plasterer bee

plasterer bee, (family Colletidae), large family of bees with more than 2,500 species found worldwide. Their common name, which is often used to refer to the bees of the genus Colletes, is derived from the protective, cellophane-like material that females secrete and plaster to the walls of their brood cells—a behavior unique to the family. Plasterer bees are cosmopolitan in distribution, with centers of diversity in Australia and the Americas. Like most bees, plasterer bees are solitary and do not produce honey. Plasterer bees are extremely docile by nature, and, although the females are capable of stinging, they rarely do so unless stepped upon or physically threatened. The insects are considered native pollinators, which means they coevolved with the flowering plants in the areas in which they live and are invaluable to the pollination of wild plants.

Physical description

In general plasterer bees are similar in size and shape to western honeybees (Apis mellifera). They typically have a brownish hairy head and thorax, compound outward-angled eyes, a heart-shaped face, and a pointed pale-banded abdomen. They characteristically have a linelike groove (called a suture) at the base of each antenna and a short tongue that is either bilobed at the tip or truncated. The females of most plasterer bee species have dense tufts of hair on their femurs, known as scopa, that serve as pollen brushes. Electrostatic forces on these hairs attract pollen to the bees’ bodies.

Life cycle

Plasterer bees are found in a variety of habitats, including forests, grasslands, wetlands, and backyards. They typically nest in the ground in tubes that the females excavate in bare sandy soil; these can reach depths of 15 cm (6 inches) or more. They also sometimes nest in hollow stems or cavities in wood and may utilize human-made “bee hotels,” which provide holes and canes of different sizes. Although the bees are solitary, some females nest in close proximity to each other, forming what is called a nesting aggregation.

Prior to excavating their nests, the females mate with the males while rolling on the ground or while flying. Males die shortly after mating. The female then builds the nest with multiple nest, or brood, cells, each of which is lined with a polyester that she secretes from her salivary glands. This helps protects the eggs from moisture that could promote the growth of fungi or other pathogens. She provisions each nest cell with a mix of water, nectar, and pollen before depositing a single egg. The cell is then sealed, and she repeats the process in other brood cells. The eggs hatch a few days after they are laid, and the larvae feed on the food provisioned by the mother bee. To pupate, each larva builds a cocoon within its nest cell and overwinters. The adult bees emerge the following year. Plasterer bees typically produce one generation of bees each year.

Adult plasterer bees are largely generalists and are known to visit a wide variety of plant species with shallow or open flowers, which can accommodate their short tongues. Some species have a preference for flowers in the Asteraceae (e.g., daisy, sunflower, and aster), Apiaceae (e.g., carrot, fennel, and parsley), and Fabaceae (e.g., pea, legume, and wisteria) families.

Major genera and conservation

The family Colletidae comprises 90 genera across five subfamilies. The largest genus is Hylaeus, with over 500 species found on all continents except Antarctica. Also known as yellow-faced bees or masked bees, Hyalaeus species are somewhat wasplike in appearance and characteristically carry pollen in their crop rather than externally. Another large genus, Colletes, with about 500 species, occurs primarily in North America. Several of these are listed as endangered on the IUCN Red List of Threatened Species, including Colletes merceti, C. wolfi, and C. sierrensis.

About 40 species form the genus Caupolicana, which is exclusive to the Americas; the bees are crepuscular, meaning they generally only visit flowers at dusk or dawn. With a similar number of species and distribution, Ptiloglossa is composed of nocturnal bee species that forage primarily in the predawn hours or after dusk.

Plasterer bees are most diverse in Australia, and about 50 percent of all Australian bees belong to the family. Genera dominantly or exclusively found in Australia include Euhesma, Euryglossa, Euryglossina, Leioproctus, Palaeorhiza, Sericogaster, and Xanthesma. Hesperocolletes douglasi, the only member of its genus, was thought to be extinct until its rediscovery in 2015 in Western Australia.