Another mild week and sunshine send the bees down to the river where they are still collecting Himalayan balsam though ivy is a strong contender for their attention, and huge yellow pollen loads are coming in to all the hives. For various reasons, I have 3 overwintering colonies belonging to friends dotted round the garden. The 2 colonies recently moved down from the edge of the grouse moors think that they are on the French Riviera for their holidays and fly in all weathers when the garden colonies are indoors. As I look out of the window, I see sunlight illuminating golden coruscating wings as Jane’s bees swoop down over the hedge.
I think that even moving a few miles to a lower altitude makes a difference to how the colonies behave. Imagine how confusing and stressful for colonies to be transferred even from one side of Scotland to the other where geography and climate differ so much. For example, in some West Coast areas the bees build up later in the season than over here in preparation for their one and only summer crop. This is due to different weather and forage. Those bees, if moved to the East Coast, will not be ready in time for an oil seed rape crop in April/May in their first years at least. The flip side is if our bees are transferred from East to West, they will be getting ready for a spring nectar flow with too many mouths to feed and they risk starvation if there is no early nectar flow. A strong reason for buying very local bees and not relocating bees to the other end of the country.
Using the observation hive bees as a brood “barometer”, and finding the queen has stopped laying, I’ve been round the colonies with Varrox Eddy vapourising with oxalic acid crystals (Apibioxal). Only 2 of my 9 colonies are having moderately large varroa drops. https://www.beelistener.co.uk/varroa-treatment/vapourising-oxalic-acid-safely-easily/
I’ve added top insulation above the crown board and below the roof using old woollen blankets and jumpers. Susan Jardine gave me a sheep’s fleece which I cut up and sewed inside cotton duvets that I made. Kitta thinks that I should have stuffed the bits of fleece into old jumpers to make them more absorbent. She may be right about that and I will experiment over this winter and report back on my findings.
A farming neighbour is spraying a field with Roundup to clear it for a crop of wheat and grass. This doesn’t fill me with deep joy. I’m not worried about the honey bees so much because they are too busy on ivy to go near this field, but it is not great for other insects given the negative effect on their gut microbiome (and good bacteria) of fungicides and herbicides, according to Dave Goulson in Silent Earth. I’ve found a resource with some information on alternatives to glyphosates. This is an American site but I think it will be mostly relevant and useful to everyone. Safe Roundup Alternatives | Killing Weeds Without Glyphosate (consumernotice.org)
Honey as Currency.
The highlight of this week has been bartering honey for free range farm meat. My good friend Tristan McLennan was here from Glen Orchy on Saturday night with lamb and pork packages which have filled the last space in the freezer. The pork sausages are the tastiest I’ve had for as long as I can remember and I am impressed that they are not very fatty at all. This exercise has made me even more aware of the high value of honey and how satisfying it is to exchange goods like this. Now onto honey bee nutrition and picking up from last week.
Lists of things are not very useful unless we can to relate them to practical situations. We learned last week about vitamins being found in nectar and honey, but what do they do for honey bees? Well, they are essential for normal growth and development and most of them cannot be manufactured by the bee (apart from Vitamin C) and so are obtained from plants via nectar and pollen. However, in the intestine of the honey bee there are bacteria and yeasts which form the gut microbiome. The gut microbiome is really important and receiving a lot of scientific attention and research at the moment. Some vitamins are produced in the gut by bacteria and yeasts, but if the bee is exposed to fungicides encountered in the field on foraging trips they may be harmed. The ingestion of fungicides may damage the gut microbiome and affect vitamin production as well as other functions.
Vitamins are needed for enzymes to function and act as catalysts in chemical reactions. Enzymes are catalytic proteins. In the conversion of sucrose to glucose and fructose an enzyme is required to speed up the process. It is possible for a solution of sucrose in water to spontaneously hydrolyse very slowly over time to give glucose and fructose. Experiments with a solution of sucrose in sterile water show that it will sit for years with no noticeable hydrolysis. However, if a small amount of sucrase is added, the conversion takes place very quickly to produce glucose and fructose 1.
Vitamins such as the B Complex and Vitamin C are water soluble and very important for honey bees. They are mostly obtained from plants via pollen, but some Vitamin C is manufactured inside the bee by the microorganisms known collectively as the gut microbiome.
