2 The Superorganism and Herd Health for the Honey Bee

       Robin W. Radcliffe

       Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA

       * Illustrations by Anna Connington

Introduction

      The honey bee colony is a magnificent product of evolution. Collective decision‐making of thousands of individual bees, each with roles that change as they age, work seamlessly together to create a highly integrated system (the colony) that functions as a single organism (the superorganism). In this chapter we will explore the marvelous world of the honey bee with a focus on how the organization and structure of the colony allows honey bee societies to function as a single coordinated living entity. The superorganism must build new comb, make replacement bees, collect food, water, and hive materials all while protecting their home from pests and pathogens, and survive to reproduce by casting a swarm and sending off drones. Deviations in any one of these collective pathways can lead to disorders, disease, or colony failure.

      We will follow the honey bee as it allocates tasks in sophisticated communication networks that help prevent the spread of pathogens, make and use organic compounds to fight disease, collect plant resins to make propolis, and manipulate the hive environment to prevent and even treat infections in the colony. In an extraordinary example of social behavior, we will also learn how honey bees can treat themselves and prevent disease by working as their own “doctors”! These novel methods of disease control and mitigation are just now becoming well understood. The marvels of resin and pollen collection and the myriad bioactive elements in these compounds, collected from nature itself, offers wonderful insights into the ways that honey bees protect themselves from harm. The health benefits of propolis to human health have been known since the days of the ancient Greeks, Romans, and Egyptians; the word itself comes from the Greek “pro” to defend and “opolis” the city, or in this case the beehive or wild nest. Here we will explore the value of propolis to the bees themselves, a topic deserving of more in‐depth research. Honey bees can also control fundamental environmental conditions that are protective against disease, including the remarkable ability to regulate the “body temperature” of the superorganism. Used against large invaders such as a bumble bee that attempts to enter the colony, honey bees use heat to “bake” the invader in a ball of heater bees, while small invaders such as some bacteria and fungi that infect the brood are killed by small elevations in temperature (enough to kill the pathogen, but not the developing brood). Scientists call the latter a “social fever”, and it is another example of how the colony can ward off infections through cooperative action.

      Finally, the health and fitness of honey bees as a superorganism can be examined and evaluated in much the same way as a herd of livestock – herd health for honey bees offers a big picture “lens” through which serial monitoring of population level determinants of health are made. An understanding of how honey bees coordinate important hive processes (including collection of pollen, nectar and tree resins, coordination of bee caste populations, maintenance of biosecurity, and ensuring a healthy living environment) combined with the collection of relevant data will provide one of the most important tools for the bee doctor to help decipher health at the level of the colony working in concert with the beekeeper.

Part 1: The Superorganism and Swarm Intelligence

      At the peak of summer activity, an estimated 30 000–50 000 bees live in close proximity within the confines of the typical beehive, or a bee tree if a wild colony. The value of social living must exceed the disadvantages of being closely packed together since parasites and pathogens can exploit the high density of individuals and their