Studies on the reproductive status, catch and age compositions of the tsetse fly, Glossina pallidipes populations in the Nechisar National Park in southern Ethiopia

Abstract

Studies were conducted during the dry hot period of December 1999 to April 2000 in the Nechisar National Park, Southern Ethiopia, to obtain base line data on catch, age compositions, and reproductive status of samples of Glossina pallidipes, trapped in NGU-2G traps. The objective was to assess tsetse population dynamics and to provide data on the temporal and spatial variations of the structure of the fly population at five localities (habitats). The data were to be used for the suppression phase of a Sterile Insect Technique (SIT) project in the study area. Population study in space was conducted at randomly selected five sites in and out of the park. In each vegetation type, a set of 2 NGU-2G traps baited with urine and acetone were deployed for five days during the same week of the study time. Female flies were dissected to assess ovarian age structure of populations. To determine the age of male flies wing-fray analysis was carried out using wing-fray categories (1-6). Trapped tsetse included significantly higher proportions of teneral and non-teneral females, and a lower male: female ratio. Insemination rates of the sampled flies were over 95% at all habitats. In any one habitat, the frequency of pregnancy (egg stage) predominated, followed by the first, second, and lastly, by the third instar larva. Abortion was the predominant reproductive abnormality at all habitats of the natural population of G. pallidipes. Age compositions of females (ovarian aging) showed greater proportions of females with 1–3 ovarian age categories and a physiological age between 8–40 days at all habitats. Age compositions of males (wing-fray) were significantly greater for young males (1–3 wfc) compared with old males (4–6 wfc). The studies of this base line data collection with other operational studies will be a prerequisite to assess the feasibility of the proposed area wide eradication project and to develop appropriate strategies to suppress and finally to eradicate the fly by situational releases of sterilized male flies.

Key words/phrases: Abortion, age reproductive status, Glossina pallidipes, NGU-2G traps, pregnancy


SINET: Ethiopian Journal of Science Vol. 28 (1) 2005: 51-60