What a Bee Knows

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What a Bee Knows

What a Bee Knows

Exploring the Thoughts, Memories, and Personalities of Bees

Stephen Buchmann

© 2023 Stephen L. Buchmann

All rights reserved under International and Pan-American Copyright Conventions. No part of this book may be reproduced in any form or by any means without permission in writing from the publisher: Island Press, 2000 M Street, NW, Suite 480-B, Washington, DC 20036-3319.

Library of Congress Control Number 2022946104

All Island Press books are printed on environmentally responsible materials. Manufactured

Keywords: angiosperms, animal communication, animal intelligence, arthropods, bee, beehive, beeswax, bumblebees, cognition, consciousness, cuckoo bees, Charles Darwin, dreaming, emotions, eusocial, flowering plants, foraging, hearing, honey, honey bees, honeycomb, Hymenoptera, learning, magnetoreception, memory, mosaic vision, mutualism, navigation, nectar, neurons, pain, pollen, pollinators, self-awareness, sentience, sexual selection, sleep, smell, social bees, social brain, solitary bees, sun compass, superorganisms, taste, tool use, UV vision, vulture bees, waggle dance

Dedicated to my entomological mentors: Phillip A. Adams (CSUF), John Alcock (ASU), Earle Gorton Linsley (UCB), and Robbin W. Thorp (UCD)

Preface

The sight and sound of a bumblebee or a honey bee buzzing from flower to flower in an alpine meadow or a roadside planting is calming to many, yet it invokes outright panic in others. This happens frequently in Western cultures, where we usually reach for a spray can of insecticide or swat at any flying insect rather than pause to admire its beauty or reflect upon its captivating and intelligent behaviors. We delight in the viscous sweetness of honey on the palate, direct from the jar or slathered across a piece of toast. We savor the distinctive and flavorful honeys ripened from floral nectars but don’t care for confronting the winged honey makers. Do you remember the last time you took a break and watched the passing escapades of a brightly colored bee, wasp, or butterfly? In the West, entomophobia—trepidation and anxiety around insects—is well developed, perhaps as strong as our apparently inborn dread of venomous snakes. We’re convinced that every bee is hell-bent on stinging us and that a single sting will be lethal. Not surprisingly, these largely unwarranted fears and irrational phobias support a thriving global pest control industry based upon deadly yet nonspecific chemicals.

In the United States, there are at least 28,000 mostly sole-proprietorship pest control businesses employing more than 137,000 people, a rapidly growing industry valued at $17 billion annually.1 Over 1 billion pounds of insecticides are used in the United States each year. This is almost three times the amount of neuroactive chemicals (350 million pounds, including 63 million pounds of DDT) that were applied during 1962, the year Rachel Carson published Silent Spring, her revolutionary environmental science book.2 Apparently, we haven’t changed our actions or our ever-increasing chemical assaults against pollinating insects, and indirectly against ourselves, in the six decades since Carson’s prescient warning.

In my scientific travels, I’ve noticed strong cultural contrasts in people’s attitudes toward insects, especially toward aculeates, those

insects—such as ants, bees, and wasps—that bear a defensive stinger capable of delivering potent and painful venom. In many Asian cultures, there is more appreciation of bees and other insects in art, poetry, and everyday life than in the United States. In Japan and China, for more than a thousand years, various cricket species have been kept as pets in bamboo or molded gourd cages.3 These pets are revered for the repetitive chirps of their mate-calling songs. The Chinese also have a long tradition of gambling on the outcome of cricket fights. The insect gladiators are kept in special cages, cared for, and fed special, often secret, diets or allowed to engage in sexual congress before a bout. The latter is thought to enhance their fighting skills. In America, a cricket on the hearth is more likely to elicit a shoe thrown at the little songster.

I ask you to consider bees in a different way, perhaps for the very first time in your life. Come along with me on a global journey of discovery, shock, and awe into the minds and lives of bees. Give bees a chance. Discover them for yourself, examining their ways, their senses, how they learn, remember, think, and decide. Along the way, I hope your fight-or-flight reaction to a flying bee will change once you know bees a little better and that you may appreciate their engaging behaviors as much as I do.

Around the world live some twenty-one thousand distinctly different species of bees.4 They are typically solitary females digging their own nest tunnels in the ground or in dead wood without any help. Others are truly social, living among tens of thousands of their sisters and hive mates and their queen mother. Whether social or solitary, bees are individuals. They have distinct personalities. They learn and memorize important details of their world.

Bees also have a time sense and return to the same flowers at just the right time when the flowers are actively producing nectar. Most bees find their flowers, or other bee larvae as prey, by individual initiative. Others use chemical signposts or an elaborate “waggle dance” to recruit nestmates, informing them about the direction and distance to rewarding patches of flowers.

Most bees are gentle vegans, subsisting upon the pollen and nectar made by flowering plants. Certain “cuckoo bees” sneak their eggs into the open brood cells of unrelated bees. Upon hatching, their larvae stab and

kill the host bees’ eggs or young larvae with their ice tong–like jaws. A few kinds, the “vulture bees” from Panama and Brazil, make their living by locating vertebrate carrion, ingesting it, and turning those carcasses into a substance similar to royal jelly to feed their young.5

Where did this incredible diversity begin? About 130 million years ago, the world’s earliest known bee evolved from its wasp ancestors, which likely hunted tiny insects called thrips.6 One example of this earliest bee was found nicely preserved in golden amber, fossilized plant resin, from Myanmar (Burma). Flowering plants evolved a bit earlier, around 140 million years ago. These earliest angiosperms were likely first pollinated by flies and beetles. But with the evolution of bees and their transition to herbivory, bees started to nearly exclusively visit flowers for their food. By the Eocene epoch, some 56–34 million years ago, bees were mostly highly faithful and dependable visitors of the world’s flowering plants.

