If you’re a beekeeper, you probably think about sugar a lot, whether you know it or not. Science writer Dave Black takes a deep dive into the honey bee’s relationship to sugar, the various types, and how there is more to nectar than what you might think.
By Dave Black
Biologists talk about four essential types of ‘molecules for life’: proteins, carbohydrates, lipids and nucleic acids. Beekeepers think about carbohydrates a lot.
Sugar is the generic name we use to describe soluble carbohydrates, or ‘saccharides’. Insoluble carbohydrates are dubbed polysaccharides and, being large and insoluble, are frequently used for their structural properties – the exoskeleton of the bee is actually made with the polysaccharide chitin, derived from glucose.
The soluble saccharides, that we call sugar, are generally used to provide energy for getting around, to power the chemical reactions that make bees tick, or turned into a form (like a lipid) that allows them to be stored to use later.
The ‘sugar’ bees use, either collected from nectar or fed to them directly, is mostly a mixture of three sugars, sucrose, glucose, and fructose, but they can use others. Sucrose is a di-saccharide, because it’s made of glucose and fructose mono-saccharides joined together. Scientists, being an orderly lot, give sugars names ending in -ose so they are easy to spot.
Bees use a lot of sugar [1] [2] [3]. The best estimates we have suggest that a resting bee will use a little less than 1.0mg/hr and a flying bee will use 10-14mg/hr. When you start to do the arithmetic for 20,000-60,000 bees, for 365 days, you can arrive at budgets in the order of 300-400kgs of syrup/nectar that bees will need to sustain themselves in a year[4], and that’s without allowing for your 10%.
The natural source of sugar for bees is plant nectar and/or insect honeydew. There are some significant differences between these, as well as considerable variation within each source. Sugars that bees are understood to use are glucose, fructose, sucrose, trehalose, maltose, and melezitose, but floral nectar is known to contain at least 37 different sugars[5] [6] and an abundance of other things[7], all both good and bad for bees. Nectar has a lot of things going on. It’s provided as a food for fortunate allies, but it must be defended from thieves[8], and if it becomes contaminated by something, the plant has to protect itself. Besides chemistry, there’s a whole microbiome in nectar[9].
It is important to recognise that it is not just a sugar solution. The quantity of the three main sugars (glucose, fructose, and sucrose) in nectar is pretty consistent for a single species of plant, but the total sugar concentration can vary from 8%-80% (20%-30% is probably the most common) across species and this can be almost all sucrose (like avocado) or nearly all glucose with fructose (rata is notable for its glucose content). The rest isn’t just water. Lipids can be present in high enough amounts to be visible: the nectar from jacaranda flowers appears slightly milky because of the lipids in it.
There are also small quantities of amino acids and proteins, vitamins, hormones, alkaloids, phenolics, terpenoids, metal ions, and of course many more sugars: some, if not sufficiently dilute, can be toxic[10]. For now, we don’t understand either the dietary significance of all the constituents of nectar, or their ecological implications for floral visitation or pollination. However, we do understand that we cannot completely replace nectar or honey with manufactured sugar solutions, and there are instances when nectar and honeydew are not perfect bee foods either.
Dave Black is a Bay of Plenty based hobbyist beekeeper who now works in the kiwifruit industry. He has a degree in Environmental Science and for the past 25 years he has been reading and writing about bees and beekeeping. His essays are available at www.beyondbeebooks.substack.com/
