The Lives of Bees

by Thomas D Seeley

  (Fig. 2.14), it has left behind not only a busted- up bait hive lying on the

  ground but also a bunch of conspicuous calling cards: claw marks in the

  bark of the tree in which I had mounted the bait hive (Fig. 10.9, bottom).

  Because I have never found claw marks in the bark of the 17 other bee trees

  that I keep monitoring, I am convinced that the bears have never discov-

  ered the colonies in these trees. Why haven’t they? My reference book on

  the mammals of the eastern United States tells me that black bears have

  acute senses of smell and hearing but “only adequate vision.” Adequate for

  some things, but evidently not for spotting small bees coming and going

  from dark knotholes and slender cracks high up in trees.

  LIVING WITH VS. WITHOUT A PROPOLIS ENVELOPE

  We have seen already in chapter 5 that wild honey bee colonies living in

  tree cavities collect antimicrobial plant resins and use them to coat the

  ceilings, walls, and floors of their nest cavities, to create propolis envelopes

  around their nests. It is, therefore, quite telling that honey bee colonies do

  not form thick coatings of propolis on the inner surfaces of manufactured

  hives, though they will fill with propolis the crevices between the frames

  as well as any cracks around a hive’s lid. Evidently, the stimuli that elicit

  propolis deposition are small cracks and crevices (see Fig. 5.4). Surfaces

  that are rough and porous are ideal for bacterial growth, for they give

  bacteria abundant substrates to cling to as well as a supply of nutrients and

  moisture. And if left alone, bacteria living in these places will build bio-

  films that can protect them from being dislodged. It is not at all surprising,

  therefore, that honey bees work hard to coat the rough and porous surfaces

  of their nest cavities with plant resins.

  Many laboratory- based studies have tested the effectiveness of propolis

  against the growth of the causative agents of two brood diseases of honey

  bees: American foulbrood (a bacterial disease caused by Paenibacillus larvae)

  and chalkbrood (a fungal disease caused by Ascosphaera apis). All these stud-

  ies report strong inhibitory effects of propolis on these pathogens. It is not

  Seeley.indb 273

  2/21/2019 8:08:02 AM

  274 Chapter 10

  entirely clear, however, how the findings from these in vitro studies con-

  ducted in laboratories relate to disease control in colonies, especially be-

  cause it is not clear that honey bees consume propolis and incorporate its

  compounds in the food they feed to their brood.

  Marla Spivak and her colleagues at the University of Minnesota have

  assessed the health benefits to honey bees of living in a nest that is sur-

  rounded by a propolis envelope by listening to the bees themselves. One

  of their experiments involved comparing the transcription levels of

  immune- related genes in worker bees living in two types of hives. The

  hives in the experimental group had their inside surfaces coated with etha-

  nol extracts of propolis, while those in the control group had their inside

  surfaces coated with straight ethanol. After seven days, individual bees

  living in the propolis- enriched hives, relative to bees in the control hives,

  showed lower bacterial loads and lower levels of activity of genes involved

  in insect immune responses. Evidently, coating the insides of hives with

  propolis extracts lowered the levels of the immune elicitors (i.e., the lev-

  els of bacteria and fungi) in the treatment hives, relative to the control

  hives.

  Another experiment performed by the Minnesota group shows even

  more strongly the benefits of a propolis envelope to the health of a honey

  bee colony. This time, the researchers compared colonies with and without

  true propolis envelopes, and they ran their study for two years. Each year

  they measured multiple indicators of health in 24 colonies, 12 with and 12

  without propolis envelopes. They stimulated half the colonies to construct

  propolis envelopes by fixing sheets of plastic “propolis trap” material to the

  smooth inner walls of their hives, and the bees responded by coating these

  plastic sheets with propolis (Fig. 10.10). They left the inner walls of the

  hives of the other 12 colonies bare, and these colonies did not construct

  propolis envelopes.

  The experiment yielded two main findings. First, during the summer

  and autumn months, the expression (activity) levels of several genes in-

  volved in insect immunity were consistently lower and steadier in the

  worker bees living in hives with a propolis envelope, compared to workers

  Seeley.indb 274

  2/21/2019 8:08:02 AM

  Colony Defense 275

  Fig. 10.10. View of propolis deposited on the inner walls of a hive after the re-

  moval (at end of experiment) of the sheets of plastic propolis- trap material that

  investigators had stapled to the walls inside the hive. Left behind are the blobs of

  brown propolis that filled the slots in the propolis- trap sheets.