From this humble beginning, the long and important relationship between bees and flowers has developed. Usually, we consider them to be mutualists, with each one helping the other. Flowers are living billboards, displaying their beguiling scents and colors as advertisements for sexual favors. More than that, flowers are unabashedly plant genitals exposed on a stem for all to see. Your expensive florist’s bouquet should be X-rated. Stalked anthers house thousands of pollen grains, themselves containers for gametes, the male sex cells of flowering plants. Think of pollen as plant sperm cells. Centrally placed in most flowers is the style, with its sticky receptive end. This is where pollen grains land, sending their pollen tubes and gametes down into the heart of the flower to fuse and fertilize its ovules, like tiny peas inside their pod. The ovules become seeds within fruits. Although many plants can and do self-pollinate, thereby producing seeds, the best and most favorable genetic solution is for a distant and unrelated plant to father the seeds of a mother plant. This gives them the best chance of passing along their genes to healthy, fit offspring.

This is where bees and other vagile, or mobile, pollinators come into play. They can fly and plants cannot. They do the plants’ traveling for them. Think of bees as travel agents on scouting missions. About 85 percent of the world’s approximately 369,000 species of angiosperms

(flowering plants) rely upon animal pollinators, their sexual go-betweens.7 In temperate zone regions, bees pollinate about 80 percent of flowering plants. Rooted and immobile—except for leaf and stem movements or their fruits or seeds hitching a ride upon or inside birds, mammals, and even one type of seed-dispersing bee—plants don’t get around much. To go on a date, a flower must either be a prom corsage or enlist surrogate aid from the wings and legs of a passing bee. Tiny desert bees might fly only 50 meters (about 150 feet) from their nest to a flower. Other bees might travel vastly greater distances, 3.2–6.4 kilometers (2–4 miles) or even 14 kilometers (8.7 miles) in the case of a honey bee.8 Bees can move pollen over great distances.

Bees aren’t purposefully doing favors by moving flowering plant sex cells around. No, bees visit flowers for their own purely selfish reasons. Pollen and nectar are floral rewards that bring bees to flowers and hold their attention. Bees collect pollen and nectar as food for themselves and their immature brood, their blind, grublike larvae within carefully formed underground brood cells. Bees’ daily hunt for food is a life-anddeath matter. Depending on floral resources and the weather, a bee might pollinate as many as ten thousand flowers in a day.

Because of the branched hairs on their fuzzy bodies, the oily, sticky pollen grains, and often a little help from electrostatics, when bees brush against anthers, pollen sticks to them. Pollen grains also lodge in “safe sites” where bees can’t remove them—just as we can’t easily scratch between our shoulder blades. This tiny fraction of unreachable pollen grains that isn’t brought home and eaten by the bees makes possible the pollination of wild plants and crops alike. When bees move from flower to flower, they accidentally deposit viable pollen grains onto floral stigmas. Later, fertilization occurs, and seeds ripen inside fruits.

This is indeed a lucky accident for fruit- and seed-eating wild animals and for humans. We should thank bees and other pollinators for every third bite, about 35 percent, of the world’s food supply that isn’t derived from wind-pollinated cereal crops.9 Through the food gathering and pollination accidents of bees and other pollinators, the world’s most nutritious and tastiest fruits and vegetables are brought to the tables of the world’s 8 billion people. Indirectly, bees keep us well-fed. Rice, corn, and wheat are okay, but personally I prefer to eat the myriad

colorful and nutrient-dense plant foods brought to us on the wings of bees. Annually, the value of these pollination services, mostly due to bees, is $235–$577 billion globally and $6–$14 billion in the United States.10 We truly need to be thankful to bees for our bountiful harvests.

Bees prefer flowers that are blue or yellow and have sweet scents, which offer nectar containing 30–50 percent sugar.11 Think your child has a sweet tooth? Not compared with bees. Coca-Cola Classic is only 10 percent sugar and 90 percent water. Bees are sugar junkies. Nectar fuels bees’ flight and warms them, allowing them to rev up their thoracic flight motors preflight and enabling a queen bumblebee to incubate her brood just like a mother hen.

But as we will discover, flowering plants and bees are not strict mutualists. Flowering plants don’t want to give up all their precious pollen to undesirable pollinators or even to generally dependable pollinating bees. A small fraction of a flower’s pollen grains must make their way to other flowers to ultimately produce seeds and foster new generations of plants. Bees, on the other hand, would like to collect all the pollen and not give any of it up. This leads to cheaters in the system. Some nectar-robbing bees cut slits or holes at the bases of tubular flowers and never deposit pollen on stigmas. They are anti-pollinators. Orchids and a few other flowering plants offer no food to bee pollinators. Instead, they dupe male bees into thinking a particular orchid flower is a receptive, ready, and waiting female of their species. Why not? They produce the same chemical scents and even sort of look like those female bees—at least to the eyes of a myopic male bee.

