The Economy of the Hive – Part 1
Inside the hive there functions a vibrant community, with an economy similar to that of any other society. The bee economy is based upon the harvesting and processing of resources, the trade of products, doting care for the youngsters and parents, wise savings, deficit spending, a hierarchy of jobs, national defense, and an exquisite communication that allows democratic decision making.
We have an innate desire, or might I say, a demand, to determine the culprit responsible for dying colonies. However, it may well be that the “mystery” of colony collapses is akin to similar previous events such as Disappearing Disease (so named not because the bees disappear, but because the disease disappears after wrecking havoc for a year or two). Note that previous events occurred prior to the arrival of varroa, or even before the widespread use of synthetic pesticides.
I started this article with the thought of explaining in simple terms the mechanisms that lead to a “sudden” collapse which leaves only an empty hive containing a residual mere handful of young bees and the queen, since many beekeepers seem to think that this is an unusual phenomenon, requiring us to identify some novel villain. In reality, this symptom has been reported for as long as records exist, and is actually a common outcome of infection by any pathogen that severely shortens the life of adult bees—such as Nosema apis or some viruses.
As my readers may have noticed, my curiosity gives me no respite, and I found that in order to understand the mechanics that cause a colony to collapse, that I needed to delve deeply into bee behavior, pheromones, nutritional economics, parasites, and immune responses. I find in general, that the more thorough an effort I make to understand the biology of the bee, the less mysterious the phenomena that I observe in the field become, and the better practical management decisions I can make. At the same time, the more that I learn about this “super-organism” that we call a colony of bees, the more amazed I am by the complex dynamics that go on within the hive! (I suggest that every beekeeper read Jürgen Tautz’s wonderful 2008 book, subtitled “Biology of a Superorganism).
To truly grasp how a colony “thinks,” one must understand the economy of the hive. The bee economy is similar to that of our own in the USA—which is based upon a plentiful supply of food, yet must contend with having its wealth drained off by parasites (Wall Street and credit card companies come to mind), being hammered by drought and storm, war on multiple fronts, and the current skirting of economic collapse. And just as does our own, the bee colony rallies to respond to those challenges—sometimes it is successful, sometimes not.
This article kicks off a series that will begin with a description of the hive economy, to be followed by articles on colony communication and the modeling of its behavior—that is, how a colony “thinks” and adjusts to changing environmental conditions. Then we will deal with parasites, disease and the colony immune response, and then colony collapse. Finally, I hope to make suggestions as to directions that we can take in the breeding of bees for a robust future of beekeeping.
I realize that this is an ambitious undertaking, especially since I am forced to do much of my research and writing while on the road, or pounding on the sticky keyboard after days in the bee yards and honey house. However, these are rough times for beekeepers, and I’m encouraged by the appreciation that I receive for my efforts. I’m heartened by the desire by many to become better beekeepers, and by their hunger for knowledge about this fascinating insect society that so captivates us.
I’d like to make clear that I am no Cassandra predicting the demise of the bee (although beekeepers are certainly having a tough time). It’s clear that bees are facing serious challenges from the varroa mite and our associated miticides, viruses, and Nosema ceranae, along with climate change, and the “clean farming” of pesticide-laden vast monocultures. But bees have always demonstrated an amazing resiliency, which I fully expect to play out again.
Neither will I proselytize that beekeepers need to do this or that. Bees don’t ask for much—a dry box and plenty of flowers. But they do benefit from common sense good husbandry. The more that the beekeeper understands about the economy of the hive, the better he or she can make wise management decisions.
So let’s begin with…
The Fertilized Egg—two potential paths
In this article, I’m going to restrict the discussion mainly to the females of the colony, since the presence of drones is not necessary for day-to-day colony function. The default for any fertilized egg is to develop into a queen (except in the rare case of diploid drones, which are immediately eaten). Now that statement may come as a surprise to some, but think of it this way: the ancestral female solitary bees were by necessity all “queens”—each performing all functions necessary for a simple life cycle. The queen is actually the “generic” form of bee, since she is similar to the ancestral solitary bee.
In reality, it is the workers who are the “special” bees in the colony, and it is the queen who serves them, by providing eggs when she is given the signal, and the pheromones necessary for colony cohesiveness. In order to form a larger bee society, a versatile “worker” caste was created—the members of which are able to perform all the various functions required in bee society at some stage of their lives, other than that of laying eggs (and in actuality, workers are even able to do that under the right circumstances).
Worker bees are created from potential queen eggs essentially by withholding food, which in turn tweaks the epigenetic expression of their genes, so as to form a very different multipurpose body with specialized structures—larger antennae and eyes, wax glands, special mandibles, pollen rakes, press, and basket, and a barbed sting. (I’ll be covering epigenetics at length in an upcoming article).