  in hives without a propolis envelope. This difference in level of immune

  gene expression is functionally significant, because when a bee’s immune

  system is working hard to fight infections, it can be the costliest part of

  her physiology. Lowering immune system activity, therefore, enables bees

  to allocate more energy to other tasks, such as brood rearing, wax produc-

  tion/comb building, and foraging. The second main finding is even more

  telling: colonies with propolis envelopes had better survival in one of the

  two years (Fig. 10.11), more brood in May in both years, and better nutri-

  tional status of its young workers in both years. The nutritional status of the

  young worker bees was assessed by measuring their levels of activity of the

  gene Vg. This is the gene that young worker bees activate to produce vitel-

  logenin, their primary storage protein. Indeed, in healthy young nurse

  bees, vitellogenin constitutes approximately 40 percent of the protein in

  their body fluids, for it is what these bees draw upon to produce protein-

  Seeley.indb 275

  2/21/2019 8:08:02 AM

  276 Chapter 10

  100

  75

  50

  25

  e

  April 2012

  May 2013

  100

  % colonies aliv

  75

  with propolis envelope

  50

  without propolis envelope

  25

  100

  200

  300

  400

  April 2013

  May 2014

  Time (days)

  Fig. 10.11. Survivorship records of colonies with a propolis envelope ( blue line)

  and without a propolis envelope ( magenta line), in two trials of the experiment.

  In each trial, there were 12 colonies in each treatment group. There was a signifi-

  cant difference in colony survivorship at the end of the first trial but not the

  second trial.

  rich royal jelly for feeding young larvae. Healthy, well- nourished nurse

  bees are the foundation of a colony’s brood production and growth, so

  what this ingenious experiment has revealed is that when a colony builds


  itself a propolis envelope, it is making a far- reaching investment in its fu-

  ture growth and ultimate success.

  Seeley.indb 276

  2/21/2019 8:08:02 AM

  11

  DARWINIAN BEEKEEPING

  Beekeeping today is still as it has always been: the exploitation

  of colonies of a wild insect; the best beekeeping is the

  ability to exploit them and at the same time to interfere

  as little as possible with their natural propensities.

  —Leslie Bailey, Honey Bee Pathology, 1981

  In the first 10 chapters of this book we have reviewed the interwoven top-

  ics of annual cycle, colony reproduction, nest building, food collection,

  thermoregulation, and colony defense that form the natural history of the

  honey bee, Apis mellifera. We have also examined the cultural history of

  beekeeping and the ways in which this unique form of animal husbandry

  is built upon, but also disrupts, the natural lives of these marvelous insects.

  This final chapter aims to integrate these two general themes, by applying

  what we have learned in recent decades about how honey bees live in the

  wild, to revise some of our beekeeping practices in ways that are mutually

  beneficial for bees and beekeepers. Our goal is to respect the natural lives

  of honey bees but also to enjoy the benefits of their hard work as honey

  makers and crop pollinators. We will work toward this goal in two stages.

  First, we will review the most important differences in living conditions

  between wild colonies and managed colonies, an exercise that will high-

  light the many ways in which standard beekeeping practices alter the lives

  of honey bees and often put these insects under stress. Second, we will

  look at ways in which beekeepers can revise their practices to make the

  Seeley.indb 277

  2/21/2019 8:08:02 AM

  278 Chapter 11

  lives of their six- legged partners less stressful and therefore more health-

  ful. We will see that the essence of doing this is to manage colonies of

  honey bees in ways that enable them to live, as much as possible, under

  conditions like those in which they evolved and thus to which they are

  adapted. We will also see that this often requires putting the needs of the

  bees before those of the beekeeper.

  WILD COLONIES VS. MANAGED COLONIES

  Again and again, throughout this book, we have seen that there are stark

  differences between the original environment that shaped the biology of

  wild honey bee colonies—their environment of evolutionary adaptation

  (EEA)—and the current living conditions of managed colonies. Wild and

  managed colonies live under different conditions because beekeepers, like

  all farmers, modify the environments of their livestock in order to boost

  their productivity. Unfortunately, these changes in the living conditions of

  agricultural animals often make them more prone to parasites and patho-

  gens. Table 11.1 lists 21 differences between the living conditions in which

  wild colonies have lived (and often still live) and the living conditions in

  which managed colonies of honey bees now live.

  Difference 1: Colonies are genetically adapted vs. are not genetically adapted

  to location.

