Technical Abstract: We tested the hypothesis that Lima bean Phaseolus lunatus L. (Henderson cultivar) trichome density affects the survival of the acariphagous lady beetle Stethorus punctillum Weise. When isolated throughout larval development, 10% or less of S. punctillum larvae reared on two-spotted spider mite Tetranychus urticae Koch on small P. lunatus leaves survived until pupation. Trichome density (i. e., number of hooked trichomes per cm) was greatest on the underside of small leaves and least on large leaves, indicating that survival rate increased as trichome density decreased. Hooked trichomes impaled S. punctillum larvae more often at the apex of the abdomen than at any other body part. Hooked trichomes also trapped S. punctillum adults, but they always managed to free themselves. Hooked trichomes did not trap or impale spider mite nymphs or adults. This study highlights the discriminate effect of Lima bean trichomes on a predacious lady beetle and an herbivorous mite.