Byron N. Van Nest, PhD
The honey bee
I have been studying the European honey bee (Apis mellifera) for more than a decade. The honey bee is enormously important agriculturally and economically, and from a behavioral ecological point of view, it is just a fascinating animal. It is a cosmopolitan species (existing on every continent except Antarctica) and exhibits a wide repertoire of elaborate behaviors, ranging from cooperative brood care to complex problem solving. Honey bees possess a "continuously consulted circadian oscillator", allowing them to navigate by the position of the moving sun and to memorize not just the locations of multiple foraging sources, but also the times of peak productivity of these sources. And, famously, they can communicate source locations to their hive mates. In fact, the honey bees are the only animals outside of the mammals that are capable of using a symbolic language (the "waggle dance"). Honey bees can even count!
Honey bees are also famous for their unusually large brains. While there are other examples of large brains among the insects (e.g., cockroaches, some beetles, some butterflies), the honey bee brain is still much larger than most insect brains. It has has approximately 850,000 neurons in about one cubic millimeter of volume. One prominent structure within the insect brain is the so-called mushroom body (the input region or "calyx" of one mushroom body is shown here). These are paired structures, one per hemisphere, and are associated with sensory integration, learning, and memory. The mushroom bodies of the honey bee are also unusually large, with approximately 340,000 neurons total (accounting for approximately 40% of the whole brain). In comparison, the fruit fly (Drosophila melanogaster) only has about 130,000 total neurons, and only about 2,000 of those are in the mushroom bodies. Interestingly, this little fruit fly brain is actually fairly representative of most insect brains. The honey bee brain, then, really is a learning machine.
It is usually assumed that the enormous brains of honey bees allow for their elaborate behaviors, and this is almost certainly true. But we know that there is variation in both size and organization of the honey bee brain, and these vary by both age and life-long experience. It is usually further assumed that these differences endow some kind of benefit on the individuals that possess them, but this has never actually been tested. This is one of the areas of research that has consumed me for the last several years. Stay tuned for answers.