Bees are flying insects of the ancient¹   order Hymenoptera². Estimates vary, but there are believed to be somewhere in the region of 20,000 different species of bees. Usually, when we think of bees, we tend to visualise the 'busy' bumble-bees or the 'selfless' honeybees - i.e. social bees that swarm, sting, collect honey and live co-operatively in colonies. But actually, most bee species are solitary. Many are stingless, some are parasitic and a very few are even carnivorous³.

There is enormous variety across the different bee species - with a remarkable range of sizes⁴, colours⁵, shapes, degree of hairiness, life styles and longevity⁶. For all this variety, they do have some things in common. Bees have two pairs of wings (like many other insects) - front and hind held together by rows of minute hooks. The flight muscles can be decoupled from the wings so that they can be vibrated in order to warm up the bee or the brood (and it's the vibrating flight muscles that make that very pleasing buzzing sound we associate with bees). They have elbowed antennae⁷ (as do the other Hymenoptera), compound eyes, ocelli⁸, extendable sucking tongue, mandibles for biting and chewing, a crop⁹ and branched or feathery hairs.

Bee larvae, in most cases, are fed mainly on pollen and nectar gathered and stored by adult female bees. The methods of storing pollen, nectar and floral oils, depends on the species of bee.

Most solitary bees burrow into soil or wood and construct a series of cells. Mason bees don't burrow, but do construct cells using mud and saliva. These bees all provision their cells with a blob of pollen, moistened with nectar (a few also use floral oils), and then they lay an egg before sealing each cell.

Between the solitary bees and the social bees is a whole spectrum of life-styles. Some bees nest together but raise only their own young - like a commune. Others take a step closer to the colonial (hive) model, with maybe half a dozen or so females who can all lay eggs, but one of them is the main egg layer - almost like a queen bee - and the others carry out most of the foraging and feeding. Then there are bees that live in very small colonies comprising a mother and a few daughters - and the mother ('queen') is indistinguishable from her daughters. These communal arrangement break up at the end of a season, when most of the bees die and next season's queens fly off to start a new family (or hibernate in colder climates). The honeybees, on the other hand, form large, permanent colonies, made up of specialist castes: queen, workers and drones, with each caste physically as well as behaviourally different.

It's possible to trace the evolution of social bees from the solitary and semi-social bees through all the intermediate steps that can be observed in bees living today.

So much variety takes a long time to generate: many millions of years. But now some of that rich diversity is being lost, as a result of habitat loss, introduction of pesticides, transporting of species and diseases into new areas, and so on. Many species are likely to be lost without ever having been recorded.

There are so many bee species, and so little is known about most of them, that the seven species described here in varying degrees of detail, can only convey a very inadequate impression of the astonishing breadth of all that diversity.

Bumblebees

Bumblebees are the big fuzzy 'teddy bears' of the bee world. There are about 250 known bumblebee species, of which 25 or so live in Britain - or did before several became extinct.

Like most bees, they feed on flower products and like honey bees, they are social. Unlike honeybees however, they cannot pass nectar to each other directly, mouth to mouth. They do make a little honey, but mostly use up their nectar supplies quickly without converting it. They don't build up great stores of food, and they don't live in perennial colonies many thousand strong. Colonies may build up in numbers to a few dozen, or even a few hundred bees by the end of a season, depending on the bumblebee species.

These fat, furry bees can live in colder climates than other bees, but in cooler latitudes, as winter approaches all but the new queens die. Then their majesties have to find somewhere to hibernate until spring.

Since a bumblebee queen generally lives no longer than a year, and has to find a gentleman bee, mate, find somewhere to doss for the winter, gather stores, find a suitable nest site, dig the nest chamber, make wax storage cells and brood cells from her own wax, lay eggs, feed the first batch of larvae - all before she has a single helper - the colony doesn't have time to reach honeybee proportions by the end of the seasonal cycle when all the workers and drones die.

Cuckoo bees

Honeybees

There are fewer than 10 species of honeybee world-wide and these are further divided into more than 40 subspecies. The ones that we are most familiar with, are the domesticated European honeybees: Apis melifera. They originated in Africa and spread north, speciating to suit the environments where they settled. In recent times, the various subspecies have been cross bred to produce more robust hybrids for disease resistance and higher honey yield¹⁰.

These are the highly social bees that live in large, perennial colonies - unlike those semi-social bees whose communal arrangements only last for a season. Honeybees collect nectar which they store as honey in wax combs (honeycomb) and the colonies' queens lay eggs in a central area of the comb (brood comb), where they hatch and are fed and cared for by female worker bees, until they pupate and mature.

