The Hollow Tree Experiment
By Ian Rumsey

(c) Copyright Ian Rumsey
Reproduced on by permission. 
Ian Rumsey


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Varroa arrived in Essex during 1996 and the winter of 1997/8 brought devastation to beekeepers in the area.

From my swarm collecting activities it was apparent that wild bee colonies had not suffered, also one of my own colonies survived in a home made hive, which developed into the 'Hollow Tree' experiment.

To investigate this situation further I wrote to local newspapers in England and Wales requesting information regarding wild bee colonies and received over 100 reports.

This led me to believe that the breed of bee was unimportant and perhaps the habitat and environment were deciding factors.

In 1998 I collected two swarms and placed them in 'HT' hives 8 & 16, numbered the 1997 'HT ' hive No 4, and commenced a weekly varroa drop count on all three in May.

During 1999 I continued with the varroa drop count for hives 4,8,& 16 and housed and monitored a further 4 swarms in 'HT' hives 1,3,6,& 12.

From these results I have made the following observations­

(1). Bees naturally groom themselves free of the varroa mite.

(2).The 'HT' hive does not allow groomed varroa mites to rejoin the colony

(3).Bees naturally uncap cells containing unhealthy brood and remove the contents,

(4).There are two limiting factors preventing uncontrolled varroa increase.
(a).Grooming whilst varroa are outside the cell.
(b).Uncapping whilst varroa are inside the cell.

5). Periods where there is a reduction of brood resulting in excessive numbers of mites. searching for a reducing number of nest sites causes an increase in grooming and cell uncapping due to multiple mite infestation.

(6).The number of varroa bred in a colony is not in direct proportion to the size of the colony.

If a colony of 10,000 bees in a nest site of 1 cubic foot breeds 1000 varroa per year, a colony of 20,000 bees with a nest site of 2 cubic feet would breed 4000 varroa per year.
Similarly a colony of 30,000 bees in a nest site of 3 cubic feet would breed 9000 varroa per year.

  This is due to large colonies breeding more drones allowing a more rapid varroa build up.

(7).There is a limit to the number of varroa a given quantity of bees can groom. Where the depth of comb increases in proportion with the hive capacity, and the distances travelled by the mite to reach drone brood increases accordingly, the bees have a proportional increase in grooming opportunity, and this compensation is sufficient to ensure the survival of larger colonies.

The varroa drop count for the years 1998 & 1999 for colonies of bees housed in untreated 'Hollow Tree' hives follow, together with other self-explanatory information.

In April 2000 I applied for a patent for this type of hive and the patent specification is also included.

My results and observations are not important, but if other people, in other places, with other bees, obtain the same results and arrive at the same conclusions, then my patent may have some intrinsic value.  

hollowtreemap.gif (31942 bytes) Map of England and Wales (Grid Referenced) Location of Wild Honeybee Colonies
Click image to see full size.
The hive consists of sections, about 6 inches deep, stacked upon each other. Sections are added at the bottom as the size of the colony increases to maintain a 6 inch gap beneath the comb. 
Each section has an outside measurement of 14 inches. 
The thickness of the wood being between 1 & 2 inches. 
The entrances are 1 inch diameter holes drilled in the sections as required. 
The roof is a piece of board 16 inches square 1-2 inches thick positioned on top. 
At least two entrances are provided for ventilation purposes. 
The comb depth will reach 32 inches after 2 years.
In the third year no increase was observed.
The floor debris is observed each week.

Barely, barely, quite contrary,
That's how my varroa grow,
I keep my bess, in hollow trees,
All in a row.

An Explanation regarding the Survival of Wild Bee Colonies

Grooming and the uncapping of cells containing deformed embryo bees is sufficient to limit the varroa mite population in wild colonies and is most apparent when there are more mites than available nest sites.
At this time the mites become more active and more easily groomed and the reduction of brood allows the nurse bees more grooming opportunity.
Graphs of bee population and varroa nest site availability for the parent colony and swarm are shown below.

