high. The difference in occurrence
and distribution of the grasshopper was a reflection of
the variations in the climatic and vegetation conditions
of the ecozones.
Seasonal population studies showed that the number
of the brown morph exceeded the green in all the ecozones
with an overall ratio of 3.4:1. The male grasshoppers
out-numbered the females with a ratio of 1.23:1 which was
significantly different from 1:1 at the 0.1% level.
Evidence from two peak populations observed over
the years of this study showed that 0. senegalensis has
two annual generations in Nigeria.
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Migration of adult populations of 0. senegalensis
suggested by the differences in numbers and stages of
sexual maturity of the day and night populations was
confirmed by morphometric analysis.
Adult female 0. senegalensis contained an average
of 40.51 + 2.4 ovarioles. The mean number of eggs per
pod of samples from the field and those laid in the
laboratory were 26.86 + 2.2 and 27,42 + 2.2 respectively.
The incubation period of the eggs ranged between
16.98 + 3.7 and 20.11 + 2.2 days.
The green and brown males, and green females were
morphometrically homogenous. Significant morphometric
differences existed between the green and brown dimorphic
females. Day populations were morphometrically different
from the night populations, indicating differences in
their spatial origin and the existence of the 0. grasshopper
in both solitaria and gregaria phases.
Three dipterous flies belonging to family Wemestrinidae
and Sarcophagidae were common parasites of the nymphs and
adults of 0. senegalensis. Numerous invertebrate and
vertebrate predators preyed on the nymphs and the adults
of the grasshopper. Birds were probably the most important
and regular predators of the grasshopper. One insect
parasite and eight species of insect predators were
important enemies of the eggs of 0. senegalensis
Description
A DISSERTATION SUBMITTED TO THE POSTGRADUATE SCHOOL
AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF
DOCTOR OF PHILOSOPHY IN ENTOMOLOGY
FACULTY OF SCIENCE
DEPARTMENT OF BIOLOGICAL SCIENCES
AHMADU BELLO UNIVERSITY
ZARIA
SEPTEMBER, 1988
Keywords
ECOLOGY,, BIOLOGY,, OEDELEUS SENEGALENSIS,, KRAUSS,, (ORTHOPTERA : ACRIDIDAE},, NIGERIA.