The chaetotactic nomenclature proposed by Lindquist and Evans (1965) for the Gamasina, using the family Ascidae as examplar, is adopted for use in the family Phytoseiidae. Probable setal homologies were determined by: examining and comparing ontogenetic relationships in both the Phytoseiidae and Ascidae; standardizing the shape and size of the dorsal shield of exemplars from 7 genera of Phytoseiidae and one of Ascidae in order to compare standardized, transformed setal positions; examining the spatial relationships between setal and pore positions. The technique used to standardize the shape and size of the dorsal shield is described. The setal nomenclature adopted for each of the genera of Phytoseiidae is discussed and presented in diagrammatic form. Ventral chaetotaxy in the Ascidae and Phytoseiidae is also discussed.

The influences of wind and snow distribution at the tree line near Churchill, Manitoba, were studied. Wind profiles above the snow surface, snow crystal size and quantity were examined during abrasion experiments with white spruce branchlets. For white spruce, the abrasion zone was evidently within 80 cm above the snow surface, and needle removal by abrasion was strongly influenced by branch age. Removal by abrasion of similar-aged needles was highest in new branches and declined with branch age up to 7 or 8 years, and then In forest-tundra environments the matted forms of trees were snow covered early in winter and received little abrasion. Sparsely needled islands of trees were largely covered with snow at the base. More densely needled trees and some trees within woodlands were less exposed to abrasion. The blockage of air flow resulted in high-speed jets, which cleared out snow within a "horseshoe-shaped vortex" around the base of the tree. Both in much of the woodlands and in the open forest, snow abrasion was minimal or non-existent and snow load on the branches (qali) becomes the prevalent stress. During winter, a large proportion of the snowfall was initially blown off the exposed surfaces of Hudson Bay and the coastal tundra regions, into the woodlands, and eventually across the tree line and into the open forest. As the woodlands filled up with snow in midwinter , the rate of snow accumulation in the forest increased from double to triple the snowfall. Variations in the rate of accumulation occurred with wind speed and direction. During May, snowmelt began on exposed tundra first and usually ran off the frozen surface. Snowmelt occurred about three weeks later in the open forest and was characterized there by less runoff, as the water more readily permeated the thawing peat. The late snow beds are characteristic of the forest-tundra woodlands and were usually gone by mid-July. The woodlands were snow free for 1.5-2 months during the year, while the open forest was snow free for about 3 months and the tundra was largely snow free for 6 months or more.

Three genera in the subfamily Phytoseiinae (Acarina: Phytoseiidae) are known to occur in Canada and Alaska: Phytoseius Ribaga, Amblyseius Berlese, and Typhlodromus Scheuten. Chant (1965b) reviewed the genus Phytoseius in Canada. The present paper, based on examination of more than 5000 specimens, describes, keys, and figures the 48 species of Amblyseius known to occur in Canada and Alaska, and includes full collection records. Thirty-two new species are described. Chant's (1965a) generic diagnosis is followed.

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