Peaks in the varroa drop count should coincide with the 'more mites than sites' situation which occur around 6/6, 8/8 and 10/10.
At this time the varroa drop will also include immature mites obtained from uncapped cells which contained deformed embryo bees caused by multiple mite infestation. 

Weekly Varroa Drop 1998
(Untreated 'HT' hives)

Copy of 'Hollow Tree' experiment sent to interested beekeepers contacted during survey

The Hollow Tree Hive

The object of the Hollow Tree Hive is to reproduce in a convenient and monitorable situation the wild bee habitat of a hollow tree or chimney. The main features are that the available space for natural comb should be substantially deeper than it is wide.
There should be a 6 inch gap maintained between the underside of the comb and the floor.
The entrances should always be well above the floor level.
The above requirements are to prevent varroa regaining access to the colony after they have fallen to the floor, for whatever reason.
By observing on a weekly basis the floor debris of varroa, dead bees,etc,a study of the relationship between varroa drop and swarming, brood rearing and the broodless period during winter, will be possible.
Grooming may be a reason why live and recently dead varroa are found in numbers at particular times of the year.The colour and condition of the mite is also of interest.
The hive consists of sections about 6 inches deep stacked upon each other (Fig 2),sections being added at the bottom as the size of the colony increases. Each section has an outside measurement of 14 inches and the thickness of the wood between 1 and 2 inches.(Fig 1).
The entrances are 1 inch diameter holes drilled in the sections as required. The roof is a piece of board 16 inches square 1-2 inches thick positioned on top.
The bees glue it all together.
At least two entrances are provided for ventilation purposes.

Fig 1  - Fig 2

Fig 1                                                            Fig 2

The hive is then placed on an old 'National' floor. A piece of white formica 12 inches square is placed under the hive, covered with a thin coat of vaseline just sufficient to make the debris stick. To renew each week lift base of hive with hive tool at the front. Slide old formica square out and new one in. A wire loop fixed to the square is useful. No other interference is allowed, no smoke, no bayvarol, no honey, no end of interest. If the weekly varroa drop of dead mites exceed the MAFF requirement for treatment destroy colony. The experiment has failed. The graph underneath may be useful to plot weekly progress


Copy of Patent specification as applied for in the United Kingdom

Bee Hive

This invention relates to a Bee Hive

Bee hives in Great Britain have been infested with the varroa mite since 1992.
Unless treated, the bee colony dies due to this infestation.
Bees have an inherent ability to groom themselves free of the varroa mite.
In a conventional bee hive this is not apparent due to the hive entrance being at floor level which allows groomed varroa mites to regain the colony by attaching themselves to incoming bees.

A wild bee colony would construct a nest where the comb would be circular the size of a dinner plate, and a series of these would be constructed, as placed in a plate rack.

The honey stores would be in the top portion, the worker brood in the centre, with the drone brood underneath.

Varroa mites prefer to undertake their breeding cycle in drone brood when available.

The frames in the brood box of a conventional bee hive are much longer than they are deep which flattens the nest shape into an ellipse with the major axis being horizontal.

The honey store is now much closer to the drone brood and in consequence the necessary activity of the varroa mite during the breeding cycle is much reduced.

According to the present invention the Bee Hive is constructed to contain conventional size brood frames but rotated through 90° so that they are much deeper than they are wide which elongates the nest shape into an ellipse with the major axis being vertical. This increases the distances that have to be traversed by the varroa mite during its reproduction cycle which enhances the period of possible grooming which is sufficient to limit the varroa population allowing bees and varroa to live harmoniously together without treatment.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which-

Figure 1 shows the front and side elevation.

Figure 2 shows the cross section XX

Referring to the drawing the Bee Hive comprises of a Roof 1 and a Hive Body 2 which stands on a Floor 3.

The Hive Body contains six conventional bee hive brood frames 4 rotated through 90° and mounted in parallel.

The hive Entrance is positioned at 5 and the Space 6 is provided above Floor 3.

Wild colony in hedge

Side View

Front View

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