Honeybee Biology

 

The Capensis problem

The honeybee colony has an intricate social structure where different casts play vital roles in its survival and procreation. This is further complicated by task definitions of workers to provide forage and water; tend the brood, queen and drones; defend the colony; maintain optimal humidity and temperature levels in the nest; and building combs. Studying the biology of the honeybee and social structure of the colony is crucial in optimizing the potential and worth it has in and for agriculture and in developing new and better beekeeping methods.

The unique characteristic of the laying workers of the Cape honeybee (Apis mellifera capensis) to produce females from unfertilized eggs was first described in 1912. Initially this characteristic known as thelytokous parthenogenesis was regarded as peculiar and scientifically interesting but not of any real importance. This changed between 1977 to 1979 when some experimental colonies taken from the Cape peninsula were placed in an African honeybee, (Apis mellifera scutellata) apiary in the summer rainfall region. This resulted in many African honeybee colonies being taken-over by laying workers of the Cape honeybee which soon died out. A catastrophe was averted when all the infested colonies in that apiary and in a radius of 3.5 km were killed to prevent the problem from spreading to other beekeepers.

Beekeepers, through subsequent warnings, for many years thereafter refrained from mixing the two sub-species. However, in 1991 capensis laying workers were identified in honeybee colonies of commercial beekeepers in the summer rainfall region. As the problem escalated, thousands of colonies died out. In an effort to prevent the total destruction of all hived colonies in the region, the South African government issued a proclamation that all infested colonies should be killed. Compensation was paid to those commercial beekeepers who could prove that they had complied with the law. Despite these strict measures the problem persisted, and it is still the most serious one plaguing beekeeping outside the geographical distribution area of the Cape honeybee.

Contact: For general information on Apis mellifera capensis
Mr. Mike Allsopp
E-Mail: allsoppm@arc.agric.za
Center: Vredenburg, Stellenbosh

Recommendations for beekeepers regarding the Capensis problem

The only way to prevent Cape problem bees from killing colonies is to eliminate the problem before it starts.

• Trapped swarms should be tested by beekeepers to confirm their purity. Only those that prove beyond doubt to be pure scutellata must be used for beekeeping.

• Beekeepers should not place their colonies in the same areas as beekeepers that may have the Cape problem bees in their colonies.

• Basic hygienic procedures should be followed when working with bees. The more colonies that are worked during a single day, the higher the chance of transferal of Cape problem bees between colonies.

• Reduce movement of bees and brood frames between apiaries to the minimum. It has been demonstrated that not only can apiaries be kept capensis free, but also even if part of the population has been taken over, the problem can be contained to a single apiary.

• Select colonies and start a breeding program by rearing queens and drones from the selected colonies. The breeding station should be as isolated and as free of wild swarms as possible to prevent 'unwanted' genetic material entering the breeding lines.

• General good management practices such as keeping good records of queen replacement and colony performance will go a long way to curtail and eventually eliminate the problem.

Thelytokous partehenogenesis 

Under natural conditions the queen mates once with drones and stores their sperm in her spermatheca for as long as she lives. She regulates fertilsation of the eggs as they pass from her ovarioles past her spermatheca. Those laid in worker cells are fertilized (2n) while those laid in drone cells are not (n). If a queen is removed from, or lost to a colony, some workers will develop into laying workers. Because they were never mated they can not fertilize their eggs and therefore lay only haploid (n) eggs that develop into drones. However the Cape honeybee is unique in this regard because when laying workers develop they can produce worker offspring as a result of a process called telytokous parthenogenesis.

Thelytoky is the term used to describe the development of diploid (2n) eggs without fertilization, which in the case of honeybees can give rise to workers or queens (females). This is the opposite of arrhenotoky where haploid (n) eggs develop because no fertilization took place.

The outcome of thelytokous parthenogenesis is a new female genetically almost identical to the worker that produced the egg. Therefore, the offspring of capensis workers can be called pseudo-clones. Hence, once a Cape laying worker has successfully reproducing in an A. m. scutellata colony its offspring will have the same genes and are likely to be able to do exactly the same.

