If you don't look for bees, you probably don't see them. At least not many of them. Sure, you might notice a honeybee, or a bumblebee, the generic names we use for the most well-known species -- but there are more than 4,000 bee species in North America alone. Some are as large as bumblebees, and others smaller than a grain of rice. Most live solitary rather than hive lives; many are blue or green, not striped black and yellow. Their incredible diversity goes largely unrecognized -- but not to Sam Droege. As head of the U.S. Geological Survey's Bee Inventory and Monitoring program, Droege spends his days capturing bees, taking their pictures, and learning all he can about creatures responsible for pollinating much of the vegetal world. "We don't know much about these other species, even though they are lovely in their many forms, and very diverse. Just the sizes and shapes and colors are awe-inspiring," said Droege, who on the following pages introduces WIRED to his bees. Above: Augochloropsis metallica This splendid Augochloropsis metallica was collected on a tomato plant in a garden in Laurel, Maryland.

Agapostemon angelicus Contrary to popular belief, most bees don't sting people -- and that makes it easy to overlook them, said Droege. "Part of the reason we know so little about our native bees is because they don't sting us," he said. "If they were stinging all the time, we'd know a lot more about them." Male bees, like this male Agapostemon angelicus, don't even have stingers.

Megachile lanata Bees are synonymous with hive communality, yet honeybees and bumblebees are social exceptions. Nearly all of North America's bees are in fact solitary creatures, living in burrows dug in soil, holes in wood, old beetle holes and even hollowed-out grass stems. Megachile lanata is a newcomer to North America. It arrived in Florida in the 18th century as a stowaway living in holes in the timber of ships.

Halictus ligatus "Sweat bees are the most common," said Droege of bees that, in addition to feeding on nectar and pollen, are attracted to the salt in mammalian sweat. "They will come and lick the sweat off you. There are thousands of them nesting in every lawn. They're solitary, and they don't defend their nests. After we've tromped on their nests or dug them up, they just leave." Sweat bees belong to the Halictidae genus, common everywhere but Australia and Southeast Asia. This pollen-covered H. ligatus comes from the Morris Arboretum in Philadelphia.

Anthidiellum notatum Even bees that do sting often cause no trouble to us. "Their stings are very innocuous," said Droege. "The venom in a sweat bee is designed to repel another bee, or another kind of insect. Whereas the venom in a honeybee is designed to be injected in mammals, to keep you away from all those lovely grubs or honey stores." The pea-sized Anthidiellum notatum collects pollen for its nests from, appropriately enough, plants in the pea family.

Cemolobus ipomoeae Asked why there are so many different shapes and sizes of bees, Droege replied, "Why are there so many sizes and shapes of flowers? If there was just one honeybee in the world, the flowers could just be big open platforms. But reality is nowhere near that simple." Bees and flowers have co-evolved, often forming very specific and mutually beneficial relationships: a certain lineage of flower might try to keep out every type of bee but one, offering them a guaranteed source of food in exchange for the pollination they provide. Cemolobus ipomoeae specializes in collecting pollen from native morning glory plants.

Osmia distincta To detect the scent of flowers, the olfactory senses of bees are exquisitely sensitive and specialized, capable of detecting molecules in parts-per-trillion concentrations. "If you're a bee, you're using your antennae. The analogy would be a nose, but way, way more sensitive," said Droege. "There are all sorts of antenna sizes and shapes and designs. They're differentially sensitive to different molecules. They're primed to smell different things." Penstemon plants are a favorite of Osmia distincta.

Lasioglossum havanense As well as they sense smells, bees rely just as much on their eyes, which can spot from a distance such subtleties as a fringe of color on a petal, signaling the availability of pollen. "Antennae are thought to be a secondary mechanism. The first one is color. They'll go to different flowers, then use the scent as the return mechanism," said Droege. This Lasioglossum havanense was found in the Dominican Republic.

Perdita luteola Droege is perpetually amazed at the tendency of bees to show up almost anywhere: out in a southwestern salt pan, miles from the nearest plant life; in parking lots at FedExField, where the Washington Redskins play; in the middle of cities. "If there's a bee that specializes in squash, and you have a pumpkin on the third-floor veranda of your apartment, you'll get pumpkin bees," he said. Perdita luteola, found in deserts of the U.S. southwest, is "so small that it could fit inside a honeybee's abdomen," said Droege.

Bombus griseococolis The precipitous decline of honeybees -- some 30 percent of all commercial colonies died last year -- has elicited despair from farmers and concern from the public. Rather less attention, though, has been given to bumblebees, many species of which have declined dramatically over the last several decades. Bombus griseococolis, found across the United States, has fortunately remained common.

Agapostemon splendens Bumblebees aside, are other native bees declining? We just don't know, said Droege. Bumblebees are well-known, and their decline has been so extreme that "a baby could have figured it out," he said, likening the statistical analyses involved to "saying that we killed all the bison except for a handful in Yellowstone." Continued Droege, "there are probably groups of bees that may have had just as precipitous a decline, but were not so common or charismatic as bumblebees." Agapostemon splendens lives in the sand dunes of the U.S. East Coast.

Anthophora affabilis Pesticides, parasites and diseases have all been implicated in the demise of both honeybees and bumblebees, but the great threat to most native bees, said Droege, comes from habitat destruction: not necessarily the obvious, pave-and-destroy sort, but the type that produces superficially green landscapes which are actually oversimplified and biologically impoverished. "A corn field only provides one plant. Then, along the verges, we've overmanaged everything," he said. Not only are industrial farming regions inhospitable to bees. Roadsides are planted with fast-growing but homogeneous and non-native grasses. Weeds that make vacant lots come alive are eradicated as messy eyesores. Lawns and gardens and parks are trimmed and mulched. "We have herbicides and power mowers, so we're going to use them. We think, 'Wouldn't it be great if the entire world looked like picture-book houses?' And that kind of environment is just a train wreck for animals," Droege said. "If your objective is to have it look nice, and nice means everything is uniformly trimmed and symmetrical and fits that picture, that's great. If your objective is also to provide homes for plants and animals, then let some of these areas grow." Anthophora affabilis bumblebees, like this one from South Dakota's Badlands National Park, sip nectar and take pollen from flowers with deep throats.

Hylaeus volatilis What does it mean to lose bees? Is it meaningful according to relatively spiritual principles -- an aesthetic appreciation of biodiversity, a sense of duty to nourish rather than diminish life -- or is the loss utilitarian, too? Given that bee pollination is crucial to some one-third of all crop production, and that native bees often supplement the activity of commercial honeybees, there's a dining-table immediacy to bee declines. Yet there's another, subtler danger, said Droege. As bees are lost and flowers go unpollinated, or as flowers are lost and bees starve, interactions between plants and animals dwindle. These relationships are ecologically foundational; take this away, and ecosystems become more fragile. "There's a bunch of papers looking at diversity and health and robustness. If you've got a highly connected, biodiverse set of habitats, it's more resilient to injury. If something comes in, weather or climate or manmade disturbance, and whacks the system, the recovery rate is higher," said Droege. "It's like a house: knock out enough walls, and then it's not functioning anymore. Removing these bees, pulling out that last stick, could be what kicks the system into a new state. At that point, you have a pile of bricks." Hylaeus volatilis, seen above, is one of 60 bee species native to Hawaii. Many are now rare or extinct.