Have you ever watched a honey bee with its glossa (tongue) stretched out collecting nectar from a flower and wondered how it all happens? It’s an amazing sight and you can be forgiven for not noticing how just hairy its tongue is. You really need to examine the mouthparts under a microscope to fully appreciate this. There are around 3,000 bristles on the glossa and they function to assist the bee lapping up fluids by trapping them in the hairs.
Mouthparts.
Honey bee mouthparts comprise one pair of jaws or mandibles, and a hairy proboscis or tongue. This might sound simple but the reality is far from it! The proboscis is like a Swiss army knife with lots of fold-away parts which unpack to form a straw-like sucking system comprising parts of the maxillae and labium. The tubular food canal is formed by the paired galea and labial palps. These four structures come together and close around the glossa to form a tube, and, together with the glossa they form the proboscis. With the aid of muscles and a suction pump, nectar is sucked up into the cibarium which is the functioning mouth. From there fluids enter the pharynx, which is a tube continuous with the cibarium, and on through the oesophagus and into the honey crop/sac.
The mandibles have several different uses and an important one is stabilising the proboscis by holding it firmly in place during feeding. When feeding finishes and not in use, the proboscis is folded backwards behind the mandibles and held in position by the upper lip or labrum which is brought down against the mandibles. All the moveable parts are disassembled and folded away like tent poles till next time, but in this case the proboscis lies in the mouth cavity in a Z-shaped pattern.
Most nectar collecting insects either lap or suck to remove nectar from flowers. We have known for a long time that honey bees lap up fluids by dipping their hairy tongues in and out of them rapidly to draw fluids into their mouths. Recent research shows how they can also suck up fluids, and how amazing honey bees are in that they can do both, and even switch between these modes during one feed as sugar concentration changes. The glossal hairs stand erect and trap nectar which is then sucked up into the cibarium. If you examine the flabellum, at the end of the glossa, under a microscope, you will notice a spoon- shaped hair depression which is ideal for holding nectar. You will also notice a groove running down the glossa and this two-way canal is used to suck up nectar and water. It also allows saliva to flow down from the salivary glands to dilute stores, add enzymes to nectar, and prepare pollen for carrying home.
Some interesting recent research by Wei and colleagues 1 shows how honey bees lap or suck depending upon the concentration of the nectar or sugar solution. When the sugar concentration is low they suck, and when concentration is high they lap making honey bees very efficient feeders. What is also remarkable is that they can switch modes easily, and this flexibility means that they can utilise a wide range of forage plants and energy sources.
Using electron scanning microscopes, scientists made further discoveries2 that revealed how the tongue can be such a versatile tool by being both rigid and flexible. The tongue can extend to probe the corolla of a flower and then retract with the thousands of glossal hairs still erect and holding the nectar for uploading. Using such powerful microscopy made it possible to see that the glossal hairs are supported by rigid ring-like bases. The hair bases are embedded in an elastic and resilient intersegmental membrane which make honey bee tongues both rigid and flexible.
Next time you watch a bee on a flower or water source Ihope you can enjoy it more knowing what’s going on inside that complicated little animal.
Coming UP Soon.
Look out for more on mandibles in a couple of weeks (you can subscribe for free to beelistener and receive weekly blog announcements). Tune in next week to find out how a Dundee school set up its own beekeeping association and training apiary under the leadership of beekeeper Fred Mollison.
References:
1Jiangkun Wei, Zixin Huo, Stanislav N. Gorb, Alejandro Rico-Guevara, Zhigang Wu
Jianing Wu, Sucking or lapping: facultative feeding mechanisms in honeybees (Apis mellifera) Published:12 August 2020https://doi.org/10.1098/rsbl.2020.0449
2Yu Sun Junrong Zhang, Xiaoyang Tang, Zhigang Wu, Stanislav N Gorb , Jianing Wu . (2021) Specialized morphology and material properties make a honey bee tongue both extendible and structurally stable, doi: 10.1016/j.actbio.2021.09.045. Epub 2021 Sep 28.
Burlew, R., (2021) Hey Bee, Stick Out Your Tongue and Say “Ahh”, American Bee Journal, October 2021, p 1095-1097.
Goodman, L., (2003) Form and Function in the Honey Bee, IBRA, Cardiff.
Mattingly, R.L., (2012) Honey-Maker-How the Honey Bee Worker Does What She Does, Beargrass Press, Portland, Oregon.
Snodgrass, R.E., (1956) Anatomy of The Honey Bee, Comstock Publishing Associates, Ithaca and London.
Stell, I., ((2012) Understanding Bee Anatomy, The Catford Press.
Winston, M.L., (1987) The Biology of the Honey Bee, Harvard University Press.
It’s amazing anyway, the anatomy in general but even more so when knowledge is increased by research – just shows that every day you learn something new (Wu 2020)- jaw dropping!
Hello again, Jane. Good to know that you appreciate the science behind the information. Thank you for commenting. It makes all the digging about for new knowledge worthwhile.
Ann.
Having just taken delivery of a microscope, I can’t wait to explore and identify on a honeybee, for real! The colour-coded images are just perfect – so helpful. As is usual after reading your blog, I close the lid of my laptop in awe and wonder! Thank you Ann.
That is very exciting and I wish you lots of fun adventures with your microscopes, Liz. I’m glad you found the blog helpful and thank you for commenting on it. I hope that mandible blog helps too and that tomorrow’s exam is fair and that you sail through it. Best wishes, Ann.