Endocrine System of the Honey Bee
Scientific Beekeeping
Scientific Beekeeping
Endocrine glands in all animals secrete their substances internally into their blood or haemolymph.. Humans have a complicated system of endocrine glands including the thyroid gland, pituitary gland, adrenal glands and ovaries or testes.

The bee's system, as we understand it at present, is somewhat simpler:

1. Pars Intercerebralis: The neuro-secretory cells within the pars cerebralis are connected to the Corpora Cardiaca and are larger in the worker than queen or drone.

2. Corpora Cardiaca: A pair of glands, slightly smaller than the corpora allata which sit superior and medial to the latter. They stimulate the prothoracic glands to secrete ecdysone and thus promotes ecdysis.

3. Pro-thoracic Glands: This reticulate gland is attached to the intestinal tract at the junction of the esophagus and midgut of the larva or pupa. It secretes the hormone Ecdysone which is only found in the larval and pupal stages of development. It causes shedding of the Cuticle. It is prompted to produce ecdysone by stimulation from the Corpora Cardiaca.

4. Corpora Allata: A pair of glands sitting either side of the aorta, behind the brain. It produces Juvenile Hormone which, in the larva or pupa, holds back ecdysis and in the adult bee retards moving on to its next function. It is important in caste determination. Juvenile Hormone production is seen to peak in larval stages, particularly in queens where it is believed to have a substantial role in caste specific organ differentiation, particularly ovaries.

As an adult the JH titre stays at low levels throughout a queen's adult life cycle. In young workers, the hemolymph JH levels are low, as these bees perform in nest tasks, primarily feeding the brood with secretions from their well developed hypopharyngeal glands. As the bees grow older and switch to performing more hazardous tasks foraging, outside the nest, their JH titres increase.

5. Although vitellogenin is strictlty a food (containing all the three main food elements of carbohydrates, fats and proetins, glycolipoproetin) and not a hormone it is antagonistic to Juvenile Hormone in the adult bee. Its presence is inversely proportional to JH. Vitellogenin is found in winter bees where a longer life span is required so JH will be low.

6. Octopamine is found in the nervous tissue of the honey bee and is closely related to Norepinephrine a stress hormone found in man. It effects several functions in the honey bee.
Diagram showing a slice through the head, seen from behind. In the small space behind the brain and in front of the connection to the neck are the main neurosecretory glands: corpora allata and corpora cardiaca. Understanding Bee Anatomy, Stell (2012). (see item to the right)
In a 2003 paper about Juvenile hormone and division of labour (see above link) the researchers discovered that bees whose corpora allata had been removed had a significantly reduced metabolic rate. further it caused flight impairment. Of those that were able to take off they had a slower ground speed but range was unaffected. It was concluded this was due to inadequate development and/or function.

Allatectomised bees also flew earlier than the control bees.
Juvenile hormone and division of labor in honey bee colonies: effects of allatectomy on flight behavior and metabolism
The diagram above is from a paper written in 2011 (see link to the left of diagram for full text) illustrating the parts of the nervous system that Octopamine is found:
"Schematic drawing of AmOA1 immunoreactive neurons and processes in the brain and subesophageal ganglion of the bee made from confocal images of agarose sections of bee brain stained with anti-AmOA1 antibodies.
The right hemisphere shows a frontal view of the bee brain with the optic lobe neuropils (Re, retina; La, lamina; Lo, lobula), antennal lobe (al) and summarized mushroom body neuropil; the left hemisphere of the brain shows a more posterior frontal view at the level of the dorsal lobe (dl), pedunculus (ped) and calyces of the mushroom bodies. AN, antennal nerve; DG, dorsal group of antennal lobe neurons; LG, lateral group of antennal lobe neurons; MDG, medial group of antennal lobe neurons. Some neurons that express the AmOA1 receptor could be identified as: 1, PCT (or feedback neuron group); 2, lobula and medulla mushroom body neurons. The cells in this cluster have fibers in the anterior superior optical tract (asot). The arrow shows axons (only the ending of the tract) from these neurons as they enter the medulla serpentine layer. A few AmOA1 positive fibers enter through the lobula optical tract (lot) that connects the lobula and mushroom bodies.; 3, photoreceptor cells in the retina; 4, monopolar cell bodies in the lamina; 5, medulla columnar neurons; 6, photoreceptor cells in the ocelli; 7, a median group of subesophageal intrinsic neurons; 8, ellipsoid body neurons, 9, a group of median neurosecretory cells (MNC) in the pars intercerebralis. Abbreviations: K, Kenyon cell bodies; Ca, calyx of the mushroom bodies; o.w.br, the outer wedge of the basal ring; co, collar; br, basal ring; ped, pedunculus; vl, vertical lobe of the mushroom bodies; ml, medial lobe of the mushroom bodies; γ, gamma lobe of the mushroom bodies; PCT, protocerebral-calycal tract; EB, ellipsoid body; FB, fanshaped body; o.Me, outer medulla; i. Me, inner Medulla; es, esophagus; SEG, subesophageal ganglion."
Distribution of the Octopamine Receptor AmOA1 in the Honey Bee Brain
Jackie Elliott