Technical Abstract: Over the past ten years we have studied the reproductive biology and pollination of 26 species of rare plants in the western United States from Nebraska to Nevada and Idaho to New Mexico. We have found that, contrary to conventional expectations, most of these rare plant species cannot automatically self-pollinate, nor can they set fruits parthenogenetically. Rather, viable pollen must be moved from dehiscing anthers to receptive stigmas by well-adapted pollinators to produce propagules sexually. In most cases those pollinators are native bees which nest in the ground or in wood structures such as dead snags and logs, and visit the flowers to collect pollen and nectar which they use to feed their progeny. These nesting sites may be in close proximity to the plants that the bees visit or they may be distant from those pollen and nectar sources. These bee pollinators of rare native plants are vulnerable to the insecticides usually sprayed to control grasshoppers on rangelands. Thus land managers should avoid spraying areas where pollinators are active at any time of the year. Buffer zones of at least three miles should be left around all rare plant populations to guard against needlessly destroying rare plant pollinators.