This trick works because bees have developed a diverse and intriguing array of adaptations when it comes to sex. Together, we’ll explore their interesting and mostly hidden sex lives. Many male bees are highly territorial and defend clumps of flowers from other males. There, they hope to mate with a female of their species. Carpenter bees in Arizona seek out prominent hilltops. In small groups, they display their presence by releasing a rose-scented sex pheromone. Females follow the scent uphill and decide which male to mate with. This is called a lek mating system, just like those in some birds.12 Honey bee drones fly high above the ground in drone congregation areas, following the scent of virgin queens, with which they mate in midair.13 Certain desert bees in the

genus Centris have two types of males. Larger males are diggers and warriors. These so-called metanders can smell virgin females waiting underground. After battling with other metanders, digger males excavate their partners and fly them to a nearby bush on which to mate. Smaller males adopt a less successful strategy of patrolling nearby plants in search of potential mates.14

Most remarkably, we now know that bees are sentient, they may exhibit self-awareness, and they possibly have a basic form of consciousness. Bees can feel pain and likely suffer. Some bees plan for the future by cutting resin mines into fresh bark, to which they return again and again. Others cut small holes in leaves, causing those plants to flower as much as a month earlier, to the benefit of the bees. They think and may form mental maps of their foraging routes. Bees remember the characteristic scents and shapes of their preferred flowers for several days. They make choices and can be easily trained to select and remember various colors or odors. They can navigate complex mazes and intuit other challenges as swiftly and efficiently as any rat or mouse. When presented with certain flowers, many bees innately know to use their powerful flight muscles to vibrate pored anthers, instantly releasing protein-rich pollen, which will be inaccessible to other bees or pollinators.

Bees can also learn to do highly unusual things such as pulling a string or rolling a ball to receive a sugar water reward. Maybe you’ve seen that YouTube video of bumblebees playing soccer.15 These are tasks they would never do in nature, but they might be surprising from a creature with a tiny brain housing just one million neurons (humans have at least eighty billion). Bees spend a good deal of time sleeping, during which memories are formed and stored in long-term memory just as in us. It may be impossible to ever know, but bees may even dream.

Bees do not perceive the world as we do. Their sensory systems would be entirely alien, and perhaps horrifying, to us if we could for but a moment jump inside their skins and experience their world. What would it be like to see polarized light patterns in the sky, or to see the invisible ultraviolet light patterns on flower petals, or to see electrostatic patterns left on flowers from earlier bee visits? What if we couldn’t see flowers unless we were a few inches from them? A bee’s vision is sixty times less sharp than our own. On the other hand, bees detect the microscopic

textures and patterns on flower petals, much as a blind person can read the tiny bumps in a printed Braille book.

Humans have been associated with bees and cared for them for millennia. By 3000 BCE, Old Kingdom Egyptians were keeping honey bees.16 Egyptian beekeepers navigated papyrus-and-wood barges up and down the Nile River containing mobile apiaries of honey bees in ceramic hives. They effectively followed the onshore bloom, and their bees made bountiful crops of honey. These were the world’s first migratory beekeepers. Atop the porous limestone of tropical forests in the southern Mexican states of Yucatán and Quintana Roo live social bees and their keepers. The ancient Maya tended these stingless Melipona bees, especially the royal or lady bee, as do the modern Maya.17 Here, highly social colonies of bees living inside log hives called jobones have been carefully tended for almost four thousand years. These stingless bees affix reflective white sand to their nest entrances as ultraviolet signposts to guide them home in their deeply shaded forests. Melipona worker bees also communicate with their nestmates using brief buzzes, sound pulses about floral resources.

Following in the footsteps of naturalists and scientists of the past, we’ll go into the field to locations around the world and into the laboratories of noted bee biologists and pollination ecologists. You’ll be introduced to the observations and experiments of innovative scientists who have unraveled the mysteries of bee vision, olfaction, taste, touch, learning, and memory, and bees’ astounding mental abilities.

My own first encounters with bees were as a high school student in Placentia, California, in the late 1960s. One important lesson learned was to work my honey bee hives only on sunny days and with proper personal protective equipment. Using a crowbar to tear into the walls of an old shed to remove honeycombs from a feral colony did not go well. The morning was a dreary gray, and a light drizzle had begun to fall, which I mistakenly hoped would mean a cooler, more relaxing experience. In painful hindsight, it must have been something about wearing trousers that didn’t cover my thin black socks, using a flimsy veil, and the fact that the bad weather had kept the ill-tempered guard bees indoors. They, however, were fully ready to explode, defending their sweet honey stores, as I cracked open the first board. My ankles received more than

one hundred stings, swelling to the size of footballs, and they itched for days. I discovered a lot about stimuli and bee behavior that fateful day.

As a college sophomore, a first trip into the Costa Rican dry deciduous forest of Guanacaste Province was my personal adventure, my biological Voyage of the Beagle. Later, I became a professional pollination ecologist with graduate degrees from California State University, Fullerton, and the University of California, Davis. Today, as a faculty member of the University of Arizona, I continue my research into buzz pollination, oil-collecting bees, and, most recently, the microbiomes living inside bees’ brood cells. It turns out that many solitary bees are getting as much nutrition, or more, by consuming microbes as by eating pollen. Every day spent in the Sonoran Desert of Arizona and Mexico presents unique opportunities to explore the minds and behaviors of bees. It is highly pleasurable and enlightening to watch bees interact with desert blooms and to mentor University of Arizona students and interact with faculty colleagues around the world.

