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The physical nature of pesticide deposits is an important factor in pesticidal activity. There is much literature on this aspect of insecticides. In general insecticides are more effective when in small particulate form but few investigations have been carried out on acaricides. Emulsions have been found to be more effective than suspensions when applied directly or indirectly as freshly deposited residues against mites (Ebeling and Pence, 1953). [...]

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The diversity and zoogeography of Diptera (Brachycera) of disjunct xeric grasslands in the southern Yukon were studied. Over 20,000 flies were collected representing 32 families and 213 species. In terms of abundance, the predacious guild dominated (54% of total specimens) due mostly to the family Chamaemyiidae which represented 45% of all specimens. In terms of diversity, the phytophagous and parasitoid guilds were dominant (25.5% of total species each). The most diverse families were Agromyzidae (32 species), Chloropidae (31 species), Tachinidae (23 species) and Pipunculidae (20 species). Thirty-four undescribed species were collected and 58 species were recorded for the first time in the Yukon. Zoogeographic analysis indicates that the Diptera fauna of these grasslands is dominated by widespread Nearctic or Holarctic species, but the fauna also includes southern grassland species with disjunct distributions, and species endemic to Beringia. The presence of endemic and disjunct species suggests that these grasslands were present in Beringia during the Wisconsinan and acted as a refugium for grassland Diptera.

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Growth is cyclic in nature, periods of activity alternating with periods of comparative rest (PEARL, 1925; WIGGLESWORTH, 1939). Many authors have attempted to construct mathematical expressions for this cyclic growth, in addition to ideal growth curves as an aid in the study of bionomics. Some of these will be dealt with later in this thesis where they prove relevant to the theme. The term “cyclic growth” may be broken down into its constituent parts: (a) it is well known that growth or increase in the bodily dimensions of an animal (or plant) can occur in two main ways, viz. (1) by increase in cell number (cell division); (2) by increase in the size of the cells already present. (Of course, production of cell products may also be considered growth.) The two modes of growth are not mutually exclusive. (b) The definition of “cycle” put forth by KLEITMAN (1949) will be used in this thesis, viz., “A cycle ..... is a repetitive series of events or successive changes of states, thus being either qualitative or quantitative in nature, and its own distinctive feature is one of order of occurrence, rather than duration. Cycles are intrinsic in origin; they may be influenced by inernal and/or external conditions, which affect them quantitatively, but seldom qualitatively.”[...]