Hollow stems and plant cavities

Bees that nest this way. Nesting habit decides what a garden has to provide — bare sunny soil, dead wood, hollow stems or nothing at all — and it is the half of bee conservation that flower lists leave out.

15 records · nesting habit

Mason beesOsmiaSolitary spring bees that build their nests out of mud, and the best orchard pollinators most gardeners have never noticed. A female mason bee works entirely alone: she finds a hollow tube, provisions a cell with pollen, lays an egg, walls it off with mud, and repeats until the tube is full. She will pollinate an apple tree several times more effectively than a honey bee while doing it, and she is almost incapable of stinging anyone.
Leafcutter beesMegachileThe bees responsible for the neat semicircular notches cut from rose and lilac leaves every summer. A female leafcutter bee cuts oval pieces of leaf with her mandibles, carries each one back curled beneath her body, and uses them to line and seal a nest cell — the cells end up looking like small green cigars. The damage to the plant is cosmetic and the bee is one of the most efficient pollinators in agriculture.
Wool carder beeAnthidium manicatumThe bee that shaves plants to line its nest, and the only common bee in which the male is substantially larger than the female. Male wool carder bees hold territories over patches of flowers and attack anything that enters — including honey bees and bumblebees, which they ram, grapple and occasionally kill using spines on the end of the abdomen. It is a small animal behaving like a much larger one, and it is now established on several continents where it does not belong.
Yellow-faced beesHylaeusThe bees that look least like bees. Yellow-faced bees are small, black, effectively hairless and marked with pale yellow or white on the face, and almost everyone who sees one assumes it is a small wasp. They carry pollen internally, swallowed into the crop and regurgitated at the nest, which means they have no pollen brushes at all — the feature people use to recognise a bee is simply absent. Seven Hawaiian species were the first bees anywhere to be protected under the United States Endangered Species Act.
Red mason beeOsmia bicornisThe bee in your bee hotel. Osmia bicornis is the commonest cavity-nesting solitary bee in northwest Europe, the one most gardeners actually manage to attract, and one of the most effective fruit pollinators known — a few hundred females will pollinate an orchard acre as thoroughly as a honey bee colony of tens of thousands. It is also, for practical purposes, incapable of stinging anyone.
Small carpenter beesCeratinaTiny, shiny, metallic dark-green or blue-black bees that excavate nests in the soft pith of broken stems — bramble, raspberry, elder, sumac — and then, unusually for a solitary bee, stay with their offspring. A Ceratina mother guards her nest through development and in some species is still alive when her young emerge, which puts the genus at one of the evolutionary staging posts between solitary living and true sociality.
Alfalfa leafcutter beeMegachile rotundataThe most intensively managed solitary bee in the world, and the animal that makes alfalfa seed production possible. Honey bees learn to rob alfalfa flowers from the side to avoid being struck on the head by the tripping mechanism, which means they gather nectar and pollinate nothing. The alfalfa leafcutter bee tolerates being tripped, and North American seed growers deploy it by the hundreds of millions.
Orchid beesEuglossiniBrilliant metallic green, gold and blue bees of the neotropical forest, and the only bees that collect perfume. Male orchid bees gather volatile aromatic compounds from orchids, fungi and rotting wood, store them in hollow chambers in their swollen hind legs, and use the resulting blend in courtship — a behaviour with no parallel anywhere else in the animal kingdom, and one that hundreds of orchid species have evolved to exploit.
Blue orchard beeOsmia lignariaNorth America's managed mason bee, and the species increasingly deployed alongside honey bees in Californian almond orchards because it does something honey bees cannot: fly in the cold wet weather that February almond bloom routinely brings. A few hundred females will pollinate an orchard acre as effectively as a full honey bee colony, and they are sold as cocoons in a box.
Blue mason beeOsmia caerulescensA small mason bee with a striking sexual difference — the females are metallic blue-black and the males bright golden-brown, so unalike that they are routinely recorded as two species. It nests in small cavities and seals cells with chewed leaf paste rather than mud, which sets it apart from its relatives.
Horned mason beeOsmia cornutaA large, strikingly marked mason bee of continental Europe — jet black in front and bright orange-red behind — and one of the species managed commercially for orchard pollination alongside the red mason bee. Females carry two conspicuous horns on the face, used to tamp mud into place.
Small scissor beesChelostomaTiny, slender, cylindrical mason-bee relatives that nest in the narrowest cavities of any bee — beetle holes barely two millimetres across — and several of which provision their cells with pollen from a single plant genus. The harebell carpenter bee uses campanula pollen and nothing else, and males sleep inside the closed bells.
Japanese orchard beeOsmia cornifronsA Japanese mason bee managed at scale for apple pollination since the 1940s, and introduced to the United States in the 1970s for the same purpose. In parts of Japan it pollinates the great majority of the apple crop, which makes it one of the few genuine success stories in deploying a non-honey-bee pollinator commercially — and, in North America, a naturalised species now competing with natives.
Patchwork leafcutter beeMegachile centuncularisThe leafcutter most gardeners actually meet, and the one responsible for the neat semicircular notches in rose and lilac leaves each summer. A female cuts an oval disc in a few seconds, flies off with it held beneath her body, and glues it into a thimble-shaped cell inside a hollow stem or a bee hotel tube.
Resin beesHeriadesTiny, cylindrical, near-black mason-bee relatives that gather sticky plant resin to seal their nests, and which specialise almost entirely on composites. They use very fine cavities, they have disproportionately large heads for their size, and a nest sealed with a shining resin plug is the sign they have been there.

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