Bumble bees are among the most recognizable and ecologically important insects in North America. Several species occur in Arizona, including the Western Bumble Bee (Bombus occidentalis) and the Yellow-Faced Bumble Bee (Bombus vosnesenskii). Unlike honey bees, bumble bee colonies are annual — queens overwinter alone and start new colonies each spring, with colonies rarely exceeding a few hundred workers. Bumble bees are critical pollinators for many native plants and agricultural crops, particularly those requiring buzz pollination (sonication) — a technique honey bees cannot perform. In Arizona, bumble bees are most active in cooler months and at higher elevations, as they are poorly adapted to extreme desert heat. They typically nest underground in abandoned rodent burrows, under logs, or in dense grass clumps. Bumble bees are generally non-aggressive and will only sting when their nest is directly threatened. Unlike honey bees, bumble bees can sting multiple times. Several bumble bee species in the western United States are in serious decline due to habitat loss, pesticide exposure, and disease.