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Propolising Behaviour in Honey Bees

There are several reasons that cause bees to propolise.
Covering up or encapsulating unwanted odours from a surface or material.

Surface finish or more correctly the porosity of the surface concerned.

Filling a gap caused by the proximity of two objects, with an air space (or open space) behind.

Filling a crevice that does not have links to the open air.

Propolis is used to stiffen and strengthen the combs after initial construction.

Filling a void... There is not much difference between filling a gap and filling a void, I make the distinction that a gap is less than a single bee space and a void is more than a double bee space.

Dampening of vibration is the reason that I think is most often overlooked.

The "varnishing" of wooden parts with propolis is not universal, it has two causes... One is a response to the surface texture and is considered a "mechanical" response ie. filling the cavities in a coarse surface. A smoothly machined (planed) surface does not attract the propolising.

The bees will propolise timber from particular species of trees, regardless of the surface texture... One notable type of wood being Western Red Cedar (often used in hive manufacture) this wood has long term aromatic retention and it is thought that this is in some way disliked by the bees. It is not likely that any varnishing of Western Red Cedar is for hygiene purposes, as it is itself highly sterile and anti fungal.

There are some types of wood that attract very heavy deposits of propolis. For example, I had a hive that was quite nasty and so I re-queened it. After this first requeening failed to quell the anger, I picked up the entire hive and barrowed it about 5 metres away from its's original site. I then put a fresh stand, floor and new brood box on the original site. Using a traveling box, I then fetched 5 frames at a time from the original hive and placed them individually in the fresh hive, inspecting each one of them thoroughly. I eventually found that three of the frames had bunches of bees on the sidebars and that these sidebars were very heavily propolised, there was also no brood within 100 mm or so of the sidebars in question. I placed these frames in an another traveling box and completed the transfer, frame by frame. After I had buttoned up the colony I shook all the bees off the affected frames and took them back to my workshop.

The sidebars concerned had been made from an unusual species of timber that I never did identify (we used all sorts of rare woods in another part of the business).

The thick propolising made me realise that the bees did not like it for some reason. I was surprised by the thickness of propolis build up (it was around 6 mm thick mostly). My surprise was due to the fact that I thought the propolis film would have been air tight and the application of a thin continuous covering would have sealed in whatever it was that the bees found repugnant.

Surface finish
In an Email Discussion on the Norland List... Joe Waggle mentioned a colony that used much propolis.

I asked "Do they put coin shaped dollops near the ends of the top bars?"

Joe Replied "I have seen dark round hard dollops on the top bars in Italian hives."

My next mail "In the intervening 24 hours between these two messages, I have been thinking about this and there is something about it that I do not understand.

OK the race of bees in my case was mongrel with a high percentage of Italian, but I am not concerned about any racial linkage. I wish to explore the 'why'... One thing that I remember (I have not observed this dollop behaviour for about 15 years) is that the dollops were reasonably regular in size and were placed about the same distance from each end of each top bar. The dollops looked as if they had been 'poured' into position, more or less circular, but wobbly at the edges.

It is this straight placement that is rankling in my mind... What governs the positioning? If it were the limits of the nest the rows of dollops would be curved or at least bend inwards at the ends.

The obvious thing is that the inner face of the box is parallel to such placement, but that still begs the question as to what the relationship is between dollops and box."

Another post from me "I think I have found the answer to this, but I must ask a question first... How far from the end of the top bar was the centre of your dollops Joe?"
Joe's answer... " An inch (25 mm) or so."

My conclusion... "Now my dollops were about 40 mm (just over 1 1/2") from the end of the bars...

This is the clincher, not backed up by any research, just logic.

In USA with Langstroth frames the lug is 3/4" (19 mm) long, in UK the lug is 1 1/2" (38 mm) long.

Immediately after the lug, the end grain of the side bars occurs in two places where the bridle joint comes up to the top surface. In both UK & USA the sidebars are 9 mm or 3/8" thick.

End grain is often much more propolised than surfaces that are smooth and 'with the grain'.

I reckon that the dollops develop when strains of bee that are extra heavy propolisers, plaster the end grain of these nominal 9 mm x 6 mm rectangles and that the build up is so high that the two patches become one. This resulting dollop is added to and becomes round (or nearly so).

The above fits the facts so well that I favour it as being correct. Can anyone shoot it down?"

Gaps and crevices are similar in some respects, a gap or crevice is too small for a bee to enter and so is wasted space that could harbour disease or parasites so any response that fills these with propolis or other material (wax is sometimes used or is alloyed with propolis) will be beneficial to health and provides natural selection pressure for the behaviour.

Freshly drawn comb, is totally white in colour and contains nothing but beeswax, no residue being left after melting or dissolution in carbon disulphide (carbon disulfide). The bees will add a small amount of propolis onto the surface of the thickened cell rim once the cell is drawn to full depth. This adds red or brown colour to the basically white comb. This addition increases the strength and stiffness of the comb.

Voids are more often filled with burr comb, but propolis is sometimes used. An entrance that is larger than the bees desire will be reduced in size, but there is a difference in the material used according to the amount of reduction required. An entrance that is only reduced by a small amount will mainly be propolised, but a much larger one may be reduced using wax. An example of this was a hive knocked over by vandals so that the combs were standing on one end with both the major openings exposed. The bees built thin sheets of wax (roughly 1 mm to 2 mm thick) over all but a very small area of these large openings. The wax was a light khaki colour which probably indicates admixture of propolis, fresh wax and wax recovered from unused cells.

Bees in hives will use propolis to seal unwanted draughts and possibly to modify the shape and size of the entrance.

The vibration is in two forms... Large vibrations caused by animals passing by, or earth quakes. Small and more subtle vibrations caused by thermal expansion/contraction of the hive structure or it's supports and perhaps infrasound communication between Elephants (in regions where they exist).

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Originated... 07 December 2001, Written... 14 October 2002, Corrected... 09February 2003,