This insect was introduced into the U.S. from Europe because of its high efficiency in pollinating certain crops, particularly alfalfa grown for seed. Both genders hover near flowers just like flies in the family Syrphidae. The male wool carder bee is significantly larger than its female counterpart, and aggressively patrols a territory, harassing  females (repeatedly attempting to mate by grabbing onto them and holding them immobile as shown in the accompanying photos) and driving off any other insects seeking nectar. Nesting females supposedly use the hairs (or "wool") from plants to line their burrows, using their mandibles to "card" the fibers into cell walls.

Leafcutting bees are important native pollinators of North America. They use cut leaves to construct nests in cavities (mostly in rotting wood). They create multiple cells in the nest, each with a single larva and pollen stored for the larvae to eat. Leafcutting bees are important pollinators of wildflowers, fruits, vegetables and other crops. Some leafcutting bees are even used in commercial pollination of cash crops such as blueberries, onions, carrots and alfalfa.

Leafcutting bees use the leaves of almost any broadleaf deciduous plant to construct their nests. Some species of leafcutting bees use petals and resin in addition to leaves. The most commonly reported problem of leaf cutting comes from ornamental plants such as roses, azaleas, ash, redbud, bougainvillea and other plants with thin smooth leaves. Some leafcutter bees will nest in thick-stemmed plants (such as roses and bamboo) with hollowed openings. You can prevent nesting in rose canes by sealing pruned ends with wax , thumbtacks, wooden dowels or white glue.

These bees are extremely aggressive, and harass any other insects vying for nectar. Both males and females are protective of their nectar sources. During the summer of 2005, these bees are abundant here near Chicago - many patches of flowers are overrun completely, and other pollinators driven off.

Leafcutting bees, as their name implies, use 1/4 to 1/2 inch circular pieces of leaves they cut from plants to construct nests consisting of several cells. Each cell contains a ball or loaf of stored pollen and a single egg. These nests are found in soil, in holes (usually made by other insects) in wood, and in plant stems. A diversity of cavities, such as shells of dead snails, holes in concrete walls and other holes in man-made objects are used as nesting sites. Most leafcutter bees overwinter in these nests as newly formed adults. In the following spring these adults chew their way out of the nest. Leafcutters are solitary bees and do not live in large groups or colonies like honey bees. Leafcutters do not aggressively defend nesting areas like honey or bumble bees.