I’ve trained bees to visit artificial and real flowers within indoor flight arenas. I’ve pointed a shotgun microphone at bees while they buzz pollinated roadside nightshade flowers in southeastern Arizona, and then analyzed their buzzes in terms of frequency, duration, and amplitude. I’ve watched bees stick out their tongues at me (the widely used proboscis extension response test) as my colleagues and I puffed test flower scents at them. In every possible way, my life has been a wonderful and fascinating journey into the private lives of bees while discovering some of their innermost mysteries.

We’ll now begin our journey of discovery into the minds, sensations, and experiences of bees both familiar and strange. Along the way, we’ll meet foraging, nesting, mating, and thinking bees of all types. Let’s fly with them.

Chapter 1 A Bee’s Life

The fuzzy brown bee awakens inside a dark underground burrow. She’s completed her nest, a den of open urn-shaped brood cells that will become the precious nurseries for her grublike larvae. She is a single mom with a family to feed. Our bee gets no assistance from her long-dead mate or from her sisters or other relatives. She isn’t part of a social collective, nor does she live within a compact wooden hive bursting with thousands of other bees. Her life is a brief, solitary existence, a few intense weeks spent foraging at flower patches, gathering food and provisions that will ensure her young will mature. Each morning, she flies from her earthen nest to locate distant flowers, which are like one-stop bee supermarkets. Bees need this hidden pollen and nectar, the food rewards that flowers offer in return for pollination services.

It’s a difficult and busy life. Her brain, though no larger than a poppy seed, can handle the complex thoughts and challenging celestial and landmark navigation that daily foraging requires. Every trip to a flower is a new learning experience, and she easily memorizes the flowers’ locations, colors, scents, and rewards. The bee navigates and actively chooses the kinds of flowers she visits, making use of her past

experiences and memories. She thinks, makes quick decisions, and learns for herself from her complex and ever-changing interactions with the environment.

On this typical morning, the mother bee scrambles up from the bottom of her deep nest to the soil surface, aided by little “kneepads” on all six legs. She pauses just below the surface, not daring to show even the tip of one antenna. There are many potential dangers outside the safety of her nest. There may be hungry wolf spiders, lizards, birds, or ferocious predatory insects such as robber flies nearby. Other insects, including parasitic bee flies, velvet ants (a kind of wasp), and parasitic blister beetles, are potent natural enemies waiting to enter a bee’s nest, to lay their own eggs while the owner is away.

She waits several minutes until the rays of the bright morning sun strike her face and warm her. Our female is about to fly. She inches forward and tests the air, both antennae waving frantically like stout fishing rods. Thousands of finely tuned microscopic sensory cells are embedded within each of the ten flexible segments (flagellomeres) of her antennae. Everything seems fine. Her sensory cells and the two mushroom body regions (areas that process complex information) within her brain signal an all clear. She doesn’t see or smell any nearby predator or parasite making a stealthy approach toward her burrow.

The female bee briefly shivers the powerful flight muscles within her thorax to warm up. Ready, she launches herself skyward and hovers in midair. Performing an aerial pirouette, she flies left, then back to the center, and then to the right of her nest. She repeats these back-and-forth, ever-wider zigzags, all while facing her nest and flying higher with each pass. In fact, she is memorizing the locations of the physical landmarks around her nest. These could be small stones, live or dead plants, bits of wood, or similar debris. She quickly creates a mental map of her home terrain. In less than a minute, she has memorized all the visual imagery, the spatial geometry, and the smells of her immediate surroundings. All sorts of solitary and social bees perform this instinctive behavior when leaving their nests, forming detailed mental maps of their homesite and nearby landmarks.1

Soon, our female turns and flies away from her nest at about 24 kilometers per hour (15 miles per hour) in search of flowers.2 Fragrant

blooms will provide her with the crucial pollen and nectar resources she needs to survive and provision her underground nursery. While she is foraging, the bee’s compound eyes detect and analyze the plane of polarization of sunlight spreading across the sky, even if the sun is partially hidden behind clouds. She knows the time of day by observing the relative position of the sun as it moves across the sky. This is the so-called sun compass. It is used by bees, ants, and wasps to keep time and navigate within complex spatial environments while walking or flying to and from their nests.3

Once our mother bee locates a promising flower—perhaps one she remembers from previous visits—she probes it for nectar, accidentally brushing against the flower’s plump anthers. She is dusted with gritty microscopic pollen, which contains large amounts of nutritious proteins, fats, vitamins, and minerals. And, like the blades of a Swiss Army knife, her special rake-like leg combs collect pollen from her body to transport home. She packs thousands of the powdery pollen grains onto the branched hairs of her hind legs. Once gathered there, they look like fluffy little orange saddlebags.

Now laden with pollen safely stored on her hind legs, and nectar inside her nectar stomach (the crop), she flies home using celestial cues including the polarization of sunlight and the sun’s position, along with her flight and wind speed. Her flying skills are all performed with a “navigational computer” inside her brain honed by evolution during millions of generations of ancestral bees before her. Putting on the air brakes at the last second, she searches for those previously memorized landmark cues, the bee signposts like colored airport runway lights guiding her safely back home. It’s quite an accomplishment for a bee only one centimeter (about one-half inch) long to make such long flights to distant fields of flowers.

