Honey Bee Anatomy & Physiology

A talk by David Charles of West Pennard, Glastonbury, Somerset

Date: Thursday 26 February 2004

Venue: Church Rooms, Stow on the Wold

Notes by Jeremy Voaden

Honey Bees - Social Insects

The majority of insects are solitary creatures. E.g. Beetles, flies etc. Some, however have evolved to live in communities and their lives are governed according to the needs of a colony. Bees, ants, wasps and termites are the most highly evolved social insects.

Such a way of life requires versatility. Just as communities of humans require cleaners, parents, teachers and farmers, so within the bee colony there are a multitude of tasks to perform.

Further, the bee requires a variety of body parts to complete these tasks.

Different functions are fulfilled by the three types of bee:

Ø Queen

Ø Worker

Ø Drone

It is not really possible to put the three in order of “importance”. They all have vital functions without which the colony would perish.

Generic features of Honey Bees

Bees’ bodies are divided into three parts: Head, Thorax and Abdomen. The wings and legs are joined to the thorax.

All bees and wasps have two pairs of wings that join together in flight but fold away over the back to

i. Avoid getting damaged in flight

ii. Enable them to put their heads deep into the cells

Bees have an exoskeleton i.e.They are hard outside and soft in the middle. The exoskeleton is made of 3 or 4 layers of chitin.

The thorax contains lots of indirect flight muscles for the wings and legs. If a wasp scavenges a dead bee, it will bite off the head and abdomen and carry away the thorax to feed its’ young.

The Queen Bee

Shakespeare originally described the Queen as an “Emperor” until corrected about her gender. She is designed with two principal functions.

The first is to lay a vast quantity of eggs. A good Queen will lay a single egg at the base of each cell. The egg is white, c.2mm long and will grow into a C-shaped, shiny, moist larvae. The Queen has a large abdomen. Within the abdomen are her ovaries. From these, the oviduct leads to the spermatheca where the egg gets fertilised. Each ovary is made up of 120-150 strands (ovarioles). Worker bees retain vestigial ovaries but these only have a few ovarioles which sometimes develop if the colony becomes queenless resulting in a “laying worker”. This is usually “diagnosed” by the presence of large numbers of eggs in single cells.

The second key function of the Queen is to give off a pheremone known as “Queen substance”. Whilst the workers groom and clean her, their craving for this substance is satiated. This pheremone has a cohesive effect on the colony.

The Worker Bee

The workers’ body needs to be built to forage, work within the confines of the hive, guard and undertake a host of additional tasks.

Within the hive they will feed the young, seal the brood, produce wax and draw out cells, receive nectar from returning foragers……

Once nectar is inside the hive, it is processed into honey. Water is evaporated from it until the water content is between 15-17% then the workers seal it over.

Wax production

Wasps have to chew at fenceposts and trees to make their papier-mache to construct their nests. Bees make their own building material – Wax. This is produced from underneath their abdomens from four wax mirrors. The bees catch the wax produced with their hind legs, pass it up to the middle and then front legs then, using their mouth parts, working as a team, mould the wax into cappings etc.

Hairs

The hairs on the abdomen, legs, thorax, head….indeed all over the bees’ body are an essential tool in the pollination of flowers. The collecting of nectar is thus of mutual benefit to plant and bee. It is really useful for the beekeeper to remember that the bee is here to fulfill its’ symbiotic relationship with flowering plants, not to produce honey for humans. Both bees and flowers have evolved as a partnership thus enabling pollination in a large proportion of flowering plants. For humans however, the value of the bees in bringing about cross-pollination of fruit is huge and they should be credited with increasing world food supply by a not inconsiderable amount.

Food sharing and the Proboscis

Many beekeepers will have seen bees with their tongues out, sharing food. Sometimes, when you find a swarm that has been out of the hive for a long time, it appears moribund or to be dying. Spray it with a little sugar solution. The bees sprayed will revive then pass the solution to each other with their tongues. Food sharing is an essential part of the success of the honey bee colony.

It is the older workers who are the foragers. When the weather is good, the foragers don’t go into the far reaches of the hive to store the nectar. They pass it on to worker receivers at the hive entrance who then take in to the stores. This increases the forager “turn around time”.

