Red storm rising

By Ron Rock, Bumblebee Conservation Trust Volunteer

Don’t worry, to the best of my knowledge we are not about to be invaded, at least not by a belligerent force. However, the forces of good are beginning to stir, nest hunting queen bumblebees are on the move, one of which was recently described to me as the size of a B52. If you own a patch of pulmonaria or early flowering comfrey keep an eye open for a small ginger bee with a distinctive high pitched buzz and whizzing flight for this will be a male hairy footed flower bee. This bee jealously guards his chosen flowers, only allowing females of the species to forage in his patch. This way the all black females gain a protected pollen and nectar resource and he gets to perform the function that male bees are designed for, all in all a rather neat arrangement!

Male red mason bee with white moustache             Female red mason bee, larger black face

Many more of our 240 plus species of solitary bees will soon be emerging including one of my very favourite creatures, Osmia bicornis, the red mason bee. Red mason bees are a univoltine (single brooded) spring flying solitary bee active from April to mid June and occasionally a little later. They are approachable and docile little bees which are not given to stinging and so are safe around children and pets. Like all bees it is only the females that carry a sting and it has been said that the only way a female red mason will sting you is if catch her and roll her between your fingers! Red mason bees are hugely beneficial to our gardens and crops as they are excellent pollinators of fruit trees, together with a wide range of wildflowers. A single female red mason bee can do the pollination work of 120 honeybees and may in the future be commercially reared to pollinate fruit orchards in the U.K.

Male red mason bees emerge around two weeks before the females. When the females emerge they are mated by the waiting males and immediately set to work establishing a nest. Red mason bees use mud to build a linear row of chambers that they provision with a mixture of pollen and nectar into which an egg is laid and the cell is then sealed and work begins on the next one. This method of feeding their offspring is known as mass provisioning, bumblebees and honeybees employ a technique called progressive feeding, where the larvae are fed by worker bees as they grow. It takes a female red mason bee between 1 -1.5 days to build and provision one cell. The eggs hatch after about a week and the resulting larvae eats the pollen and nectar in the cell.

Mating pair of red mason bees              A single egg is laid into the pollen and nectar mass                       

After around 56 days the larvae spins a cocoon and remains in this state within the cocoon for a further 48 days before metamorphosis into an adult bee takes place. The bees then remain quiescent within their cocoons until emergence time the following spring. The sole function of male is to mate with as many females as possible, drink copious amounts of nectar and eat pollen (well, boys will be boys). The males die off after about 6 weeks and the last females are active until mid June when they too perish. No red mason bee ever lives to see its own offspring and the sight of tattered and sun bleached almost grey females is a sure sign that spring is handing over to summer.

Developing larvae

Completed nest

In a completed nest, male (unfertilised) eggs are laid in the cells at the entrance (vestibular) end of the nest and these are the first to hatch out in the spring. The end cell is always left empty and sealed with a thicker wall of mud than used in cells containing the eggs. This is a form of protection from predators and other species of bees and wasps which might otherwise nest in the vestibular cell and make it impossible for the red masons to emerge from the nest, thus causing them to starve to death. The cocoons consist of two layers, an inner silky lining and a surprisingly tough outer layer. The cocoons are white when spun but soon revert to the familiar brown colour shown here. On hatching the bees secrete a substance that softens the outer layer of the cocoons to aid emergence.

Bee nesters (bee hotels)

These are some of my nesters at home, mason bees always look along edges for a nesting site, the linear edge in this case being provided by the hedge beyond.

Red mason bees are our most numerous osmia species and it is surprisingly easy to attract them into our gardens. All you need is a bee nester, I don’t like the term bee hotel as the name gives the impression of a short stay, when in truth the bees once established spend their whole life in and around these structures. They can be bought though I prefer to build my own as a lot of the commercially available ones are not too well made. The nesters are stocked with cardboard tubes and liners, bamboo or routed out wooden trays, 8mm is about right for red masons. Nesting cavities should be at least 160mm long. The boxes with the single holes are release chambers where cleaned and overwintered cocoons are placed each spring. I no longer use drilled out logs and I will expand on these last two statements later in the year.

'The Red Storm'

The males emerge first, a trickle then a flood. They spend their days jostling and jousting outside the nesters and occasionally nipping off to refuel before rejoining the riot whilst waiting for the emergence of the females. They seem to know when this will be as the activity becomes even more frenetic! Once mated the females start their nesting activity collecting mud in their mandibles and pollen on the underside of the abdomen. The males fade away and the activity becomes more ordered and fascinating to watch. These bees work so hard and by the end of June you are hopefully left with lots of tubes neatly capped off with mud. So sit back and enjoy these lovely little bees, they are like a fine wine served with the main course of bumblebees. A little later in the year, afters are served a la leafcutter bees, but that is another story!

Bliss! You can spend hours watching these cracking little bees!

Part 2 will follow in September/October when I will let you see how I look after the bees over the wintertime.

If anyone has any questions please feel free to e-mail me at

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