The pollen-carrying structure of a bee is called the scopa. In honey bees and bumblebees it is a concave corbicula on the hind tibia, into which pollen is moistened and pressed as a compact pellet. Megachilid bees instead carry a dense ventral scopa of stiff hairs on the underside of the abdomen and transport pollen dry and loose.
The dry load matters agriculturally. Loosely held grains are shed more readily onto stigmas, and this is part of why leafcutting bees are efficient pollinators of alfalfa, a crop whose flowers spring shut on visiting bees in a way honey bees learn to avoid. Males lack the scopa entirely, so a gold-dusted belly always means a female.
The leaf discs give the group its name. A female cuts near-circular pieces with her mandibles, flies them back rolled beneath her body, and lines a tube-shaped cell, then caps it with a smaller round disc before starting the next. The cuts are neat semicircles on leaf margins, most often on roses and similar plants, and the plant is not otherwise harmed; the bee takes tissue, not sap or seed.