No description available.

Thesis (MSc (Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 143-150).

Black flies (Diptera: Simuliidae) are one of the most medically and economically important groups of insects. In Africa and Central America they are the primary vector for Onchocerciasis (River Blindness). In the holarctic region they cause significant losses in meat production and are a serious medical and nuisance problem due to their biting activities. In Britain the nuisance problem asssociated with black fly biting activity is localized to Dorset and the Scottish Highlands where this study was carried out to identify the pest species, investigate their ecology and to determine possible control measures. Four species were observed biting humans; Simulium reptans, S. tuberosum, S. argyreatum, and S. variegatum of which S. reptans was the most important. The factors affecting their distribution and abundance in the egg, larval, and adult stages were investigated in the field. Possible control measures derived from these field studies are discussed. Feeding biology was studied using video and microscope observations and enviromental factors affecting ingestion rates, and feeding behaviour noted. Bioassays using Bacillus thuringiensis var. israelensis were carried out in the laboratory using a trough maintenance system. The effect of various factors on the efficacy of this bacterial insecticide are discussed in relation to its possible use in the field.

Study of the Entomophthorales infection in selected black fly populations from two outlets of a lake was conducted at the Reserve Faunique du Saint-Maurice (Quebec). Entomophaga near limoniae infected Simulium verecundum/rostratum, whereas Erynia curvispora predominantly parasitized Simulium decorum, and Erynia conica infected Simulium venustum and the Simulium verecundum/rostratum and Simulium vittatum complexes. This is the first report of the presence of Erynia conica and Entomophaga near limoniae in North America and Erynia curvispora in Canada. Entomophaga near limoniae in black flies represents a new association. / A successful method for rearing Simulium rostratum, and the in vitro production of fungal conidiospores, produced a sufficient supply of material to study the cuticular invasion process of Erynia conica in the laboratory. Both Erynia species exhibited a diurnal periodicity in the formation of secondary conidiospores in darkness in vitro. This mode of development was influenced by the pH of the medium. The cyclic pattern in secondary conidia formation by Erynia conica disappeared with exposure to light, which suggests that photoperiod may be a factor contributing to host infection. Only secondary type 2 conidia of Erynia conica produced germ tubes that invaded the cuticle of the proper host, Simulium rostratum as opposed to the primary conidia. The infective unit exhibited delayed germination and formed neither appressoria nor invaded the cuticle of the non-host, Simulium decorum, which may explain the host specificity observed in the field study. Cuticular lipids triggered appressoria formation and penetration pegs on the host black fly and did not seem to inhibit fungal invasion on the non-host. / The effects of selected physical factors on the development of the infective unit of Erynia conica were determined. Germination and sporulation in vitro were influenced by medium pH, environmental temperature and charge of the substrate, but both processes were independent of substrate hydrophobicity. Germination and sporulation occurred throughout the pH and temperature ranges tested, with both achieving maximum at pH 7.5-8.0 and 10-20$ sp circ$C. Temperature range of the germination of the conidiospores in situ was similar that in vitro, which corresponded to the temperature variation in the field. Production of invasive structures was noted for in situ experiments only and was more temperature sensitive than was germination.

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Sampling and analytical techniques to estimate abundance and productivity of stream invertebrates are examined for their precision and accuracy, and then utilized to develop empirical models of sampling variability, abundance, and growth rates of overwintering larvae of black flies (Diptera: Simuliidae). Sampling variability of density estimates of stream benthos increases with mean density, and decreases with sampler size. Artificial substrates do not consistently reduce sampling variability, and introduce variable bias in estimates of simuliid density. Growth rates of overwintering simuliids are mainly a function of their body size, but available data show that growth rates also increase with water temperature. Biomass of overwintering simuliids in lake outlets in Southern Quebec is positively related to chlorophyll concentration and current velocity, and negatively related to distance from the lake, water depth, and periphyton biomass. Computer simulations show that published methods fail to produce reliable confidence intervals for estimates of secondary production for highly aggregated populations, and a reliable method, based on the Bootstrap procedure and the Allen curve, is presented.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.