  The process of adaptation by natural selection produced the differences

  in worker- bee color, morphology, and behavior that distinguish the 30

  subspecies of Apis mellifera that live within the species’ original range of

  Europe, western Asia, and Africa. The colonies in each subspecies are well

  adapted to the climate, seasons, flora, predators, and diseases in their na-

  tive region of the world. Moreover, within the geographic range of each

  subspecies, natural selection has produced ecotypes—populations that are

  fine- tuned to their local conditions. Perhaps the best- documented exam-

  ple of this geographical adaptation is the ecotype of A. m. mellifera (the dark

  European honey bee) that is adapted for living in the Landes region of

  southwestern France. The rhythm of its annual cycle of colony growth is

  Seeley.indb 278

  2/21/2019 8:08:02 AM

  Darwinian Beekeeping 279

  Table 11.1. Comparison of the environments in which honey bee colonies have lived as wild

  colonies and those in which they live currently as managed colonies

  Environment of evolutionary adaptation

  Current circumstances

  1. Colonies are genetically adapted to their

  Colonies are not genetically adapted to their

  location

  location

  2. Colonies live widely spaced in the landscape

  Colonies live crowded in apiaries

  3. Colonies occupy small nest cavities

  Colonies occupy large hives

  4. Nest cavity walls have a propolis coating

  Hive walls have no propolis coating

  5. Nest cavity walls are thick

  Hive walls are thin

  6. Nest entrance is high and small

  Nest entrance is low and large

  7. Nest has 10%– 25% drone comb

  Nest has little (< 5%) drone comb

  8. Nest organization is stable

  Nest organization is often altered

  9. Nest- site relocations are rare

  Hive relocations can be frequent

  10. Colonies are rarely disturbed

  Colonies are frequently disturbed

  11. Colonies deal with familiar diseases

  Colonies deal with novel diseases

  12. Colonies have diverse pollen sources

  Colonies have homogeneous pollen sources

  13. Colonies have natural diets

  Colonies sometimes have artificial diets

  14. Colonies are not exposed to novel toxins

  Colonies exposed to insecticides and fungicides

  15. Colonies are not treated for diseases

  Colonies are treated for diseases

  16. Honey not taken, pollen not harvested

  Honey taken, pollen sometimes harvested

  17. Combs not moved between colonies

  Combs often moved between colonies

  18. Honey cappings are recycled by bees

  Honey cappings are harvested by beekeepers

  19. Bees choose larvae for queen rearing

  Beekeepers choose larvae for queen rearing

  20. Drones compete fiercely for mating

  Queen breeder may select drones for mating

  21. Drone brood not removed for mite control

  Drone brood sometimes removed and frozen

  attuned to the massive bloom of ling heather ( Calluna vulgaris) in August

  and September. Colonies of honey bees that are native to this region have

  an unusual, second strong peak of brood rearing in August. This gives them

  a second burst of colony population growth that helps them exploit this

  late summer heather bloom. Colony transplant experiments have been

  performed in which colonies from the region around Paris (which lacks a

  heather bloom) and from the Landes region were moved to each other’s

  location and then their brood- rearing patterns were recorded. These ex-

  periments show that the difference in annual brood cycle between these

  Seeley.indb 279

  2/21/2019 8:08:02 AM

  280 Chapter 11

  two ecotypes has a genetic basis. This example shows us that shipping

  mated queens, and trucking whole
colonies, to places hundreds or thou-

  sands of miles away—for instance, from Hawaii to Maine or Italy to Swe-

  den—is likely to force colonies to live in environments to which they are

  ill suited.

  Difference 2: Colonies live widely spaced in the landscape vs. crowded in

  apiaries.

  This shift makes beekeeping practical, but it also creates a fundamental

  change in the ecology of honey bees. Crowded colonies experience greater

  competition for forage, greater risks of being robbed, and greater prob-

  lems in reproduction: swarms combining when leaving their hives, and

  queens entering the wrong hive when returning from their mating flights.

  Probably the most harmful consequence of crowding colonies, though, is

  boosting pathogen and parasite transmission between colonies. This facili-

  tation of disease transmission boosts the incidence of disease among colo-

  nies and favors the virulent strains of the bees’ pathogens and parasites.

  Difference 3: Colonies occupy small nest cavities vs. large hives.

  This modification also profoundly changes the ecology of honey bees.

  Colonies in large hives have the space to store huge honey crops, but they

  also swarm less often because they are not as space- limited. This weakens

  natural selection for strong, healthy colonies, since fewer colonies repro-

  duce. A more immediate problem of keeping colonies in large hives is that

  colonies suffer greater problems with brood parasites, such as Varroa, be-

  cause large, non- swarming colonies provide these parasites with a vast and

  steady population of their hosts: the larvae and pupae of honey bees.

  Difference 4: Colonies live with vs. without a nest envelope of antimicrobial

  plant resins.

  Living without a propolis envelope increases the physiological costs of

  colony defense against pathogens. It is now known, for example, that

  workers in colonies without a propolis envelope invest more in costly

  immune- system activity—such as synthesis of antimicrobial peptides—

  relative to workers in colonies with a propolis envelope.

  Seeley.indb 280

  2/21/2019 8:08:02 AM

  Darwinian Beekeeping 281

  Difference 5: Colonies have thick vs. thin nest- cavity walls.

  This amounts to a difference in nest insulation, which strongly affects

  the energetic cost of colony thermoregulation. This effect is especially

  strong when the colony is rearing brood and so is heating or cooling the