The Queen and Drone bees have short tongues. However, the worker has a long tongue to reach down into the flower and access the nectar. The correct name for the tongue is the Proboscis. If this is opened up, it comprises three parts – the labellum probes, glossa and paraglossa. The nectar goes up between the three.

Foraging anatomy & physiology

Worker bees forage for:

Ø Nectar

Ø Pollen

Ø Propolis

Ø Water

Nectar is stored in the “honey stomach” which is in the abdomen.

On each hind leg, the worker has a “pollen sack”. The bee rubs its’ back legs together to compact the pollen it has collected down into the “sack”.

The front leg of the bee has a notch at the top of the tarsus of each of the front legs that it uses to clean the antennae.

The middle leg of the bee has a spike or spine to help pass up wax cells.

The back leg is the most interesting leg. This has rows of little brushes called pollen combs which are used to pass pollen up the leg. As it makes this journey, the pollen is moistened with a bit of nectar so the bee can knead it into a pellet and then place it on a spike that we call the "pollen sack".

Bees need pollen for their protein so they store it near their brood nest to feed the young. The worker bee storing the pollen puts its’ legs down into the cell and levers the pollen off the spike then another bee will come along and use its’ head to pummel down the pollen compactly into the cell. Over time, the cell fills with layers of different coloured pollens.

Water is especially important for the colony in early spring. The bees dig into their stores as brood rearing starts apace. Some of the stores may have granulated and so a water source is essential.

Only 5-10% of bees actually gather propolis. They carry it on their hind legs in sticky blobs. They use their mandibles to tear off propolis and move it around the hive. It is used to block gaps and embalm invaders such as mice.

The Circulatory System

The circulatory system comprises 5 “simple hearts” in the abdomen which power the bees’ “blood” called haemolymph. The haemolymph is not carried by arteries and veins but flows loosely around the body, controlled by the dorsal and ventral diaphragms. Oxygen enters into the bee via spiracles (including two rows of 6 on the abdomen) thence into trachea and into bellows in the abdomen which distribute it into the haemolymph.

The Acarine Mite can get into the bee via the big spiracle in the T2 section of the thorax. The presence of acarine mites can only be detected by studying the respiratory system where dark brown stains will be found in the tracheal tube.

The Digestive System

The proboscis sucks up nectar into the cibarium (mouth). It then passes into the pharynx and oesophagus then between the indirect flight muscles that control the wings down into the “honey sack”.

The “honey sack” is very flexible and, when full, expands hugely at the top end of the abdomen. At the end of the “honey sack” is the proventriculus. It is the gut beyond the proventriculus that is susceptible to nosema.

Nosema, a small protozoan, attacks the epithelial cells inside the lining of the gut (ventriculus) which shortens the life of the bee. Nosema spores can be clearly seen under a x400 magnification microscope. They look like tiny grains of rice. They are all the same size and structure.

Inside the ventriculus are the malphigian tubes (c.100). These are the bee-equivalent of the human kidneys. The malphigian tubes take out nitrogenous waste from the haemolymph and the waste passes into the rectum. The bowel and rectum can also expand. In winter, bees can store waste material for weeks before going out on a “voiding flight” on a warm day. Husks of pollen grain are common waste content.

The Nervous System

The nervous system comprises a small “brain” and 7 ganglia right down the body. The 7^th is near the end of the abdomen. This is why the detached body part of the bee sting continues to pump venom. The ganglia control the wings, haemolymph, legs etc….

The Glands

Bees have a range of glands that come into use at certain stages of their lives when there are particular tasks to perform.

The earliest glands to be used are those involved in the production of brood food, specifically the hypopharangeal, mandibular, post-cerebral and salivary glands.

The wax glands are essential for drawing out wax.

Workers have a gland at the end of their abdomen. This Nasanoff gland is used by the guard bees at the hive entrance to disseminate a scent that guides young bees back to the entrance during early flights. This has a vinegary scent.

The Drone Bee

The primary function of the drone is to mate. These male bees take up a lot of room and drain the colony resources so they are forced out of the hive in advance of winter.