Interestingly, the fat-soluble vitamins such as A D K & E are not considered essential for honey bees, though when they were fed these experimentally the amount of brood produced increased. Vitamins are more important for brood development so younger worker bees need them more than older field bees to produce brood food, especially royal jelly. So, the Vitamin B Complex is key to pharyngeal gland development.
Vitamin B Complex.
Let’s break the B Complex down to component parts to review their roles: Thiamine (B 1) is required by enzymes to release energy from the sugars and amino acids. Riboflavin (B 2) functions in brood food production. Niacin (B 3) is needed by the enzymes that release energy from fats during fat/lipid metabolism. Pyridoxine (B 6) is required for larval development.
The conversion of nectar to honey involves both chemical and physical processes. During the chemical processes enzymes speed up reactions by working on specific substances so there are many enzymes and I shall only mention the most important ones. For example, sucrase only acts on sucrose but not maltose which is broken down by maltase.
So, how do these substances like sucrose actually break down to form other substances? Atoms in substances such as sucrose are bonded by strong forces of attraction which hold them together in molecules. Energy is required to break up the bond and it is also produced during the formation of new bonds. What happens is, the molecules held together in the tight bonds absorb heat from the surroundings and become unstable. Heat forces the molecules apart and as they absorb more energy the molecules move faster and faster bumping into each other until the bond breaks. Enzymes allow these reactions to speed up by lowering the level of heat energy needed to break the bonds. If too much heat were added the enzyme proteins would be degraded. All organisms must use an enzyme catalyst that permits the making and breaking of bonds to happen at moderate temperatures since high temperatures kill body cells.
Converting Nectar to Honey.
Although the honey bee crop/honey stomach can hold around 100 mg nectar, most foragers carry home around 15-40 mg of nectar. Some of this is used immediately by the forager for flight fuel, so a little amount passes through the proventricular valve from the crop into the mid-gut or ventriculus from where it passes into the haemolymph and provides instant energy. Sucrase begins to act on sucrose on the journey back to the hive and other lesser sugars are broken down by specific enzymes. The nectar is passed over via trophallaxis to the house bee who continues converting nectar to honey.
Here is the chemical equation showing the hydrolysis of Sucrose:
Sucrose (C 12 H 22 O11) + H2O + Sucrase = Glucose (C 6 H 12 O 6) + Fructose (C 6 H 12 O 6).
The other important enzymes in honey are diastase and glucose oxidase. Diastase is also produced by plants, but in honey bees it is secreted by the hypopharyngeal glands and it breaks down starches into sugars and is involved with the digestion of pollen. Like sucrase and other enzymes, it is sensitive to heat but more easily destroyed than other enzymes, so low levels of diastase in honey can tell us that is has been overheated. The acceptable level of diastase in honey is not less than 8 unless the honey is false acacia (Robinia pseudoacacia) which has a naturally low level of diastase of not less than 3. Acacia honey is very pale, fructose dominant and slow to granulate.
Glucose oxidase is also secreted by the hypopharyngeal glands of the young worker bee and is an important part of the ripening process because it acts on diluted honey with high water content and reduces the risk of bacterial growth and fermentation. Following another chemical reaction gluconic acid and hydrogen peroxide are produced making the honey more acid and less favourable an environment for bacteria to thrive. The pH of honey is around 3.9 which gives it a sharp taste but enhances the flavour.
The conversion to honey also involves the physical processes of reducing the water content so that it is less than 20% water, unless heather honey when UK Honey Regulations permit a level of less than 23%. In the US the regulations state that the water content of honey must be less than 18% which may have something to do with a different climate?
The next stage of reducing water content is carried out by the middle aged house bee through regurgitating droplets of nectar which when exposed to the air (on their proboscises/tongues) evaporates water. They also fan at the hive entrance to get rid of humid air and circulate fresh air. Nectar is hung up to dry in empty cells above the storage cells till it is ready to be packed and sealed in the honey comb.
Campbell, N.A., Reece, J.B., 2002, Biology Sixth Edition, Benjamin Cummings, San Fransisco.