They lifecycle is very rigid:

Timing varies from hive to hive, but the queen usually starts laying when the weather is still cold, stimulated by the lengthening days - around February in Britain. She 'decides' whether she will lay a male (unfertilised¹¹) or female (fertilised¹²) egg, depending on the dimensions of the cell she lays it in. It's the workers that 'decide' on the size of the cells. When it's time for the queen to make drones, they build a section of larger cells. This is known as drone comb. When they decide they want new queens, they make bigger cells beyond the normal limits of the brood comb. These generally hang vertically, on the face or bottom of the brood comb and the queen lays a fertilised egg in this type of cell. Queens are made, not born. The egg that a queen hatches from doesn't differ in any way from worker eggs. Whether the bee becomes a worker or a queen depends entirely on how the larva is fed. All honeybee larvae are fed royal jelly (which is a sort of insect-produced milk, secreted by the pharyngeal glands of the worker bees), for the first three days after hatching. After that, the diet of workers and drones changes to pollen and honey. Those larvae destined to become royalty continue on the diet of royal jelly until they spin their cocoon¹³ and the workers cap the cell with wax.

The young queens emerge about a week after sealing, then take another five days to mature. Workers take almost twice as long to pupate, at about 13 days and drones take about 16 days before they emerge. Both workers and drones then take a further two weeks to mature. That royal jelly really accelerates the rate of queen development. Even before they mature - very soon after climbing out of their cell - worker bees start to work.

Like ant colonies, honeybee colonies are often referred to as "superorganisms". The individual insects cannot survive for long if separated from the family. They can only function properly as part of a whole colony, so increase is made by the propagation of colonies rather than individuals. Honeybee propagation occurs when a colony divides. This often happens within a day of the first queen cell being capped. The old queen (having slimmed down ready for flight) will take to the air with about half of the flying population of the hive, in search of a new home. If all goes well back at the old hive¹⁴, the first queen to emerge will find and kill any rival queens (hatched or unhatched). After about a week, she will take some practise/orientation flights, find the local drone congregation area and then she will take her mating flight, during which she will mate with several drones from neighbouring colonies - the more the better. If she doesn't get sufficient sperm during her first mating flight she may make further mating flights in the following days, until her spermatheca is filled. And about a week after mating she'll begin to lay. When nectar and pollen are at their most plentiful, she can lay up to 2,000 eggs per day. A queen can live as long as five years, but two or three is more usual.

Drones, once they've matured, have a more or less 'nine-to-five job'. They fly from the hive in the morning, hang out with the gang of local drones in the drone congregation area, waiting for queens to mate with, and fly home at the end of their working day - unless they managed to catch and mate with a queen, in which case they die after mating and don't return home to their mother and sisters. If they fail to mate, and are still hanging around the hive by autumn, their sisters will evict them from the hive to starve and die. They have no defence against this harsh treatment. Drones depend on their sisters to feed them, and they have no stings¹⁵.

Workers have the most complicated life-cycle. They start work soon after emerging from their cell and they progress from one job to another as their anatomy changes and develops. Their first task is to clean the cell they've just vacated, ready to receive the next egg. Then they feed larvae. There seems to be some confusion about the order of feeding:

...they feed young larvae at first, when their brood food glands are working well. Older larvae are fed when the glands reach a later stage of development.

- Adrian and Claire Waring

- Teach Yourself Beekeeping

...when about three days old, she will feed older brood on pollen and nectar and when her hypopharyngeal glands develop she will feed the younger brood.

- Alan Campion

- Bees at the Bottom of the Garden

As they get more mature, their wax glands develop and they start capping cells and making comb. And so they progress, carrying out various 'house-keeping' duties such as cleaning, fanning, receipt of nectar and more specialist tasks, such as guarding the entrance against invaders and removing the corpses of their worn out sisters. At about three weeks, they start to fly and forage. They may also be employed in scouting for new nectar sources. Scouts that find a new food source, return to the hive to tell the workers by performing the famous 'waggle dance'.

The life spans of worker bees can vary enormously, depending on whether they're 'summer bees' or 'winter bees'. Summer bees live about six weeks. Bees emerging from their cells from August can adopt a different diet with a much higher proportion of pollen. These will be winter bees: bees that can live through the winter. They differ physically from summer bees, storing fat in their abdomens and maintaining their feeding glands (normally functioning only in young workers) so that they can feed the young hatching in the following season.

Leaf-cutter bees

Sweat bees

Stingless bees

Vulture bees

Fairly recently (1982) carnivorous bees¹⁶ - related to the American stingless bees - were discovered. People speculated, of course, about how such a diet could have evolved in a type of insect that was believed, up until that time, to feed exclusively on floral products.

The diet of most bees, most of the time, is limited to pollen and honey. But they can and do, from time to time, eat something more 'meaty'. If a honeybee queen is laying diploid drone eggs¹⁷, for example, the workers recognise them as a nuisance and tackle the problem by eating the larvae. So even honeybees have mouthparts and digestive systems that are capable of coping with this type of food.

Vulture bees, like blow flies, are attracted to rotting flesh. But like honeybees, they collect fluid in their crop and return with this harvest to their nest. The difference is that instead of nectar, the fluid is a grisly combination of the bees' saliva and the liquor that seeps from the corpses upon which they feed. The vulture bee colonies treat this nutritious substance in a similar way to nectar/honey: adding digestive enzymes to change it to a sticky brown storable liquid. They also 'inoculate' it with several species of Bacillus that help to convert the protein to a form that can be metabolised by their larvae. Antibiotics preserve it so that it can be stored for a long time in conditions of tropical heat. So it's just like honey, only horrible.