Call number: LD2668 .T4 1937 D41

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Thesis (M.Sc.)--York University, 2008. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 56-75). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR38744

Thesis (M.P.H.)--University of Michigan, 1946.

Thesis (M.Sc. (Environmental Biology)) -- Mahidol University, 1979.

Thesis (M.P.H.)--University of Michigan, 1946.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

The present product development project was aimed at studying the synergism and/or antagonism amongst various known insect repellent actives with the view to formulating a multi-active repellent product with improved properties when compared to current single-active commercial products. Advanced statistical methods were used to identify synergism between individual active substances and to define a formulation as close as possible to the “ideal” formulation. Several mosquito repellent samples were prepared and sent to the South African Bureau of Standards (SABS) in Pretoria to test for their efficiency in repelling mosquitoes. From the results of the repellency tests of the various active combinations, three actives were identified that showed promising signs of synergism. These actives were then studied in further detail to determine their optimum combination. In addition, it was shown that when using a natural flavourant as promoter and incorporating a slow-release agent into formulations for aerosols and lotions, a product is obtained that gives comparable levels of efficiency to current commercial products, but at much reduced levels of active loading. Accelerated stability tests performed on the final combination of the three actives used in the final formulation showed no adverse reactions over a three-week study. These tests shall be repeated once the final application form (lotion, aerosol, etc) and product packing have been decided.

A preliminary cytotaxonomic study of the common Chironomidae in a series of saline waters in the southern interior of British Columbia has been undertaken. The banding pattern of the salivary gland chromosomes, once it had been described, was used as a taxonomic criterion and as an indicator of the relationships between the groups involved. In order to obtain associated stages in the life cycle, the larvae were reared in individual vials. The polytene chromosome analysis revealed seven well defined larval species. The subsequent morphological analysis showed that five of these larval species could usually be separated by their external morphology. However, two cytologically distinct species are morphologically indistinguishable. Recent work on sibling species in Drosophila and Chironomus (Diptera) has shown that sibling species have salivary gland chromosomes with an identical banding pattern but, differ from one another in the frequency of inversions. The present study suggests that the morphologically identical larvae mentioned above are sibling species in larval morphology but are clearly separable by chromosome analysis. The fact that they occur together in the same lake tends to eliminate the view that they are distinct populations of a single species. That there may be more than one species involved in those here considered to be a single taxa, should however not be forgotten. / Science, Faculty of / Zoology, Department of / Graduate

The basic morphology and ultrastructure of the anal papillae of a saline water mosquito larva (Aedes campestris) have been investigated under two physiological conditions: (a) normal hyperosmotic external medium and (b) dilute hyposmotic medium. The ultrastructure of these organs suggests that they are not rudimentary, but rather are made up of cells that are morphologically specialized for transport. The anal papillae appear active in both the normal and dilute media and possible functions under the two physiological conditions are discussed. No major qualitative or quantitative differences were observed with the large change in external medium. This suggests that physiologically-demonstrated adaptive changes may require only minor structural alterations. The morphology and ultrastructure of the hind gut of A. campestris larvae were compared under two physiological conditions; normal (requiring hyporegulation) and dilute (requiring hyperegulation) external medium. No differences which might be associated with hyporegulation were observed. The rectum of A. campestri s was compared to that of Aedes aegypti. The rectum in the former is composed of two regions, an anterior and posterior rectum, while in Aedes aegypti, an exclusively freshwater mosquito larva, the rectum has only a single region. The rectal epithelia in both insects studied have morphological specializations for water and ion transport, and a consideration of quantative differences suggests that the posterior rectum is unique to Aedes campestris and hence could be responsible for the ability of this species to produce hyperosmotic urine. When the posterior rectal epithelium is compared to similar transporting epithelia in previously-studied terrestrial insects, several ultra-structural differences were noted. It is suggested that the mechanism of hyperosmotic urine production in saline water insects may be different from that in terrestrial insects. Several possible mechanisms of hyperosmotic urine production are discussed. / Science, Faculty of / Zoology, Department of / Graduate