Bumble bees are highly significant pollinators in the Pacific Northwest. They are active from early spring to late fall, starting with the emergence of queens who search for food to establish their colonies. One remarkable characteristic of bumble bees is their ability to buzz pollinate, where they vibrate flowers at a specific frequency, causing trapped pollen to be released. This ability makes them effective pollinators for plants like tomatoes. Bumble bees are generalists, visiting a variety of plant species rather than focusing on just a few. They have extensive ranges and play the role of keystone species, upon which many other species depend in ecosystems.
Physical Description: Bumble bees are easily identifiable by their large, fuzzy bodies with distinctive black and yellow banding. Some species may also have white or orange markings. Similar to honey bees, they carry moistened pollen on their hind legs.
Common species in the Pacific Northwest: Black tail bumble bee (Bombus melanopygus), fuzzy-horned bumble bee (Bombus mixtus), yellow-faced bumble bee (Bombus vosnesenskii), California bumble bee (Bombus californica).
Known for their use of mud as a building material, mason bees create cell divisions in their nests. Supporting populations of wild mason bees can involve providing access to mud. Unlike bumble bees, mason bees are solitary insects that make their nests in natural above-ground cavities. In the spring, the female mason bees mate and gather nectar and pollen provisions for their nests. Each female finds a hole or tunnel to create separate compartments for her eggs and seals the entrance. The larvae hatch, feed, hibernate in cocoons through winter, and emerge in spring to continue the life cycle. Mason bees are efficient pollinators and remain active from spring to late summer. While commercial mason bees are sold for pollination purposes, caution should be exercised, as they may negatively impact wild, locally native mason bee populations (see 'Downside to the Mason Bee Trade').
Physical Description: Mason bees often have exoskeletons displaying metallic coloration ranging from green to teal. They have a narrower body compared to leafcutter bees and also collect pollen underneath their abdomen.
Common species in the Pacific Northwest: Blue orchard mason (Osmia lignaria), Osmia brevis, Osmia occidentalis, Osmia pusilla.
Understanding and identifying these major bee groups while gardening or exploring nature in the Pacific Northwest can contribute to a greater appreciation and conservation of these vital pollinators.
Leafcutter bees, scientifically known as Megachile, possess distinct characteristics and exhibit specific behaviors. These bees are appropriately named due to their unique ability to cut sections of leaves or petals, which they use to create cell divisions within their nests. Leafcutter bees have well-developed mandibles, or oral appendages, that are specially adapted for cutting plant material. Their heads are wider than other bee species, aiding them in snipping pieces of vegetation with precision.
Unlike some other bees, leafcutter bees nest above ground in preexisting holes within wood. These nesting sites are often in tight spaces, which has resulted in an interesting adaptation among them. Instead of carrying pollen on their legs like most bees, leafcutter bees carry it underneath their abdomen. This strategy allows them to navigate their narrow nests without any hindrance. Their distinctive feature, and another common name they are known by, is "hairy-belly bees." This name refers to the specialized hairs, called "scopa," present on their underside, which are used for collecting and transporting pollen.
When foraging on flowers, leafcutter bees employ a unique posture that sets them apart from other species. They often raise their abdomen, preventing it from inadvertently wiping away the precious pollen deposited by the flowers. This behavior not only distinguishes them visually but also ensures effective pollination. Although leafcutter bees may cause superficial damage to some garden plants through their leaf-cutting habits, their contribution as productive summer pollinators outweighs any potential harm they may cause.
Mining bees, as their name suggests, are a type of bee that excavates their nests underground. They are commonly found nesting near blueberry plants and are one of the primary pollinators for this fruit, along with bumblebees. It is worth noting that Andrena astragali, a native species of mining bee, specializes in pollinating the death camas plant of the Zigadenus species, earning it the rather unfortunate name of "death camas bee."
Unlike social bees, mining bees are solitary creatures. Each female bee creates a few nests during her relatively short lifetime, which typically spans between four to eight weeks. These nests are usually constructed with approximately five cells or chambers, which are provisioned with ample pollen for the developing bee larva. The female deposits a single egg in each cell and seals it with mud, hence never personally encountering her offspring.
After hatching from the egg, the mining bee larva relies solely on the stored pollen for nutrition. It consumes all the provisions, undergoing metamorphosis until it finally emerges as an adult bee. Following this developmental phase, the adult mining bee spends the remainder of the year and winter in a state of diapause, which is essentially a period of suspended development underground. It awaits the appropriate seasonal cues, such as temperature and moisture changes, that indicate it's time to rise to the surface. Once emerged, the mining bee resumes its role as a pollinator, contributing to the reproductive cycle of plants and the overall ecosystem.
Sweat bees, as their name suggests, have a unique characteristic of collecting salt from animal sweat, including humans. Unlike the typical black and yellow coloring associated with bees, sweat bees are small and dark, often leading to confusion with flies. Despite their small size, they play a crucial role in pollination by delving deep into flowers and dedicating ample time to drinking nectar and collecting pollen. Sweat bees exhibit a quasi-social behavior, with mothers and daughters cohabiting without any labor division or reproductive suppression similar to that seen in colonies with a queen. Due to their adaptability, sweat bees are commonly found in both urban and agricultural environments. In terms of appearance, they are typically black or dark metallic grey, with some species featuring pale hairy strips on their abdomen. These bees carry dry pollen on their hind legs. Noteworthy sweat bee species in the Pacific Northwest include the small sweat bee (Halictus tripartitus), the medium sweat bee (Halictus ligatus), and the tiny sweat bee (Lasioglossum species).
