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Accueil du site → Doctorat → Canada → The natural history of Imbrasia belina (Westwood) (Lepidoptera : Saturniidae), and some factors affecting its abundance in north-eastern Botswana

University of Manitoba (1996)

The natural history of Imbrasia belina (Westwood) (Lepidoptera : Saturniidae), and some factors affecting its abundance in north-eastern Botswana

Ditlhogo, Marks K.

Titre : The natural history of Imbrasia belina (Westwood) (Lepidoptera : Saturniidae), and some factors affecting its abundance in north-eastern Botswana

Auteur : Ditlhogo, Marks K.

Université de soutenance : University of Manitoba,

Grade : Doctor of Philosophy (PhD) 1996

Résumé
Imbrasia belina moths produce larvae which have long been harvested by locals for domestic consumption. The exploitation of these larvae recently became commercialised. Prior to this study, there was little information about the natural history and factors affecting the abundance of this species. This lack of knowledge means that these populations can not be properly managed, and are therefore in danger of being overexploited. The biology of I. belina was studied by collecting data on its natural history, and by determining mortality factors affecting its eggs, larvae and pupae. Aspects of insect/plant interactions such as species and age of plant, and size of canopy were also studied. I. belina produces two generations per rainy season in north-eastern Botswana, and emergence of the moths appears to be dependent on rainfall. Egg mortality is due to parasitism, infertility and pharate larvae. Larval growth rate is constrained by the leaf-water content of this host. Arthropods and birds can cause significantlarval predation. Larvae can also be parasitised, the impact of which is greatest on the pupal stage. There was evidence that egg laying decisions are density-dependent, and also that moths preferentially lay their eggs on Colophospermum mopane. Defoliation was found to affect the reproductive success of the host. Information learned about this species was then incorporated into a simulation model to identify factors which could be important in its population dynamics. The model was then used to explore a range of harvesting possibilities for the sustainability of these populations. It appears that for the management of I. belina, the importance of rainfall in the population dynamics of this species may overshadow most of the biological processes of the system, such that management decisions can be made based on rainfall.

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Page publiée le 5 février 2018