As I write, it’s early spring – just on the cusp. The nights are still cold and although there are plenty of pollen bearing plants and shrubs, there is very little nectar. The hives still have fondant over their brood boxes.
In beekeeping there are so many questions, not only for a relatively new beekeeper, like myself, but for more experienced beekeepers too. That’s why I find beekeeping so fulfilling – it’s the hobby that keeps on giving – a continuous adventure.
The question that has been floating in my mind and only half answered is – ‘What do bees eat?’
OK , simplistically I can say ‘pollen’, ‘bee bread’, ‘honey’, ‘nectar’ and ‘royal jelly’, plus I know they need water. But it’s more interesting than that and it’s right ‘on trend’ – being a case of ‘you are what you eat’. With the same ingredients, bees can grow a queen, a worker or a drone – it’s the proportion and quantity of each that makes the difference.
First of all, Royal Jelly; this is produced by the hypopharangeal and mandibular glands. The hypopharangeal glands provide a clear fluid rich in enzymes, lipids, vitamins and proteins. When young bees emerge from their cells, the hypopharangeal glands are still developing. The young bees need a pollen rich diet for 7 – 10 days to complete the development of the hypopharangeal glands and produce their component of royal jelly. The mandibular glands also develop in the young bee and then produce the milky component of royal jelly, rich in lipids including the fatty acid 10-hydroxy-2-decanoic acid. Together, the secretions from each gland produce royal jelly. The average moisture content of royal jelly is 60-70%, crude protein 12-15%, total sugar 10-16%, lipids 3-6%, vitamins, salts and free amino acids.
Nectar is a dilute sugar solution produced by the nectaries of plants, containing the disaccharide, sucrose, and two monosaccharies, glucose and fructose. The water content of nectar can vary from 90% to 50% approximately. It can also contain small quantities of phytochemicals; amino acids and volatiles.
Honey; Foragers collect nectar and store it in their honey stomachs. Some may be digested by the individual bee to provide energy and to the rest they add enzymes (invertase, glucose oxidase) which begins the process of making honey. Invertase converts sucrose into glucose and fructose. A small amount of the glucose is attacked by the enzyme, glucose oxidase, and is converted into gluconic acid and hydrogen peroxide. Gluconic acid makes honey acidic, and hydrogen peroxide has germ-killing properties.
Hive bees recieve nectar from foragers and pass it between many individuals to reduce the water content of the nectar. To do this they either form a large drop between the proboscis and the mandibles to allow evaporation, or deposit it into cells and fan over it. The moisture has to be reduced to 17-18% before bees consider the honey “ripe” and then seal the cells. Some of the nectar is used immediately in feeding the brood.
Pollen contains proteins, amino acids, vitamins, fats and sterols. Pollens vary from 10 – 36% in protein content. Bees also require 10 amino acids from pollen sources. Not all pollens contain all 10 amino acids, so collection from a range of pollen sources is beneficial to bees. Rape/Canolla pollen, for instance, does contain all 10 amino acids, but the quantity of some of these does not reach the bees nutritional requirement. Dandelion pollen does not contain all 10 amino acids. The amino acids are the building blocks for proteins.
The 10 essential amino acids for bees are; Threonine, Valine, Methionine, Leucine, Iso-Leucine, Phenylalanine, Lysine, Histidine, Arginine and Tryptophan.
Bee Bread – Bees prefer to feed on fresh pollen, but they also preserve this important protein resource as ‘bee bread’. This is the pickle in their larder. A bee backs into a cell, kicks off it’s pollen load, then other bees ram it in with their heads and add small amounts of honey or nectar and glandular secretions. When it’s 2/3rds full they place honey on top and leave it to ferment. Bees digestive systems contain beneficial bacteria, notably Lactobacillus Kunkeei. Bees practise ‘zymurgy’- the art of biochemical fermentation; Lactobacillus Kunkeei seemingly thrive in fructose rich aerobic and anaerobic conditions, so packed in with a mix of pollen grains and honey, they happily reproduce, eliminating lactic acid as a waste product. This is the vinegar in the pickle and acts as a preservative. Like any pickle in the larder, its quality deteriorates with time.
Bees, like some humans, could be said to have a ‘sweet tooth’. Larvae destined to be queens will be supplied with Royal Jelly that has a 34% sugar content – mainly glucose. This stimulates the larvae to eat more (40% more than worker larvae 6 days after hatching). In the first 3 days, the milky looking Royal Jelly is mostly supplied by the mandibular glands. From day 4-5 it is mostly provided by the hypopharangeal gland. The queen larvae have an excess of royal jelly supplied, even up to capping, but strictly no pollen. Larvae destined to be workers are progressively fed a changing diet. The Royal Jelly has a 2:9:3 ratio of mandibular secretion; hypopharangel secretion; pollen. It contains approximately 12% sugars. Since it differs from the constitution of Royal Jelly given to queen larvae, it is often called Worker Jelly. However, Worker Jelly is only fed to larvae for the first 3 days and then the protein and lipid content goes up while the glucose content goes down (moving to predominantely fructose). It is modified by additions of honey and pollen. Drone larvae hatch from unfertilized eggs so are identified by nurses as male, occupying lager cells on the comb. Drones have different protein and sugar requirements than workers. The investment of nurses to raise an individual drone larva far exceeds that for a worker larva. There is less known about Drone larval food, but It starts the same, with secretions from the hypopharangeal and mandibular glands. There are significant amounts of sugars fed in the first 3 days which drop by 50% over this time. High quantities of low grade pollen are then fed to drones. There is roughly X4 by weight of food fed to drones compared to workers
So finally, summing up; the effect of different feeding regimes and their outcomes in fertilised larvae (potential queen or worker from the same type of larvae) is a type of epigenetics called ‘phenotypic polymorphism’ – you are what you eat – especially if you are a bee!