The development of the worker caste allowed the bee to “grow” in size from that of a single insect into the fifteen- to twenty-pound mammal-like, warm-blooded, super-organism that we call a “colony” of bees. This larger organism was then able to move out of the tropics, and by utilizing tree hollows as homes, has been extremely successful at colonizing the forage-rich temperate regions of Earth.
We can better understand the dynamics of colony sociality by looking at how it evolved from the bees’ solitary ancestors. A typical life cycle began after a long resting phase (as an adult or pupa), then progressed to a foraging/provisioning phase (when food was available) during which the solitary female built and stocked her nest with pollen, which then stimulated the development of her ovaries. She then laid an egg, sealed (and eventually abandoned) the nest, and then repeated the foraging phase again and again until she died (Hunt 2007).
Note that the honey bee colony follows similar phases—a long “rest” when there is no pollen available (during winter in temperate climes), then a frenzied provisioning phase through the spring/summer pollen flow, during which the colony builds up stores of protein in the form of a large body of workers, and creates reproductive forms (drones and swarms). The beauty of the honey bee colony is that it does not die after reproduction (as do bumble bee colonies), but can continue to store enough food to survive over the winter, thus giving it the ability to reproduce again the next season (and to get a jump start on the early spring bloom). The honey bee colony is thus essentially immortal—unless it is killed by a predator, lack of food, or disease, it can live forever, reproducing in most years.
No solitary insect could possibly do this, since adult insects cannot regenerate their worn external appendages, such as wings or legs. But the colony of bees, in which each bee functions analogously to a single “cell” of a larger super-organism, can regenerate its individual cells (even a failing reproductive queen, by the process of supersedure).
The key to the transition from a solitary “queen” performing all the work, to a fully functioning immortal colony, was the development of “alloparental” (other parent) nursing of developing younger sisters by the queen’s previous daughters. This led to the development of a “worker” caste of bees—potential queens that by virtue of being raised in smaller cells and on a less nutritious diet, never fully develop their reproductive stature, and remain nominally sterile.
The outcome of this sociality is the fascinating division of labor in the colony by workers as they progress through a series of jobs, dependent upon their developmental “age” and the needs of the colony. Our understanding of the molecular basis of this “age polyethism” (age-dependent changes in behavior) has been greatly expanded by recent research by Drs. Stig Omholt, Gro Amdam, Robert Page, and their coworkers (see References).
One might ask why Joe Beekeeper should care about the molecular basis of polyethism. The answer is that it involves nutrition, pheromones, immune function, and the aging of bees—the understanding of which allows us to grasp how the colony “thinks and decides,” why it thrives or gets sick, and how we can better practice good bee husbandry.
For our purposes, let us return to the ancestral model. The main jobs that bees need to do are to forage for food (forager bees), then process that collected food and to convert it into new bees (the job of nurse bees), and to be able to become long-lived “resting” bees that can survive food dearths for extended periods. Of course, there are also a number of other jobs performed (largely by “middle aged” bees), such nectar storage, comb building, cell cleaning, guarding, etc., but those jobs are secondary to the major three.
Nurse bees are the protein gatekeepers for the colony. They are specialized to digest pollen, and to convert it into protein-rich jelly, which they then use to feed the three ravenous mouths of the colony—the queen, the brood, and the protein-hungry returning foragers. None of those three groups digest pollen to any extent themselves—they are totally dependent upon the jelly produced by the nurse bees. The jelly can be thought of as the “currency” of protein in the colony (we will return to this later).
Nurse bees are like mother mammals—they are voraciously hungry, and store food reserves in their bodies in order produce sustenance for their young. They live in a sheltered, safe environment, and enjoy an expected long life. They therefore invest in a ramped up immune system, anti-aging free radical scavenging, and cellular repair (please refer to my “Fat Bee” and “Old Bee” articles for details). Their strong investment in immune function is important, as they must produce parasite-free food for the queen and larvae.
Practical Tip: Well-fed nurse bees will keep the young larvae “swimmin’ in jelly.” Lack of “wet” brood is a sign that the colony is short on protein, and might benefit from being given a pollen supplement.
Forager bees face a dangerous environment outside the protection of the hive. Their lives are defined by the risks of predation, poisoning, chilling, wind and rain, and the wearing out of their wings. They are considered by the colony to be expendable, and therefore do not devote much energy into immune function or cellular repair. Weather and forage permitting, they simply work themselves to death in a matter of days.
Practical Tip: Anything the decreases the life of the fragile foragers can keep the colony from building up a large population. Such impairments include mites, nosema, viruses, pesticides, and poor nutrition. Check any “lagging” colony for the cause!
