Bee Nesting
All social and solitary bees build nests. Bees build their homes in a variety of places using an amazing array of materials. There are five different nesting styles among bees: ground nesters, wood and pith nesters, architects, cavity nesters, and renters.
Ground Nesters
Example of a nest aggregation.
Over 70% of bees build their nests by digging in the ground, making soil the most common material used by bees for nesting. Each species has a preferred soil texture. Some species prefer well-drained, sandy soils, others very silty soils, and others hard-packed, clay-like soils.
Ground nests can be as shallow as a few inches or extend as much as 10 feet deep! Female ground nesters dig with their mandibles and “bulldoze” soil with their abdomens. The population of alkali bees (Nomia melanderi) in Touchet Valley, Washington can move approximately 96 tons of soil in a year!
Ground-nesting bees sometimes build close to one another, forming a group of individual nests called a “nest aggregation.” These clusters can be gigantic, often with over 100,000 nests in one aggregation. The largest nesting aggregation ever found was built by the hairy-legged bee (Dasypoda plumipes) and contained over 12 million nests!
Nest aggregations can appear seemingly overnight and may stay in the same area for decades. One aggregation of grey-backed mining bees (Andrena vaga) lasted for over 60 years!
Nesting by Dawson’s burrowing bee (YouTube).
Nesting by Ptiloglossa bees (YouTube).
Wood and Pith Nesters
A small portion of bees build their nests in solid wood, pithy stems, and other similar materials. These bees use their mandibles to dig into wood and construct their homes.
Left (#2): Raspberry stems (Rubus). Many bees nest in pithy stems, such as raspberry and blackberry stems. Female Ceratina (the small carpenter bees) were found nesting in these Rubus stems in Ithaca, NY. Look for the hole at the end of the stem!
Right (#3): Japanese knotweed stems (Reynoutria japonica). This invasive plant can be used to make trap nests for stem-nesting bees. Japanese knotweed stems are hollow and variability in the stem diameter provides lots of possibilities for stem-nesting bees of varying sizes. Try making a “bee hotel” with knotweed stems in your neighborhood. You will be helping to control an invasive, non-native plant while helping bees find a nest.
Nesting by mason bees (YouTube).
You may be familiar with the large carpenter bees (Xylocopa) nesting in the trim of houses, barns, and sheds. Other wood nesters, like wood-borer bees (Lithurgus) and small carpenter bees (Ceratina), build their homes in rotten wood and pithy stems.
This split carpenter bee nest was collected in Arizona. Female Xylocopa californica arizonensis excavated tunnels in sotol (Dasylirion wheeleri) stalks. To partition the tunnels into discrete brood cells, they use wood fragments combined with salivary secretions. Note the discrete “fiberboard” brood cell partitions.
A bee nest in a clump of dried horse manure.
Some “wood nesters” are adapted to use other materials. Trichothurgus bolithophilus, a bee from the treeless plains of Patagonia, nests in dried horse manure. Before horses were introduced to Argentina in the 1500s, these bees probably nested in grass clumps.
Architects
Anthidiellum strigatum nest with the bee inside. Image copyright: Sebastián Jiménez López.
Some bees construct free-standing nests. These nests may be built with mud, resins, stones mixed with resin, plant fibers, and animal fur. Resin bees collect plant-based, sappy resin and use glandular secretions to build hard, water resistant nests. They sometimes decorate the nests with stones and pebbles. An African bee, Serapista, builds nests out of plant fiber, animal fur, and bird feathers glued to plant stems.
Cavity Nesters
Social bees, like honey bees and bumblebees, build their nests in cavities above or below ground. Honey bees build their nests in the open (some Asian species do this) or in cavities, such as tree hollows. The giant Asian honey bees (Apis dorsata and Apis laboriosa) construct massive nests on vertical cliffs or high in trees. Harvesting honey from these bees is a dangerous business. Bumblebees prefer below-ground nests, often in abandoned rodent burrows. In the early spring, you can see bumblebee queens searching for an abandoned burrow. They fly low over the ground and explore any hole or cavity that might make a suitable nest.
A bee nest hanging from high in a tree in Australia.
Renters
Example of a bee hotel.
Instead of making their own nests, some bees take over existing spaces. They nest in cracked stone, snail shells, beetle and worm burrows, hollow stems, and vacant nests of other insects. Renters also use manmade materials like straws (paper and plastic), fencing, tubing, and gaps in window frames. Renter bees include mason bees, leaf-cutter bees, and wool-carder bees.
Want to help “renter” bee species? Build a bee hotel!
One way that you can help preserve bees is to build a “bee hotel.” Bee hotels are a common sight in gardens and nature preserves in Europe. These structures generally consist of a roofed enclosure with a diversity of nesting materials for cavity- and wood-nesting bees. You can use tubes, bamboo, drilled wooden blocks, bricks, or any other materials that provide a range of holes and crevices for “renting” bees Once installed, the bee hotel will provide nesting sites for many different species of wasps and bees.