A STUDY ON EGG DEVELOPMENT AND SURVIVAL IN LOCUSTA MIGRATORIA MIGRATORIOIDES (Reiche and Fairmaire) IN THE CHAD BASIN AREA

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dc.contributor.authorACKONOR, JOSEPH B.
dc.date.accessioned2014-07-11T07:11:22Z
dc.date.available2014-07-11T07:11:22Z
dc.date.issued1986-10
dc.descriptionA THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY TO THE AHMADU BELLO UNIVERSITY, ZARIA NIGERIA OCTOBER, 1986.en_US
dc.description.abstractField and laboratory studies on egg development, survival and hatchling weight in L. migratoria migratorioides were made at Ngala (12°20'N, 14°10'E) and Maiduguri (11°53'N; 13°16'E) in the Lake Chad Basin locust outbreak area. During 1981 to 1985 data on eggpods were compiled for four seasons namely, the rainy season (July to September); the harmattan (mid-November to February); the hot-dry season (March to mid-May) and the early rains season (mid-May to June), In the field locusts were bred in open-bottomed wooden frame cages in three soil habitats classified as sandy, sandy-clay loam and clayey. In the laboratory breeding occurred in cages provided with predetermined soil/water mixtures for oviposition; incubation temperature ranged from 22 ± 1°C to 40° ±1°C. The laboratory study centred on the age of the female in relation to fecundity and the effects of moisture — including flood and drought—and also of temperature, on egg development, survival and hatchling weight, A total of 907 eggpods were obtained in the field during the rainy season; these comprised 350 in sand, 298 in clay and 259 in sandy-clay loam. During the harmattan 49 eggpods were obtained, 24 in clay, 16 in sand and nine in sandy-clay loam soils. During the hot-dry season 35 eggpods were obtained; 16 of these occurred in clay, 11 in sand and eight in sandy-clay loam. Sixteen eggpods were obtained for the early rains seasons, eight in clay, seven in sand and one in sandy-clay loam. Egg development rate was inferred from incubation period; it was fastest in the early rainy season when the mean incubation period in sand was 9.5 days and corresponded to the highest mean air temperature ranging from 29.8 C to 36.2 C. Development rate was slowest during the harmattan; incubation averaged 24 days in clay and coincided with the lowest mean air temperature ranging from 19.2°C to 25.6°C. Average development rates for the rainy season were intermediate to those for the seasons mentioned above; the rates coincided with the intermediate air temperature ranging from 24.6°C to 27.3°C;incubation lasted 13.6 days in sand, 16,0 days in sandy-clay loam and 18.1 days in the clayey soil. Egg survival rate was inferred from the percentage of eggpods that hatched in a given eggpod population. The best survival rates were recorded during the rainy season when 49.9% of 350 eggpods survived in sand, 25.1$ of 298 eggpods survived in clay and 16.6% of 259 eggpods survived in sandy-clay loam. During the harmattan 11.4$ of 24 eggpods survived in the clayey habitat only and during the early rains 29.2$ of seven eggpods survived in the sandy habitat only; eggs did not survive in any habitat during the hot-dry season. Egg mortality factors under field conditions were identified as predation, parasitism, desiccation and decay. These factors were seasonally influenced. Predation was the major mortality factor, particularly during the rainy season; the major predatory suspects were larvae of coleoptera while a mite of the genus Allothrombium was a minor predatory agent. The parasites comprised Scelio africanus Remaudiere, S. sudanensis Remaudiere which belong to the family Scelionidae (Hymenoptera) and an unidentified worm of the family Enchytraeidae. The two parasitic groups caused minor mortality in the rainy season only. Desiccation and decay, which were prevalent during the drier and wetter seasons respectively, caused little mortality. Laboratory observations showed that the female locust laid a maximum of five eggpods, the mean being 2.9. The number of eggs per eggpod declined with the age of the female but development and survival rates, and also hatchling weight, were independent of parental age. Laboratory observations also indicated that development rate was influenced by soil moisture, including flood and desiccation; wetter soil conditions and drought retarded egg development. Development rate was also influenced by temperature, 34 ±1°C being the optimum at which the average incubation period was 10 days. Eggs survived at temperatures ranging from 22 ± 1°C to 38° ± 1°C; no egg survived at 40 ± 1 °C. Survival was higher in wetter soils but flood was detrimental. Older eggs survived better in flood but pharates about to hatch were highly susceptible. Drought was also detrimental to survival. Hatchlings emerging from wetter soils were heavier and had higher survival potentialsen_US
dc.identifier.urihttp://hdl.handle.net/123456789/5087
dc.language.isoenen_US
dc.subjectEGG DEVELOPMENT,en_US
dc.subjectLOCUSTA,en_US
dc.subjectMIGRATORIA MIGRATORIOIDES,en_US
dc.subject(Reiche and Fairmaire),en_US
dc.subjectCHAD BASIN AREAen_US
dc.titleA STUDY ON EGG DEVELOPMENT AND SURVIVAL IN LOCUSTA MIGRATORIA MIGRATORIOIDES (Reiche and Fairmaire) IN THE CHAD BASIN AREAen_US
dc.typeThesisen_US
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