The ancestral honey bees from Africa were likely adapted to food dearths between rain events. They could shut down brood rearing and wait out the drought until rains again brought food, living in the interim off their stores of honey and beebread (or in the case of savannah bees, absconding to go looking for fresh forage). This preadaptation served them well when they invaded the European temperate climate, since they already possessed mechanisms for conserving their energy and stores, and to extend their lives as “resting” bees (Amdam 2005).
“Resting” bees are commonly referred to as “winter” bees. However, Mauritzio (1954) found that one could induce the formation of “winter” bees even during the summer by restricting the queen from producing brood. This adaptive shift to extended longevity is a response to the cessation of pollen income into the colony (Mattila and Otis 2007 ), which “tells” the younger bees in the colony to conserve protein and hunker down for a while. Very unlike the short-lived foragers, they can then live for a considerable period of months. Indeed, Peter Borst points out that in northern climes, a colony of bees spends a larger portion of the year as resting winter bees than they do as nurses or foragers!
This “suspended animation” mechanism is a critical component for colony survival during times of pollen dearth. The technical term for these resting bees is “diutinus” bees. By loading up their bodies with storage proteins, they can then form a resting cluster that does not have to process pollen nor leave to defecate. Diutinus bees carefully ration their protein reserves, using them at a fraction of the rate that other workers do. They also invest in immune and detoxification functions, since they must prevent disease from spreading in the resting cluster.
Practical Tip: One should avoid disturbing the winter cluster. Stimulative syrup feeding or the occurrence of unseasonable warm weather without pollen or supplement available can result in “fruitless foraging” that wears out the winter bees.
Nurse bees that haven’t raised too much brood can transform into diutinus bees, as can foragers who haven’t worn themselves out (they are able to renew their youthful immune function). When conditions get better, diutinus bees can then again transform into either nurse bees or foragers.
Practical Tip: Any time that a colony goes into the resting state, there will be no brood for varroa to hide in. This is a good opportunity to use oxalic acid dribble, or in warm weather, sugar dusting to kill varroa mites.
Colony nutrition, and the importance of royal jelly in the economy of the hive.
As always, I am deeply indebted to my collaborator in research, Peter Loring Borst. I also appreciate the generosity of Drs. Zachary Huang, Rob Page, Gro Amdam, Heather Mattila, and Tom Seeley, who took the time to answer my questions and share unpublished research.
Amdam, GV and SW Omholt (2002) The Regulatory Anatomy of Honeybee Lifespan. J. Theor. Biol. 216: 209–228.
Amdam, GV, et al (2004) Hormonal control of the yolk precursor vitellogenin regulates immune function and longevity in honeybees. Experimental Gerontology 39 (2004) 767–773.
Amdam, GV, et al (2005) Higher vitellogenin concentrations in honey bee workers may be an adaptation to life in temperate climates. Insect. Soc. 52: 316–319.
Amdam, GV, O Rueppell , MK Fondrk, RE Page, CM Nelson (2009) The nurse’s load: Early-life exposure to brood-rearing affects behavior and lifespan in honey bees (Apis mellifera). Experimental Gerontology 44: 467–471.
Hunt, J (2007) The Evolution of Social Wasps. Oxford Univ. Press.
Li, Z, et al (2009) Vitellogenin is a cidal factor capable of killing bacteria via interaction with lipopolysaccharide and lipoteichoic acid. Molecular Immunology 46: 3232–3239.
Mattila HR and GW Otis (2007) Dwindling pollen resources trigger the transition to broodless populations of long-lived honeybees each autumn ECOLOGICAL ENTOMOLOGY 32 (5): 496-505.
Maurizio , A (1950) The inﬂuence of pollen feeding and brood rearing on the length of life and physiological condition of the honeybee: preliminary report. Bee World 31: 9–12.
Nelson CM, Ihle KE, Fondrk MK, Page RE Jr, Amdam GV (2007) The Gene vitellogenin Has Multiple Coordinating Effects on Social Organization . PLoS Biol 5(3): e62.
Otis, GW, DE Wheeler, N Buck, HR Mattila (2004) Storage proteins in winter honey bees. Apiacata 38: 352-357.
Schmickl, K & K Crailsheim (2004) Inner nest homeostasis in a changing environment with special emphasis on honey bee brood nursing and pollen supply. Apidologie 35: 249–263 This is a “must read” article for the serious beekeeper, which can be downloaded free at http://www.apidologie.org
Seeley, T.D. (1995) The Wisdom of the Hive. Harvard Univ. Press
Tautz, J (2008) The Buzz about Bees: Biology of a Superorganism. Springer.
Webster, T and Y-S Peng (2002) The evolution of food-producing glands in eusocial bees (Apoidea, Hymenoptera). Journal of Evolutionary Biology 1(2): 165-176.