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Bryobia praetiosa Koch (1836) was formerly regarded as a complex of closely related species or races similar in morphological characters but varying widely in life-history, host plant specificity, and habits. The authors (30) have recently shown that two species, the clover mite, B. praetiosa Koch, and the brown mite, B. arborea Morgan and Anderson, can be distinguished in British Columbia on the basis of morphological characters. This paper presents ecological data in support of the morphological evidence. Review of Literature C o m o n NamesThe common names used for the B. praetiosa complex vary with the area and the principal host plants. It is usually called the clover or the brown mite in North America (9, 26, 28, 52) and the gooseberry mite in Europe (40, 57). Other common names are: almond mite, almond red spider, apple stem mite, brown almond mite, bryobia mite, clover spider mite, gooseberry red spider, ivy red spider, red apple mite, red mite, red spider, and spiny gooseberry mite (1,2,4,12,13,24,25,32,34,43,45,48,50). Distribution and HostsThese mites are of economic importance in many countries. They occur mainly between 20 and 60 degrees in both north and south latitudes (40). A report (1 1) from the tropics (Colombia) appears to be based on a misidentification as it mentions that the mites form dense webs, particularly in dry seasons. B. praetiosa is a non-webspinning tetranychid (2, 7, 26, 39, 46, 52). The mites have been recorded from low-growing herbaceous plants and from deciduous and coniferous trees. The recorded host plants are: (40) considered that B. praetiosa originally lived on mosses and other low-growing plants and became adapted to gooseberry. It was not mentioned in the literature as a pest on gooseberry until 1890 (1). In Europe its most important hosts are ivy, Hedem spp.; gooseberry, Ribes spp.; pome fruits; and low-growing herbaceous plants snch as legumes and various species of grasses. In most parts of Europe it is considered chiefly a pest of ivy and gooseberry, yet in other parts nf the world it is seldom recorded from these hosts. In Australasia it is reported chiefly on fruit trees and to a lesser extent on legumes and grasses. Host plant preference in North America varies considerably in different areas.In the central and eastern United States praetiosa is primarily a pest on clover and grasses; in the south and southwest it is common in orchard trees and is an import-lcontribution No. 3704,

Phytophagous orchard mites have become so troublesome in British Columhia during the last decade that special attention has been given to studies on their ecology and control. An iniportant rerequisite for such studies is an accurate and rapid method of estimating popn I ' ation densities of both the mites and their

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Phytoseiid mites are of cosmopolitan interest because they are predacious on many phytophagous mites (Tetranychidae, Eriophyidae, and Tarsonemidae) that are pests of agricultural crops. They have been studied in orchards (Collyer, 1953, 1956; Lord, 1949), vineyards (Mathys, 1955), citrus groves (Fleschner and Ricker, 1954; Muma, 1955), and strawberry plantings (Huffaker and Kennett, 1953, 1956), but few workers have recorded their presence in native environments. In the commercial fruit-growing areas of British Columbia, orchards are often planted near uncultivated areas of bush or grassland. The study on which these notes are based was undertaken to determine whether the phytoseiids that occur in these native sites become established in the orchards, and to obtain a knowledge of the entire phytoseiid fauna of the area, a necessary prerequisite to ecological studies of predacious mites in orchards.