Back inside her nest, the bee mixes the sweet nectar and pollen using her legs and mouthparts and then shapes a moist pea-size ball of “bee bread.” Turning away, she lays an egg from the tip of her abdomen, attaching the sausagelike translucent white egg to the food ball. The bee’s egg is smaller than a slender white rice grain. It won’t hatch into a tiny, slender larva for another three days. The pollen ball contains all the meals in one that the mother bee provides for each developing larva. In

fact, this is all the food she will provide to each offspring, everything they will require to grow from the egg into an adult bee.

Her work finished, the mother bee will soon die, never seeing or interacting with any of her offspring. Her progeny will be left to survive and defend themselves against destructive fungi, pathogenic microbes, predators, parasites, and the weather. The fat grubs will grow quickly and then transform into pupae. A few lucky grubs will emerge from their underground cells as healthy adults the following spring. These next-generation females will mate, forage, dig and provision nests, then ultimately die, linking endless bee generations that have been repeated over millions of years.

The belowground nest of a typical solitary ground-nesting bee (e.g., Melissodes). Off the main tunnel are side branches leading to larval cells. These brood cells contain pollen-plus-nectar, the food provision, upon which a single egg is laid. The bee larvae develop through four or five molts and eventually pupate. The next generation of bees typically remain underground until they emerge as adults the following spring.

The bee’s life I’ve just described is not unique. In fact, solitary ground- or twig-nesting bees are the rule, not the exception. Honeymaking, or social, bees in huge colonies are rare. Digging a nest and foraging at flowers for food are just two of the many behaviors that make bees incredibly fascinating creatures, like alien life-forms right here on planet Earth.

But one must wonder, what do bees and humans share in terms of behaviors, anxiety, and self-awareness? We can still see Aristotle’s lasting influence in some recent writing claiming that humans are unique among animals—that only we can think or reason, make and use tools, form abstract ideas, communicate with language, have self-awareness, dream, grieve lost family members, or contemplate our own mortality. Fortunately, these claims are being overturned as animal behaviorists, ethologists, and comparative psychologists expand their knowledge of the nonhuman world. Today, biologists understand that humans are not completely different from other animals. Especially in relation to cognition, sentience, and learning, we are enmeshed within a broad animal continuum, not better than or somehow set apart from the rest of the animate world.

In the pages that follow, we will find out about the many behaviors, both inborn and learned, that make bees an endlessly intriguing part of this animal continuum. At the same time, we will find out how the mere one million nerve cells in a bee’s brain respond to the sensory input of their world, how they learn, remember, and make decisions.

Bees, Ants, Wasps: What Is a Bee?

Before we get inside bees’ minds, we need to understand a little bit about their family tree. Bees, along with sawflies, ants, and wasps, are grouped by entomologists into one large insect order, the Hymenoptera, named for their membranous wings. There are more than 117,000 Hymenoptera species in total, originating in the Triassic period.4 Their closest relatives are the true flies, butterflies, and moths. Most Hymenoptera lead solitary lives, although some, such as ants, are entirely social. Colonies of social insects can be massive, including underground fungus gardens of South American leaf-cutter ants (Atta) or African driver ants (Dorylus),

whose swarming colonies may contain over twenty million individuals.5

The Hymenoptera share several evolutionary characteristics. They have four wings joined together in flight by a series of small hooks; thus, the wings beat as a single, broad unit. Hymenopterans have three body segments: the head, thorax, and abdomen. Typically, the forward part of the abdomen is narrowed, often dramatically into a “wasp waist.” Some might recognize these flying insects from a past close encounter of the stinging kind. They possess a sharp sting that is used either to inject venom to paralyze prey for larval food or as a painful defensive weapon against vertebrates or other insects.6

Bees have an internal storage organ, the honey stomach, used for transporting nectar back home. They are also fuzzier than most wasps and have shaggy hind legs. The single defining feature that separates bees from wasps is the branched, almost featherlike, hairs on bees’ bodies. Wasps have simple, straight hairs that are unbranched. Bees’ branched hairs evolved to catch, hold, and transport pollen grains. Dense tufts of these plumose hairs on their hind legs, abdomens, and other body regions allow bees to efficiently collect and transport pollen back to their nests.

Bee Origins

Bees are mainly herbivores, mostly vegans. They don’t munch green leaves as do grasshoppers, caterpillars, or roaming herds of African antelopes, but they do eat plant materials: pollen, nectar, and sometimes floral oils. (About 10 percent of living bee species do eat a bit of meat on the side, and we will explore their lifestyles later.)7 But bees have a secret past. The ancestors of the world’s bees and their closest relatives are supremely adapted carnivorous predatory wasps. Most wasps chase down prey (spiders, flies, beetles, caterpillars) and paralyze them to provide always-fresh living food for their offspring.

How did the earliest bees switch from being waspish carnivores to their present-day mild-mannered herbivorous lifestyles? Although it may seem like a simple question, it was a mystery until recently. To answer, we need to go back to the Mesozoic era, 252–66 million years ago (mya). The Mesozoic was a time of dinosaurs, giant flying pterosaurs,

and toothy marine reptiles, along with diminutive early mammals. It was also a verdant world clothed in strange plant groups—now mostly extinct—that we likely would not recognize today. Soon, flowering plants (the angiosperms) would add swaths of vibrant color to mostly brown and green terrestrial landscapes. Their new sexual invention, flowers, would also provide unique and welcome food to the world’s earliest pollinating animals.

