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. vii 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
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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.
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