Previous studies concluded that species in the coccinellid genus Stethorus Weise, although obligate predators of tetranychid mites, exhibit a strong numerical response only to high population densities of their prey. The study reported here was conducted to test the hypothesis that in western Washington red raspberries, Stethorus punctum picipes Casey is capable of detecting and attacking spider mite populations of very low density which are distributed in small, widely scattered patches during the early part of the growing season. In addition to using conventional leaf sampling methods, S. p. picipes interactions with prey were examined by observing their response to prey patches introduced into the field from laboratory cultures. Our results indicate that S. p. picipes is active at low prey densities, although undetected by conventional sampling methods, and is capable of locating rare, small prey patches. This finding suggests that dispersal and searching ability, rather than numerical response are the key components of this preypredator association. KEY WORDS Stethorus punctum picipes, spider mites, raspberry PREVIOUS STUDIES OF Stethorus Weise spp, con
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