Gymnosperms—plants bearing naked seeds shed from cones (think of pine and fir trees)—were among the early and dominant land plants before the appearance of the angiosperms. These early gymnosperms produced male cones and lots of pollen but only small amounts of nectar. Still, the pollen and early nectarlike secretions provided food for some of the earliest pollinators, including beetles, flies, and small wasps.

Tiny fringe-winged insects with piercing, sucking mouthparts known as thrips (about six thousand species in the order Thysanoptera) also arose during this time. These millimeter-long winged adults entered flowers and fed on petals or directly upon pollen grains, sucking them dry as if they were fat ripe grapes. Thrips are extremely common insects even today and are familiar to gardeners as nuisance pests. It is almost impossible to shake out a flower anywhere without thrips also tumbling out along with the pollen.

In Cretaceous habitats, small predatory wasps hid and hunted inside flowers for even tinier prey animals. These long, slender black wasps were only 2–4 millimeters (0.08–0.16 inch) long. Members of the Crabronidae family, like the “sand wasps” along shorelines or the so-called bee wolves that hunt and eat bees (Philanthus), they belonged to the Ammoplanina group, also called pemphredonine wasps. In the Cretaceous period as today, the ammoplanines made their living by visiting flowers and hunting their favorite food: thrips. We know this to be an ancient relationship because fossilized thrips are associated with fossilized cycads, early seed plants. Some of these individual fossilized thrips carried up to 140 cycad pollen grains on their bodies.8 There are also pemphredonine wasps exquisitely preserved in amber from Burma (Myanmar).

German scientist Manuela Sann and her colleagues proposed that the early Cretaceous proto bees likely fed on thrips and that the thrips’

bodies were coated in pollen, giving the early bees an extra protein snack. These earliest bees gave up chasing difficult-to-catch flying prey and visited flowers instead. Eventually, they switched entirely to a diet of pollen and nectar. This elegant idea built upon a theory first proposed by Russian entomologist S. I. Malyshev almost fifty years ago and is now widely accepted.9

Oldest Fossil Bees

Bees are an ancient animal lineage. They first appeared in geological history during the early Cretaceous, about 130 mya.10 Their close ecological associations (mutualisms) with flowering plants are also ancient, although flowering plants evolved a bit earlier, perhaps 140 mya.11 Fossilization is nature’s lottery. It is estimated that as many as one hundred million animal and plant species may have lived since life originated on Earth. All organisms die, but the rarest fraction (perhaps as few as 0.001 percent of all species that have ever lived) have, by chance, been preserved for the ages as fossils in mostly sedimentary deposits. When an animal or plant dies, it typically completely disintegrates and is therefore lost from what is a very spotty and incomplete record of life on Earth.

If, however, an organism dies and falls into the muck at the bottom of a pond or becomes trapped inside globs of tree resin, that organism might just be “lucky” enough to be entombed as a fossil for millions of years. Then, after eons of wind or water eroding away upper stratigraphic layers, someone—perhaps an amateur collector or a professional university paleontologist—might discover and study the fossil. Such is the case with a limited number of bee fossils that have been discovered and named by paleontologists.

Designation of the first true bee comes from just such a unique and solitary find, a bee preserved in gemlike amber, the fossilized resin of ancient conifer trees. The oldest bee known to science is Cretotrigona prisca. On an unknown day and year during the 1920s or 1930s, Alfred Hawkins found the fossilized bee in a clay pit quarry for brickmaking near Kinkora, New Jersey. Small pieces of amber containing fossil insect and plant inclusions have been found in this area, including the first Cretaceous ant (Sphecomyrma). The piece of amber was given to Columbia

Line drawing of the first true fossil bee, a stingless bee worker (Cretotrigona prisca) in Cretaceous amber about 65–70 million years old, from Kinkora, New Jersey.

University and transferred to the amber collection at the American Museum of Natural History in New York City, where it was carefully studied for the first time in the 1980s.

This oldest fossil bee was originally described in 1988 and named Trigona prisca by the late Charles Michener of the University of Kansas and David Grimaldi of the American Museum of Natural History. The yellow piece of amber containing the bee is about one centimeter in size and has lignite coal attached to one side. Michener and Grimaldi estimated the age of the fossil to be as young as 74 million years or possibly as old as 96 million years, making this the oldest fossil bee known, tens of millions of years older than the other known bee fossils.12

The Kinkora specimen is a female with a small abdomen and a distinctive pollen-transporting apparatus called the corbiculum, or pollen

basket. She is a member of the widespread tropical group of truly social bees, the honey-making stingless bees, or meliponines, in the honey bee family Apidae. The fossil bee is unusual in many respects. First, she is a social bee, one of about four hundred species of stingless bees worldwide that today live in large colonies inside rot cavities within living trees. The problem for our Cretotrigona fossil in amber is that evolutionary biologists believe that solitary ground- and twig-nesting bees evolved first, and large-scale sociality and big colonies followed. Instead, here was a full-blown social honey-making bee as our earliest known specimen.