Eggs laid by workers of Apis mellifera capensis result from a normal meiosis followed by a fusion of one pronucleus with the central nucleus to regain diploidy. This process is called automixis.

It is uncertain why thelytoky has evolved in the A. m. capensis bee, but it is generally believed that the environment (strong winds) and/or forage (fynbos biome) are involved.

Research and results on the Cape problem bee

Soon after the report in 1996 that Capensis laying workers were widespread in African honeybee colonies the Director-General of the National Department of Agriculture appointed the so-called Capensis Working Group. This group was tasked to study and solve the "capensis problem". Chemical control could not be used against the capensis laying problem worker bees. Extensive research held the only reasonable hope of solving the problem.  

• Capensis surveys

• Disease and parasite surveys

• Pheromones

• Improved managements

• Social parasitism

Many beekeepers assisted in the programme at their own expense and contributions in kind were probably worth more than a million rand. What follows is a synopsis of the research and results of the Capensis Research Progamme.

Capensis surveys:

Comprehensive surveys were launched to determine the extent of the problem. The aims of the surveys were to map the distribution of the problem and determine over time the impact (colony loss) the laying workers caused. Twenty colonies per apiary of sedentary and migratory apiaries of small-scale as well as commercial beekeeping operations were surveyed. The colonies were visually inspected and worker bees were sampled three times (at 6 monthly intervals) over a one and a half-year period. The collected bees were dissected to determine ovariole numbers, spermatheca size and stage of egg development.

Results:

Capensis laying worker colonies were found throughout the summer rainfall region in sedentary as well as migratory colonies. Although the number of colonies that were taken over varied between apiaries, the severity of the problem didn't. Most colonies that were taken over died out within a year.

Disease and parasite surveys:

Inspecting a colony

To eliminate the possibility that colonies died of known diseases rather then capensis take-over a survey of diseases and parasites was done concurrently with the capensis survey. Hives were visually examined and brood and workers collected and analyzed for the following important diseases: European foulbrood, American foulbrood, Nosema, chalkbrood, Tracheal mites, Varroa, viruses including sacbrood, and malpighamoeba. Results: No disease was found that caused serious colony deaths or that exhibited the same symptoms seen in capensis infested colonies.

Pheromones:

To suppress the Capensis problem bees from taking over A. m. scutellata colonies chemical signals (pheromones) emitted by A. m. capensis queens to control capensis workers from becoming laying workers while the queen was still present was studied. Such compounds could be synthesized and introduced into colonies in affected regions to control the capensis problem.

Results:
No pheromones have yet been isolated but the search is continuing.

Improved management:

1. To test whether the distance between the queen (in the brood chamber) and the workers (in the top supers) had an effect on the development of capensis laying worker development, two sets of colonies were compared. In the one set two supers were added while four supers were added to the second set. These two sets were similarly managed in all other aspects for a one-year period.

   Results:
   The colonies with four supers were more likely to be taken over than those with only two supers. It will, therefore, be better to keep the colonies smaller and rather harvesting more often than stacking supers.

    

2. The effect of colony manipulations and/or stress placed on the queen and colony during migratory beekeeping in a commercial operation was tested. The percentage colony loss in two sets of colonies: one of which followed the standard migratory route of 5 moves, whereas the other followed a presumably less stressful route of 2 moves was compared.

   Results:
   Colonies moved more often were more like to be taken over. Wheather it was the stress placed on the colonies or the increased chances of drifting due to the increased manipulations and re-orientation of bees moved to new areas was not ascertained. Another interesting finding was that the beekeeper's profit margin was greater with fewer migrations.

Social parasitism: 

Not all infestations could be accounted for by drifting of workers between colonies or accidental introductions of workers or brood through normal colony manipulations. To determine whether the infestation was directed or non-directed, and whether residual remains of a queenless capensis-infested colony could give rise to a new capensis colony as a further source of infestation, was tested. These experiments were done in the natural capensis distribution area.

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