UK Bee Species

Sleepy Scissor Bee (Chelostoma florisomne)

Chelostoma florisomne (Linnaeus, 1758) · subfamily Megachilinae · family Megachilidae

The bee that sleeps in a flower

The sleepy scissor bee was described by Carl Linnaeus in 1758, in the founding work of zoological naming.^[3] Linnaeus called it Apis florisomnis, from the Latin flos, "flower", and somnus, "sleep", after the extraordinary habit of the males: in cool weather and at night they curl up inside the closed cups of buttercup flowers, sometimes clustered together, and pass the poor hours in a torpid sleep.^[3][5] In a warm meadow at dawn, a buttercup can be gently opened to find one, or several, small dark bees waiting for the sun. The genus name Chelostoma, from Greek roots meaning "cloven mouth", refers to the long projecting jaws the females use to work leaves and to shape mud in the nest.^[7]

Scissor bees, mason bees, and the shape of a Chelostoma

The sleepy scissor bee belongs to the Megachilidae, the family of mason, leafcutter and resin bees, whose members carry pollen dry on a brush of hairs beneath the belly rather than packed on the legs.^[7] Within the family the sleepy scissor bee is a Chelostomini, a small tribe with a very distinctive shape: long, thin and cylindrical, more like a black matchstick than a rounded honeybee.^[5] The "scissor" of the English name refers to a curious wedge-shaped projection on the underside of the male's abdomen, which he uses to grip the female during mating; the "large" in its other British name, large scissor bee, distinguishes it from the smaller Chelostoma campanularum, the bellflower scissor bee, which is only about six millimetres long.^[2] You can see where the Megachilidae sit alongside the other bee families in the World Bee Atlas.

A buttercup specialist

The sleepy scissor bee is oligolectic, meaning it collects pollen only from a single, closely related group of flowers, and in this case only from buttercups: bulbous buttercup, meadow buttercup and creeping buttercup are the main choices in Britain.^[1][5] Buttercup pollen is toxic to most bees, containing chemicals that irritate the gut, but Chelostoma florisomne has evolved the ability to detoxify or tolerate those compounds, a rare and specialised trick.^[4] Wherever there is a good stand of buttercups within reach, and a piece of sunny dead wood or a bee hotel for nesting, the sleepy scissor bee can turn up in surprising numbers.^[5]

Cavities, mud and one brood a year

The sleepy scissor bee is univoltine, with a single generation each year, and adults fly from May to July.^[1] Females nest in narrow tubes: old beetle burrows in sun-warmed dead wood, dry hollow stems of reed or bramble, drilled holes in wooden posts, and, more unusually, thatched roofs and the timbers of old buildings.^[1] The cell partitions and the nest plug are made of mud mixed with nectar, sometimes finished with small pebbles or sand grains embedded in the outer plug.^[8] Each nest holds a linear series of small brood cells, from just a couple up to a couple of dozen in the best sites.^[8]

Where and when you will see it

The sleepy scissor bee is widely recorded across England and eastern Wales, most often where meadows, woodland edges and gardens sit next to buttercup-rich pasture.^[1] Look for it between mid-May and early July on flowers of meadow, bulbous and creeping buttercup, and check the closed flowers early in the morning or late in the day for sleeping males.^[5] The main natural enemy is the sapygid wasp Monosapyga clavicornis, and, more occasionally, the odd ensign wasp Gasteruption jaculator, both of which parasitise the mud-plugged nests.^[1]

How to tell it apart

The one bee that seriously fools the eye is the smaller Chelostoma campanularum, which is only around six millimetres long and forages only on bellflowers (Campanula), so the flower alone is often the identification.^[2] The sleepy scissor bee is around ten millimetres, distinctly larger, with clean white hair fringes on the back edges of the first four abdominal segments in the female and a dense buff pollen brush beneath.^[2] Male sleepy scissor bees have a large, wedge-shaped projection on the second underside segment of the abdomen, and small bumps on the underside of the antennal segments.^[2] The related resin bee, Heriades truncorum, is a similar slim black bee but less specialised and less densely fringed.^[2]

Why the sleepy scissor bee matters

Buttercups are visited by many insects, but the sleepy scissor bee is one of very few for which they are the entire diet, and one of an even smaller group that has evolved a way around their toxic pollen.^[4] That makes it a small and elegant reminder that specialist pollinators depend on specific plants in specific places, and that a hedgerow field with a few buttercups will support insects that a mown lawn simply cannot.^[5] The species is also of interest to biologists as a model for solitary-bee nesting behaviour, and has been used in studies of pollen chemistry, cavity choice and cell construction.^[6]

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Dragos Nistor

Founder, HoneyBee & Co. · Guest Lecturer, University of Greenwich

HoneyBee & Co. draws on six generations of family beekeeping heritage, with honey from the Nistor family apiaries and from carefully chosen British producers. Our British honey supplier holds SALSA Certification, and we offer a 15% NHS Discount. Every jar is raw, unfiltered and traceable to the hive.