It was an unlucky accident for the Kinkora bee to become fatally trapped in sticky amber resin but extremely lucky for paleontologists. Generally, stingless bees are masters at handling sticky resins and don’t become entombed. Small flies and other insects are weaker and more likely to become ensnared. Worker stingless bees will often return day after day to the same “resin mine” gash on a tree, harvesting the resins and using them as essential building materials within their nests. The bees form pillars and sheets of wax plus resin (cerumen) and construct their brood cells and honey and pollen storage pots of the waxy resinous mixture. Stingless bees are master animal architects, sculptors using the wax they secrete and resins from forest trees to create their amazing living spaces. The resins also afford a chemical barrier against pathogenic bacteria and fungi that might spoil their stored food or attack vulnerable larvae.

When the Kinkora specimen was restudied by paleontologist Michael Engel in 2000, he described it as a new genus (Cretotrigona), and the age of the amber was revised upward to 65–70 million years. Still, Cretotrigona is currently the only specimen of a true bee from the age of dinosaurs. A lucky collector may yet locate additional fossil bees in Cretaceous amber deposits from New Jersey, Lebanon, or Myanmar.13

Since the discovery of the Kinkora bee, we’ve found one older proto bee from a different Cretaceous amber deposit. In 2006, researchers George Poinar and Bryan Danforth published their description of an early bee relative in amber dating to the early Cretaceous period (approximately 100 mya) from Myanmar.14 They named the unique fossil Melittosphex burmensis. The genus name indicates a mixture of

bee and wasp characteristics. Interestingly, the fossil bee is a male but has branched featherlike hairs on his head and hind legs, just like those found on female bees today. The little Melittosphex, 3 millimeters (0.12 inch) long, has some wasplike characteristics, including thin hind legs without the spines bees have. Thus, Melittosphex burmensis appears in the same clade (a group of organisms evolved from a common ancestor) of bees. But it is a proto bee rather than a true bee. Unfortunately, there are no female specimens, so we do not know whether Melittosphex bees carried pollen back to their nests.

Bee Sex, Reproduction, and Life Cycles

Bees, ants, and wasps have a peculiar form of sex determination, different from most other animals. A honey bee worker is the sterile female offspring of the queen. A male bee, a drone, is also the offspring of the queen but has an entirely different genetic makeup. Male honey bees have a mother but not a father. Furthermore, they have a maternal grandfather and grandmother but do not have paternal grandparents, and males cannot have a son. Sounds confusing, right? Well, it is. The genetic sex determination system in bees, ants, and wasps is called haplodiploidy. It has developed in some insects, mites, nematodes, and rotifers, in about 12 percent of all animal species.

Female offspring are produced from the fertilized eggs laid by queen bees. They have a normal diploid complement of a double set of chromosomes, one set from each parent. Males, however, result from the queen laying an unfertilized egg that has only her set of chromosomes. They are haploid, N instead of 2N like you and me. This is true for the males of all the world’s bee species, not just the eleven or so species of true honey bees in the genus Apis. Haploid males also produce identical sperm containing 100 percent of the father’s genes. Haplodiploidy isn’t always a precursor for the evolution of social lifestyles, but it seems to have played a major role in social species arising in bees, ants, and wasps. Sponge shrimp, naked mole rats, and all termites have evolved sociality and have normal (diplodiploid) sexual determination.

There are genetic advantages to haplodiploidy. Male bees are related to one another by 50 percent. The average relatedness among sisters in

haplodiploid species is 75 percent, meaning that sisters are more closely related to one another than to their mothers or daughters. According to kin selection theory, it may be easier for altruism to develop in animals with a haplodiploid sexual system. Individuals should be more willing to lay down their life for a close relative, such that they may die but their genes will spread in future generations.

Let’s now explore the biology of bees and how they make their living. This forms the basis for everything that happens inside a bee brain, along with the environmental forces that have shaped bee intelligence over the past 130 million years. The life cycle of all bees includes four developmental stages in what is known as complete metamorphosis. These stages are egg, larva, pupa, and winged adult. The egg hatches into a small wormlike grub in about three days. The larva feeds voraciously upon the pollen mixture the mother provides. At the end of the larval feeding stage, the larva defecates and may or may not spin a silken cocoon. Then the larva stiffens and becomes a prepupa. Finally, there is a dramatic transformation into the pupal phase. This is the overwintering phase of the life cycle. It isn’t until the following spring that the prepupa becomes a pupa and the legs and wing pads of the adult bee can be clearly seen. The pupa darkens in color from white to black, and the adult bee emerges from within the pupal skin. The new adult usually remains inside its cell for several days before chewing its way out. It digs upward through the loose soil in the tunnel and exits the nest. Male bees typically emerge before females and begin to feed and to look for virgin females as mates, often on the surface of the emergence site or by patrolling at nearby flowers.

As we learned from the female bee that introduced this chapter, most of the world’s bees are solitary females, nesting and provisioning their nests without any help. They excavate mostly earthen nests that are vertical tunnels with side branches leading to rounded brood cells. Females spend a lot of time creating these cells and polishing them before placing a pollen-nectar ball in each one and laying an egg. Each female bee instinctively knows how to dig her nest and form brood cells. She does not have to learn this complex behavior. The nest architecture is uniform within a species and similar within the same genus of bees. She excavates, shapes, and provisions about one cell per day. Depending upon the

kind of bee, the nest may contain one or more than a dozen cells. During her lifetime, a female may construct several nests.

