If you've watched Season Four of Arrested Development or read any of the numerous alarming mainstream media reports on bees , you've heard of colony collapse disorder (CCD). While a variety of factors have been shown (or postulated) to play a role in CCD, the outcome is consistently the death of the honeybee colony.

"Oh no!" you say. "No more honey!?"

But what you should be saying is, "Oh no! No more food!"

One of the things that I needed reminding of, given the number of years separating me from a biology class, is that plants flower as part of a sexual reproduction process in which pollinators like hummingbirds and, yes, honeybees serve as a go-between. Plants can't carry their genetic materials to each other, so pollinators (and occasionally the wind) do it instead. Birds and bees feed on the nectar contained in a flower, inadvertently accumulating pollen on themselves, and move on to the next flower for more nectar. Transfer of pollen is the plant equivalent of fertilization of an egg, and the fruit that eventually grows is a sort of plant uterus, harboring the seeds safely in the a pocket of nutrition necessary for the germination process. No pollinators means that when flowers whither and die, no fruit grows, and no seeds develop. No apples, no pears, no oranges. No onions or brussel sprouts. No cotton or cocoa. Imagine what your life would be like without those foods and products, among the many other agricultural products that bees pollinate.

Enter the solitary bee, a bee quite different from the honey-making, swarming, hive-dwelling Apis that people most commonly think of. Solitary bees in the genus Osmia make no honey. They live in single-bee dwellings and interact with each other only to mate. Their isolated lifestyles make them much more docile than their honeybee cousins: they have no colony to protect and therefore no interest in self-sacrifice for the benefit of the hive. In fact, males are incapable of stinging, and among the females that are capable and that are sufficiently goaded, the sting is is anecdotally no more painful than a fly bite. Osmia also happen to be remarkable pollinators. In fact, they are, bee-for-bee, far better pollinators than their honeybee cousins, both in terms of pollination quality and quantity (they can visit up to 22,000 blossoms in just fifteen days). In fact, as few as 250 solitary bees can do the job of an entire hive of honeybees, which contain tens of thousands of individuals. And, perhaps most critical of all,  because they don't live in colonies, they don't suffer from CCD.

So, why, you may ask, aren't farms using solitary bees for crop pollination? One reason is that honeybees are something of a traveling circus. Plenty of farms and orchards keep their own bees, but many rent bees (at ever increasing cost) for the few weeks a year when they require pollination. That system allows the professional farmers to do the farming and the professional beekeepers to mind the bees, besides which, it keeps the bees busy as they're ferried from one food supply to the next. Solitary bees fly for only 4-6 weeks before succumbing to old age, so their utility as pollinators expires before they have a chance to move to another crop. The next generation of solitary bees will develop for a full year before emerging to pollinate the same crop their parents did the year before. Honeybees also have a commercial advantage in that they produce a commodity - honey - while they're doing their pollinating business, whereas solitary bees produce only enough foodstuff to provide each of their larvae with the nutrition necessary to grow into next year's bee.

Those factors were considerable advantages for honeybees until they started dying en masse. Now, solitary bees are now beginning to look a good deal more attractive. As I mentioned earlier, 250 solitary bees can replace a hive of honeybees, and because both possess a similar foraging range, bee condos (more on these later) can replace hives on a roughly one to one basis. Their seasonal pollination habits mean that they can (must) be kept locally rather than being ferried among food sources, and temperature control of the cocoons can ensure that they emerge at just the right time to pollinate the crop that a farmer grows. Each female produces, conservatively, about ten females to replace herself. In nature, that would ensure a stable population, but in a managed bee population with close to 100% survival rate of cocoons, a farmer could have 10,000 (female) bees in five years, enough to replace as many as 2 millionhoneybees in terms of pollinating potential, having started with just a mating pair (note that females, who are making pollen balls to feed larvae, are the primary pollinators). Don't get me wrong, keeping 10,000 solitary bees is a bear of an undertaking, but then this is a huge portion of the world's food supply that we're talking about.

So what are bees condos? What does it mean to 'keep' Osmia? And who are these little loners, anyways?

Osmia are solitary but gregarious bees native to North America, unlike European honeybees, and include ground-nesting and hole-dwelling species. Their ability to be solitary relies on the fertility of every female, whereas in hive-dwelling communities, only the queen reproduces. Because they don't protect a queen and the hive's honey, they are non-aggressive, and the females will only sting if trapped or squeezed. They are classified as gregarious because they choose to live and build nests in proximity to each other, probably to maintain genetic diversity when mating. In terms of crop pollination, the most important players are orchard blue mason bees and (foreign but now naturalized) hornfaced bees. Leafcutter bees, which are from the genus Megachile , are also commercially important (and also naturalized foreigners). These are the three species I'm really referring to when I write 'solitary bees,' although there are many, many more.

The first step in keeping solitary bees is providing them with a domicile, a 'bee condo.' Mine looks like this:

Bee Condo
Bees sleep in the holes overnight, when it's too cold for them to fly, and use them as a safe place to amass pollen and lay eggs during the day. After fertilization by males, who obnoxiously hang out in on the condo's 'stoop' all day hoping to score, the female collects sufficient pollen to provide one larva with food for development and lays a single egg with the pollen ball. She then builds a wall of mud (hence 'mason bees') or leaves ('leafcutters,' get it?), sealing the cell, and fills the next compartment with it's own pollen ball and egg. She might finish several dozen such compartments before dying, having strategically placed the males at the front of the tube so that they can snag a female on her way outs. Meanwhile, the eggs will have hatched within a few days of being laid, and the little larva will be chowing down on the pollen ball that mom left them. They go through the larval and pupal stages and then spend the winter cocooned in their compartments.

In nature, obviously, the bees don't have the luxury of a condo. Instead they use hollow reeds or naturally-occuring holes bored by insects or woodpeckers. Their numbers suffer from infestation by parasitic wasps, spread of mites (which eat the pollen balls and starve larvae), predators like woodpeckers, etc. In a human-managed population, however, these challenges are mitigated by physically protecting the condo from parasites and predators once all the females have died (and thus all the eggs have been laid) either by moving the condo indoors or by covering it with mesh. As winter approaches, the cocoons can be removed from the condo and gently cleaned in water to remove mites and pathogens like mold spores. Cocoons are overwintered in a humid container kept in the refrigerator, eliminating the risk of early emergence during a warm spell. When daytime temperatures reach optimal levels (or crops approach their flowering state), the cocoons are simply placed outside. The bees will emerge on their own, and the cycle continues.

In the next post, I'll go into what to do if you want bees of your own to improve the yield of your garden, to safeguard our agricultural future, or to keep you company. I'll include plans for a condo and sources of bees. If you absolutely must read more right now, I highly recommend sections of Bee Pollination in Agricultural Ecosystems, fragments of which are available free of charge from Google Books.