Bee Diversity and Lifestyles

Diggers, carders, leaf cutters, masons, carpenters, cellophane makers, and more: these are just some of the nesting and lifestyle choices made by the world’s bees, an incredibly speciose and diverse group of animals. Females of most solitary bees are ground nesting. Their nests may be as shallow as a few inches or deeper than a human grave. These bees excavate burrows and shape and polish the urn-shaped brood cells that will hold a play-dough-like mixture of pollen and sweet nectar, and one precious egg.

Although nest making and cell building are instinctual behaviors, there is tremendous diversity in the architecture of bees’ underground nests.15 They can branch off in side tunnels, can conceal hidden chambers, and may contain one to dozens of larval cells. The brood cell chambers are often distinctively shaped but always—a bee group trait—have a characteristic roof, a spiral closure fashioned from moistened soil particles.

Occasionally, you may have noticed pieces of green leaves stuffed inside nail holes in wooden planks or fence posts around your home. These holes are the telltale handiwork of female leafcutter bees, in the family Megachilidae. Gardeners know them, too. In less than a second, a female leafcutter can snip an oval piece from the edge of the leaf of a prize rosebush or another tender-leaved plant and fly off with it. Once the bee is back inside her rented tunnel nest (an abandoned tunnel left by wood-boring beetles), she uses these leaf pieces as wallpaper to line the burrow. They form the cells in which the larvae develop. The chemicals inside the leaves may provide protection from fungi and other microbes that might otherwise attack the growing immature bees. Most leafcutter bees are known as renters, since they don’t create their own nests.

Leafcutters may even use the supple and colorful petals from large flowers. This makes their brood cells quite attractive, even artistic. We don’t know whether bees have artistic sensibilities, although some are known to “decorate” their nest entrances with pollen or sticky seeds, the latter of which may offer chemical protection from ants. Certain

mason bees carefully select empty snail shells as handy bee homes. Some tropical stingless bees (Melipona) collect brilliant white sand and add it to their funnel-like nest entrances. The sand serves as a reflective ultraviolet light beacon, guiding foragers home in the dim light of the forest understory. Other bees in the megachilid family return home with sticky resins, sand, and small pebbles as handy building materials. Mason bees visit the edges of ponds and gather up little mud balls. They fashion these into the walls and roofs of their nests, not forgetting to make spiral closures at the top end.16 And carder bees use their specialized mandibles to rake through and snip off delicate white plant hairs (plant wool known as trichomes) and bring this material home. There, they smooth and shape the plant fuzz into the cells of their nests.

Arizona carpenter bees, true to their name, excavate wide tunnels inside dead but not rotted wood of century plant (Agave), yucca (Yucca), or sotol (Dasylirion) stalks or dead branches or tree trunks. They use their massive mandibles like sharpened wood chisels to carve out their wooden abodes. Once the linear tunnels are lengthened and smoothed, the female bees add waferlike partitions between the individual cells. These bees use their excavated waste sawdust particles to form their cell partitions. In effect, they are creating concave particleboard walls separating their larvae from one another. Bees invented particleboard long before humans did.

Along with their skills in construction and design, many bees are impressive chemists. Cellophane bees (in the family Colletidae) secrete chemicals called lactones that are enzymatically zipped together into powerful interlocking water-resistant molecules, like their own retro polyester leisure suits. Their cell linings are cellophane-like not only because of their thin transparent nature but also because their chemistry is identical to that of man-made cellophane! In many instances, bees have created certain types of molecules long before human chemists ever thought of doing so. Certain so-called digger bees often line their burrows and cells with waxy secretions that waterproof them.17

Bees are also artists in wax. They may not create encaustic paintings, but they did evolve wax-secreting glands millions of years ago. Today, honey bees, stingless bees, and bumblebees secrete pure white beeswax from specialized glands underneath their abdomens. Worker bees

fashion these tiny wax scales together by adding saliva and perhaps other secretions to the wax. They shape the wax into elaborate pollen- and nectar-containing storage pots, egg shaped in the case of bumblebees and stingless bees or the famous double-sided hexagons of honey bee combs. Bees don’t get out their protractors and compasses to produce the exact angles within their famous hexagonal combs. We’ll discover what really happens in another chapter.

All social bees biochemically convert the sugars in floral nectar into wax inside their bodies. For honey bees, these waxen combs become storage pantry, dance floor, and nursery, forming the architectural room dividers of their nests. Wax is precious and energetically expensive for bees to make. They recycle every bit of it. Wax is white when first secreted but browns with age, becoming almost black as a result of contaminants including pollen, feces, and the silk from many bee cocoons. Beekeepers simply cut off the tops of sealed honey combs, spin out the honey, and then recycle the waxen frames back to their bees for them to use again. A secret ingredient of famous Stradivarius violins comes from the waxand-resin mixture originally gathered by stingless bee colonies living in the Amazon rain forest.18

Although they are fascinating examples, wax sculptors and comb makers aren’t the norm in the bee world. As we’ve learned so far, most bees dig earthen nests and live solitary lives. They eat mostly pollen and nectar, navigate using landmarks and solar clues, and have adopted a wide array of remarkable behaviors, both instinctual and learned. But what guides these behaviors in the world’s bees? And how do they do so much with so little?